short essay on diversity in plants

Essay on Diversity in Plants

Students are often asked to write an essay on Diversity in Plants in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

Let’s take a look…

100 Words Essay on Diversity in Plants

Introduction.

Diversity in plants refers to the wide range of different plant species found on Earth. This diversity is essential for life as plants provide oxygen, food and habitat.

Types of Plant Diversity

Plant diversity can be classified into three types: genetic, species, and ecosystem. Genetic diversity refers to variations within a plant species. Species diversity is the variety of different plant species. Ecosystem diversity means the assortment of ecosystems that plants create.

Importance of Diversity

Plant diversity is crucial for the survival of all life forms. It helps in maintaining ecological balance and provides resources like food, medicine, and raw materials.

Threats to Plant Diversity

Human activities like deforestation, pollution, and climate change pose significant threats to plant diversity. It’s vital to protect and conserve our plant diversity for a healthy planet.

250 Words Essay on Diversity in Plants

Diversity in plants, also known as phytodiversity, is a fascinating field of study, encompassing the broad spectrum of plant species and their unique characteristics. It plays a pivotal role in the planet’s ecological balance, influencing everything from climate regulation to food chain dynamics.

Phytodiversity: An Overview

The world is home to an estimated 391,000 species of vascular plants, showcasing the incredible diversity of plant life. This diversity is not evenly distributed; tropical regions, for example, are hotspots of phytodiversity, due to their favorable climatic conditions and rich soil.

Genetic Diversity and Evolution

Genetic diversity is a key component of plant diversity. It allows for natural selection and evolution, where plants with beneficial traits survive and reproduce. This leads to the evolution of new plant species over time, further enhancing biodiversity.

Ecological Significance

Plant diversity is crucial for ecosystem health. Different plant species play varying roles in their ecosystems, from primary producers to climate regulators. They also provide habitat and food for numerous animal species, maintaining the intricate balance of nature.

Threats and Conservation

Despite its importance, plant diversity is under threat due to human activities like deforestation and climate change. It’s imperative for us to conserve this diversity, as it holds the key to sustainable development and the overall health of our planet.

In conclusion, plant diversity is a testament to the richness and complexity of life on Earth. It plays a crucial role in maintaining ecological balance and holds potential solutions to many of the challenges we face today. As stewards of this planet, it’s our responsibility to protect and preserve this invaluable resource.

500 Words Essay on Diversity in Plants

Introduction to plant diversity.

Plants, from towering trees to tiny mosses, play a crucial role in our planet’s ecosystems. They are the primary producers, converting sunlight into energy through photosynthesis and providing a food source for a myriad of species. However, this fundamental role is only one aspect of their importance. The diversity in plants is a fascinating topic, revealing the intricate adaptability and resilience of life on Earth.

Understanding Plant Diversity

Plant diversity encompasses the variety of plant species and the genetic variability within these species. Currently, scientists have identified over 390,000 species of vascular plants, with the actual number believed to be significantly higher. This diversity is not evenly distributed; certain regions, such as the tropics, are hotspots for plant diversity due to their favorable climatic conditions.

Diversity is not limited to species alone. Genetic diversity within a species allows for adaptability and survival in changing environments. For instance, a plant species with a broad genetic base will have a better chance of surviving a disease outbreak than a genetically uniform species.

The Evolutionary Perspective

Plant diversity is a testament to the evolutionary processes that have shaped life on Earth. Over millions of years, plants have evolved to adapt to a broad range of environments, from arid deserts to waterlogged swamps. This adaptability is evident in the diverse morphological features of plants, such as the water-storing stems of cacti or the insect-trapping leaves of pitcher plants.

The evolution of flowering plants, or angiosperms, is a key event in the history of plant diversity. Angiosperms are the most diverse group of land plants, with over 300,000 species. Their success lies in their unique reproductive strategy, which involves attracting animals to aid in pollination, thus enhancing their chances of reproductive success.

Importance of Plant Diversity

Plant diversity has immense ecological, economic, and cultural significance. Ecologically, diverse plant communities contribute to ecosystem stability and resilience. They support a variety of wildlife species, maintain soil health, and play a vital role in the carbon cycle.

Economically, plant diversity is the basis of numerous industries, including agriculture, forestry, and pharmaceuticals. Many of the foods, medicines, and materials we use daily originate from diverse plant species.

Culturally, plants hold significant value in many societies. They feature in art, mythology, and religious practices, and many indigenous communities have intricate knowledge systems centered around local plant diversity.

Conservation of Plant Diversity

Despite its importance, plant diversity is under threat due to human activities such as deforestation, habitat destruction, and climate change. These threats highlight the need for conservation efforts. Protecting plant diversity involves preserving habitats, creating seed banks, and implementing sustainable land-use practices.

In conclusion, plant diversity is a complex and fascinating field that intertwines with various aspects of life on Earth. Understanding and preserving this diversity is not just an academic pursuit, but a necessity for the continued survival and well-being of our planet.

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An Overview of Plant Diversity

Introduction to plants.

Plants are a highly significant kingdom of organisms. They are multicellular organisms with the incredible capability to produce their food from atmospheric carbon dioxide. If plants were absent, animal life would not survive because they serve as the base of many food webs.

Like the vast Californian sequoias , plants can be as large as 90 metres, or as small as a few millimetres. While Eucalyptus regnans is the tallest angiosperm, Wolffia is the smallest rootless aquatic plant. The most common types of plants on earth are angiosperms or blooming plants. This overview looks at plant diversity based on habitat, stem nature, life span, size and nutrition.

Table of Contents

Introduction to plant diversity, diversity based on habitat, diversity based on habit, angiosperm diversity based on stem nature, diversity based on size, diversity based on life span, diversity based on nutrition.

• Frequently Asked Questions (FAQs)

Kingdom Plantae emerged about 410 million years ago as green algae transitioned from water to land. This land had a rich resource base and was comparatively uncolonised. Additionally, terrestrial habitats provide more light and carbon dioxide, essential for plant growth and survival.

Being multicellular and mostly photosynthetic organisms living both in water and on land, plants can be found almost everywhere. Red, brown, and green algae are among the aquatic plants, and mosses, ferns, gymnosperms, and angiosperms are among the terrestrial plants. Over the past 70 million years, flowering plants known as angiosperms have dominated the planet.

Depending on different characteristics, there are various types of plants. Plants are divided into the following groups according to their habitat (where they reside).

Hydrophytes

The term “hydrophytes” refers to plants that grow in or near water. Such plants have weak vascular tissue, fragile stems, and poor root systems. The majority of the tissue has air spaces and is spongy.

These plants might include the following characteristics:

(i) Submerged (e.g., Hydrilla , Vallisneria , Potamogeton etc.)

(ii) Fixed-floating and free-floating (e.g., Utricularia , Wolffia , Salvinia , Lemna , Ceratophyllum , Pistia , Trapa , Eichornia , etc.)

(iii) Amphibious (partly submerged, e.g., Alisma plantago , Ranunculus aquatilis , Sagittaria , etc.)

Thalassia and Zostera are two angiosperms that are also marine.

Hygrophytes

These plants need moist, dark environments to develop. Their roots and stems have limited growth and are fragile and spongy. The leaves have stomata and are fully developed. Ferns, Aroids, Begonias, and certain grasses are common examples.

These plants can survive in saline water or soil. They can tolerate high salt concentrations (NaCl, MgCl 2 , and MgSO 4 ). They have distinctive breathing roots, or pneumatophores, that are negatively geotropic. Mangrove vegetation like Rhizophora , Ceriops , Avicennia , etc. are common examples.

Mesophytes, which comprise the majority of angiosperms, are those that grow in areas with moderate water availability. They usually develop fast and are large. Their leaves and roots are well developed. The stem could be either woody or herbaceous. Some mesophytes, like deciduous trees, are mesophytic in the summer and xerophytic in the winter.

Xerophytes, such as Acacia , Euphorbia , Amaranthus , Argemone , Nerium , and Ziziphus , are plants that thrive in xeric or dry environments or areas with limited access to water. Some xerophytes are known as succulents because they store water in their stems ( Opuntia ), leaves ( Bryophyllum , Agave ), or roots ( Asparagus ).

Epiphytes are plants that grow on trunks or branches of other plants, such as an orchid or lichen growing as an epiphyte on a mango limb. The epiphytes are regarded as space parasites. An example of commensalism where the host is unaffected is the contact between an orchid (a commensal) and a tree (the host).

Parasitic Plants

These plants, such as Striga and Cuscuta , are parasites that grow on other plants (on roots of jowar).

Angiosperms are divided into four groups based on their form, size, and shape:

Herbs (Herbaceous)

These plants have a short, green, fragile stem. Typically, they have a brief life span, like wheat or gram. Some herbaceous plants have a much reduced underground stem portion, but the aerial branch with flowers at the apex develops from the underground part during reproduction. Such a stem is known as a scape, such as an onion.

Shrubs (Shruby or Fruticose)

These plants are more significantly woody and branching than herbs. They generally have multiple stems but no main axis. Eg., henna, roses, and China roses.

Trees (Arborescent)

The plants are thick, rigid, and woody and are more prolonged or taller than bushes. They have a noticeable trunk.

Nodes and internodes are very apparent in these plants. Most of these plants have hollow internodes. These plants, such as bamboo, are grasses but cannot be classified as herbs, shrubs, or trees.

The angiosperm plants can be categorised as follows based on the type of stem:

These plants develop upright. Due to their strong stems, most trees, shrubs, and some herbs can stand upright on the ground.

These plants have dangling stems that are entirely covered in roots. Leaves originate from nodes, from the culm of which branches emerge. For example, Cynodon , and Oxalis (doob grass). Nodes along the length of the stem produce adventitious roots.

These plants resemble creepers, but adventitious roots do not form at nodes in these plants. A trailer could be procumbent or decumbent. The stem is horizontal in a procumbent trailer (such as Basella ), but in a decumbent trailer, the apex of the stem is lifted above the ground (e.g., Lindenbergia ).

These weak-stemmed plants, such as peas and betels, cling to supports using their adventitious roots, petioles, spines, and tendrils.

The size of the angiospermic plants varies considerably. The rootless aquatic Wolffia is the smallest angiosperm. Its diameter is 0.1 mm. The diameter of aquatic Lemna is 0.1 cm. The Eucalyptus regnans tree is the tallest angiosperm plant. Its height exceeds 100 metres. Some eucalyptus trees grow as tall as 130 metres. The Banyan tree is the largest type of plant ( Ficus bengalensis ). It has more than 200 prop roots and can cover a space of 2 to 5 acres.

Angiosperms are divided into the following four groups based on life span:

Before the arrival of real dry conditions, these plants reach the end of their life span in a very short time. These plants, such as Solanum xanthocarpum , Argemon mexicana , Cassia tora , etc., are not true xerophytes and are often referred to as drought escapers or drought evaders.

After producing seeds, such as those for rice, wheat, and gram, they die within a year of completing their life cycle.

Biannuals (or Biennials)

These plants go through their entire life cycle in two years. They only exhibit vegetative development in the first year, and then, in the second year, they produce flowers, fruits, and seeds. Usually, these plants are herbs, such as carrot, turnip, and radish.

Once established, these plants continue to live for a very long time. More than 200 years old, the giant banyan tree ( Ficus bengalensis ) can be found in Kolkata’s Botanical Garden. At Gaya, there is a Bodhi tree ( Ficus religiosa ) that is roughly 2500 years old.

Most perennials produce flowers and fruits in a specific season of the year after reaching maturity. They are polycarpic, including Acacia , mango, and coconut. Some perennial plants, like bamboo and Agave , are monocarpic, meaning they only produce fruit once during their lifetime. Biennials and annuals are all monocarpic.

Plants are divided into the following categories based on their mode of nutrition:

Autotrophs/ Autophytes

They have the ability to produce their food. They are split into two groups: chemotrophs, which produce their food using chemical energy, and phototrophs (which produce their food through photosynthesis).

Heterotrophs

These plants cannot produce their food and therefore depend on external sources. Heterotrophs can be insectivorous, saprophytic, parasitic, or symbiotic.

Other plant varieties include:

• Polygamous plant (e.g., mango).
• Stolon plant (e.g., Ajuga , Stachys , and Mentha ).
• Seedless vascular plants
• Sucker plant (red raspberry, lilac, and Forsythia ).
• Air layering plants ( Forsythia , jasmine, Hamamelis , Philodendron , etc.).
• Cutting plants.

There are various types of plants, and each one needs a specific environment to develop. The essential elements are sunlight, nutrients, water, air, soil, and temperature, which plants rely on for their life, growth, and development.

Related Links:

• Biodiversity and its Types
• What is Species Diversity?
• Flora And Fauna
• Biodiversity in Plants and Animals
• Plant Kingdom – Members of Kingdom Plantae

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Frequently Asked Questions

What increases plant diversity.

Enhancing crop genetic variety, diverse plantings, rotating crops, agroforestry, and varying the environments around cropland are examples of diversification strategies.

Mention the function of a stem in a plant.

A stem provides the following functions in a plant:

• It supports the fruits, flowers, leaves, and branches.
• It moves minerals and water from the roots of plants to their leaves and other parts.
• It transports nourishment from the plant’s leaves to various plant sections.
• It keeps the plant upright.

Which kind of venation is most likely to be present in a plant with a fibrous root?

Parallel venation is a characteristic of plants with fibrous roots and leaves.

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9.1: Why It Matters- Plant Diversity

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Why differentiate between different types of plants?

Land plants evolved from a group of green algae, perhaps as early as 510 million years ago. The evolution of plants has resulted in widely varying levels of complexity, from the earliest algal mats, to bryophytes, lycopods, and ferns, to the complex gymnosperms and angiosperms of today. While many of the groups which appeared earlier continue to thrive, as exemplified by algal dominance in marine environments, more recently derived groups have also displaced previously ecologically dominant ones (for example, the ascendance of flowering plants over gymnosperms in terrestrial environments).

The establishment of a land-based flora caused increased accumulation of oxygen in the atmosphere, as the plants produced oxygen as a waste product. This rise in oxygen likely contributed to the evolution of life as we now know it.

Plants make our lives possible. Without the glucose they create through photosynthesis, and the oxygen they release into the air, it would be impossible for human life to continue on.

Contributors and Attributions

• Why It Matters: Plant Diversity. Authored by : Shelli Carter and Lumen Learning. Provided by : Lumen Learning. License : CC BY: Attribution
• Modification of Evolutionary history of plants. Provided by : Wikipedia. Located at : https://en.Wikipedia.org/wiki/Evolutionary_history_of_plants . License : CC BY-SA: Attribution-ShareAlike
• Close Thistle. Authored by : etheriel. Provided by : Pixabay. Located at : pixabay.com/en/plant-close-plants-thistle-tapera-1461109/. License : CC0: No Rights Reserved

Chapter 14: Introduction to Diversity of Plants

Plants play an integral role in all aspects of life on the planet, shaping the physical terrain, influencing the climate, and maintaining life as we know it. For millennia, human societies have depended on plants for nutrition and medicinal compounds, and for many industrial by-products, such as timber, paper, dyes, and textiles. Palms provide materials including rattans, oils, and dates. Wheat is grown to feed both human and animal populations. The cotton boll flower is harvested and its fibers transformed into clothing or pulp for paper. The showy opium poppy is valued both as an ornamental flower and as a source of potent opiate compounds.

Current evolutionary thought holds that all plants are monophyletic: that is, descendants of a single common ancestor. The evolutionary transition from water to land imposed severe constraints on the ancestors of contemporary plants. Plants had to evolve strategies to avoid drying out, to disperse reproductive cells in air, for structural support, and to filter sunlight. While seed plants developed adaptations that allowed them to populate even the most arid habitats on Earth, full independence from water did not happen in all plants, and most seedless plants still require a moist environment.

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Biology and the Citizen (2023) Copyright © 2022 by Utah State University is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Plant Diversity Patterns and Drivers

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2.3 Diversity of plants

Biodiversity.

Chapter overview

After looking at the biosphere and where life exists on Earth, we will now look at the biodiversity of life on Earth. This chapter starts off with looking at the classification system and how scientists have classified all living organisms. This hierarchical classification system provides an overview and will be dealt with again in Gr. 10 if learners take Life Sciences. After looking at the five kingdoms, we will then look at the biodiversity of plants and animals. In CAPS, learners would have looked at the variety in plants and animals before in Gr. 5 and heard the term biodiversity. This is built upon and extended as we look at the different classifications of plants and animals. The other three kingdoms, namely Protista, Fungi and Bacteria are not dealt with in detail, but in Gr. 9, learners will again look at some examples when they do microorganisms in more detail.

2.1 Classification of living things (3 hours)

2.2 Diversity of animals (4.5 hours)

2.3 Diversity of plants (3 hours)

• How do we group or classify all the living organisms in the world?
• Why do we need to group or classify living things?
• How can we classify all the animals on Earth?
• What is the difference between reptiles and amphibians?
• Are insects and arachnids (spiders) different?
• Is there a way to classify plants?
• What is the diversity of plants and animals in South Africa?

If possible, display a selection of nature magazines, books and reading materials in the class during the time that you go through this chapter. You can collect photos or pictures from magazines of many different plants and animals, fungi and bacteria. A suggestion is to cover them in plastic, in order to reuse them in subsequent years.

Over millions of years each species living today has changed and adapted to live in a specific type of environment in order to ensure the survival of that species. Biodiversity is a term used to describe the great variety of living organisms on Earth and their varied habitats.

There are just so many types of organisms. How can we make sense of all the organisms on Earth? We need some way to group them. This is called classifying. Let's find out how we do this!

Classification of living things

• characteristic

Grouping has been a common activity in humans for thousands of years as we make sense of the world around us.

Group some everyday objects

In this activity learners will get an opportunity to group a selection of everyday objects according to observable features. This lays the foundation for the classification and grouping work that is covered in this section. Teachers should collect enough shoeboxes or recycled ice-cream tubs (or if this is not possible shopping bags should also work) for each of the groups in the class. As homework the previous day each learner needs to bring five items from home. These items should be small enough to go into the shoebox. They should choose items that they use in their everyday lives. Please ensure that no valuables are brought!

• objects from home
• shoe boxes/ ice-cream tubs

When you observe you use your senses to tell you more about something. How does it feel or look? Does it have a special smell or taste? Is there a specific sound coming from it?

INSTRUCTIONS:

• Work in groups of four.
• Each member of the group should bring five items from home. Choose items that are easy to carry around and that will fit into a standard shoe box.
• Carefully observe each of the items that everyone in your group brought.
• Use the shoe boxes to group the items according to your observations.
• Place all objects brought by the whole class on a display table in the front of the class.

Discuss the different grouping methods that each group has used as a class. Work towards a standard grouping or classifying method that you could use to classify ALL the items that you all brought to school.

During this activity, encourage learners to look at the observable features of the items in order to classify them, for example shape, colour, size, texture, use etc.

Learner-dependent answer.

Write three or four sentences about the standard classification method that you decided to use in your class. What characteristics of the items did you use to classify and group them? Were these different to what you used in your small group?

Aristotle was a Greek philosopher and thinker who lived about 2400 years ago. Aristotle came up with the following grouping system that was used for almost 2000 years after his death!

• He divided all organisms into either animals or plants.
• Then he divided animals into those 'with blood' and those 'without blood'.
• Lastly animals are divided into three groups based on their method of movement: walkers, flyers or swimmers.

Aristotle's classification system

This is an optional activity to introduce different types of classification.

• Look at the following photos of different kinds of animals.
• Use Aristotle's method of classification to group the animals based on the way that they move.
• Draw a table of your groupings in the space provided after the photos. Give your table a heading.

Learner-dependent answer. The table should look as follows. There may be some variations depending if learners decide to put an animal in more than one group or classify it according to its main method of movement.

Classification of a group of animals according to Aristotle's method

Difficult animals to classify are those which can fall into more than one group, such as the penguin, crocodile, human.

Possible answers might include: Some animals fit into more than one group (penguin, crocodile, etc.) because it looks more at what the animals do rather than what they are or similarities and differences between their forms.

As more and more animals, plants and microorganisms were discovered, scientists started questioning Aristotle's classification system. It was not working as well as everyone had believed it would. Why do you think it is important to evaluate how we classify things?

Discuss this as a class. Refer to this process as being a constant refining of the way that classification is done and that it is not a 'given' or a static method. It needs to evolve as our knowledge and understanding of the world and the organisms in it develops and must take these new discoveries into account.

In the 1700s Carl Linnaeus developed the classification system that classified organisms according to their similarities, functions and relationships with other organisms.

Today with the use of modern microscopes and genetics we can classify living organisms very accurately. In this way we are able to classify living organisms according to their shared characteristics.

Scientists estimate that there are up to 30 million species of organisms on Earth! If they use systems to classify these organisms they can see patterns in nature and can see how organisms relate to each other.

Our classification system

All living organisms can be divided into five kingdoms :

What are humans? Which kingdom do we belong to?

Since we know that we are not a fungi or plant, or a protista or bacteria (quite a bit bigger!) we belong to the animal kingdom.

The kingdom Bacteria is often also referred to as Monera .

Think back to the example of how we classify learners at school. First, school is divided into pre-primary school, primary school and high school. If we compare school to the way we classify organisms, we can say that the school system has three kingdoms. But, we need to divide learners up further. So primary school is divided into seven grades (Gr. 1-7) and high school is divided into five grades (Gr. 8-12). The classification system for organisms also needs to divide organisms up further as each kingdom contains thousands of different types of organisms.

Each kingdom is divided into smaller groups or divisions called phyla . Organisms with similar traits (characteristics) will occupy a similar phylum. In each phylum, smaller divisions called classes are found and each class is further divided into orders , families , gen era and then species .

Be careful to use these words correctly: one phylum , many phyla . Similarly, one genus , many genera.

Think of your school again. Your primary school contains many learners. When you divide your entire school into grades, there are fewer learners in each grade. Your grade might be divided into different classes, and each class has fewer learners in it. When we classify organisms, the same thing happens. A kingdom is a very big group, whereas a species is a much smaller group.

Study this diagram to help you remember the order:

A mnemonic takes the first letters of a group of terms to make a funny rhyme.

K ing P hil C uts O pen F ive G reen S nakes

An interactive game on classifying animals http://sciencenetlinks.com/interactives/class.html

We need to be able to distinguish between organisms too. So how do we name organisms?

Binomial comes from the Latin bi - two and nomius - names. Nomenclature comes from Latin words nomen - name and calare- to call. Binomial nomenclature therefore means calling things by two names.

Carl Linnaeus designed a special naming system called the binomial nomenclature to name all organisms. All organisms are therefore given two (bi- means two) words in their name.

• The first part of the name refers to the genus that the organism belongs to. This is always written with a capital letter.
• The second part of the name refers to the species within the genus

If you are typing you will put both these names in italics but if you are doing a handwritten piece you underline it. This shows that you are identifying the organism by its scientific name.

For example, the scientific name for the African elephant is Loxodonta africana . Humans belong to the genus Homo and to the species sapiens so we are Homo sapiens .

The 'scientific name', the 'Latin name' and 'binomial nomenclature' are different ways of saying the same thing. All of these are referring to the same system of naming a species by its genus and species names in Latin.

Have a look at some curious and strange names for organisms http://www.curioustaxonomy.net/index.html

Now that we have seen how to classify organisms, let's take a closer look at the differences between the kingdoms.

Plants and animals

The phylogame (a card game which could be played in class) http://phylogame.org/

Comparing plants and animals

• Study the diagram that shows the five kingdoms that we commonly use to classify organisms. Pay close attention to the plants and animals.
• Answer the following questions.

When we compare plants and animals we can often compare them based on the way that they move, what and how they get food or nourishment, and how they reproduce.

Learner-dependent answers. Might include: all these animals can move using a variety of methods or that all might have a special body covering. These animals all have to eat, either plants or other animals. They generally reproduce by mating with other animals of the same species. Animals drink water. Animals respire as they take in oxygen and give off carbon dioxide, often through breathing. Animals need to excrete their waste from their bodies.

Learner-dependent answers. Might include: plants cannot move, they are rooted to one spot. Plants do not need to eat as they produce their own food by photosynthesis. They take in water. Plants also respire like animals but they also take in carbon dioxide for photosynthesis and give off oxygen as a by product. Plants' reproduction differs to animal reproduction in that many plants produce seeds while others produce other structures (like ferns) etc.

Draw a table in the space below and compare the characteristics of plants that make them different to animals. Discuss your plant and animal comparisons with your group and then with the class.

Learners should compare the observable differences on the diagram / illustration between plants and animals. Some of these might include:

Learn more about the kingdom Animalia

Most people will not eat bread covered in bread mould but will eat a plate of fried mushrooms, truffles and morels. These are all examples of fungi, including yeast.

Morels are a type of edible mushroom. They are distinctive for the appearance of their caps, which are have pits and ridges that resemble a honeycomb.

You can find out lots more online by visiting the links provided in the Visit boxes. Be curious and discover the possibilities!

Fungi play a very important role in our biosphere since they break down dead organic material and return nutrients to the soil for plants to use. Some fungi cause diseases while others, such as penicillin (an antibiotic) are very useful to us. Yeast is used in many of our products, such as making bread rise and fermenting wine and beer.

Protists and Bacteria

Learners will only be able to fully understand the differences between Protists and Bacteria once they have done cells in Gr. 9. Essentially, Protists are eukaryotic (usually unicellular, but not always) as they have cells with a membrane bound nucleus, whereas Bacteria are prokaryotic as their DNA material is not membrane bound. Bacteria are always unicellular. Protists require a liquid medium, whereas Bacteria occur almost everywhere.

We will look at Protists and Bacteria in more detail later on in Gr. 9. For now, lets look at some of the basic features of these kingdoms.

Organisms in these two kingdoms are microscopic which means you cannot see them with your naked eye. However we can see them if we look at them under a microscope.

These images are included to give learners some idea about these two kingdoms, otherwise they will have no reference point until they get to Gr. 8 and do microorganisms again. These images are also interesting and show what is possible with the microscopy techniques available today. They include a range of techniques from scanning electron microscopy, confocal, fluorescent and light microscopy. The differentiation of a membrane bound nucleus in Protists and not in Bacteria is too advanced for learners at this stage if they have not yet done cells. For now, encourage learners to look at the photos, perhaps ask them to explain what they see, and let them get excited about the unseen world! Learners do not need to know how to recognise or name any of these microorganisms.

Different bacteria:

Different Protists:

Now we will look at the amazing diversity of animals and plants on Earth, and especially in South Africa.

Diversity of animals

• invertebrate

Provide learners with old magazines and ask them to cut out any and all animals that they see. (If you teach this lesson a few years running it is worth the effort and money to cut their animals out carefully and have these laminated then they can be used over and over again!) When they have collected a large quantity of animals ask them to group the animals into only two groups. Encourage them to manipulate the animals and transfer them from one group to another, and encourage positive debate about their groupings and why they chose those specific groupings. Then end result should be that there are two main groups of animals, and scientifically speaking these would hopefully be vertebrates and invertebrates, or alternatively those with feathers and those without; those with mammary glands and those without, those with wings and those without, etc. As learners work with the pictures make sure to model words like observe, compare, contrast, evaluate, etc.

Some learners might ask "WHY" we classify and they should be praised for doing this. If this occurs point out to them that classification helps us to sort out ancestor / descendent relationships and we are therefore able to track the evolutionary history of all living organisms.Thus the presence or absence of one specific characteristic might show that an organism is related to others in in a specific genus, family or order and can also guide an investigation into the evolutionary history of these organisms. Many learners might for instance be unaware that lions, rhino and elephants are indigenous to Africa but are also found naturally in other parts of the world, like India, and through classification we are able to see how the Black Buck and the Koedoe, or the One-horned Rhinoceros of Asia and the South African black rhino are related.

Classifying animals

All the animals in the world form part of the animal kingdom.There are two distinct divisions or groups of animals within the animal kingdom: the vertebrates and the invertebrates . Can you remember what is used to classify an animal as a vertebrate or invertebrate? Look at these x-rays of animals for a clue.

The presence or absence of a backbone is used to classify animals as vertebrates or invertebrates. The dolphin, dog and goose are vertebrates and the grasshopper and crab are invertebrates.

Almost 98% of all the animals that have been discovered on Earth are invertebrates!

Animals that have a backbone with a hollow tube inside to hold the nerves are vertebrates. As we can see in the x-ray images of the dolphin, dog and goose, we can see the skeletons of these vertebrates. They are made of bone. We say that vertebrates have an endoskeleton.

What about the grasshopper and the crab? Why can we not see their bones? This is because invertebratesdo not have a skeleton made of bones. The grasshopper and crab have a hard shell covering on the outside of their bodies. This supports their soft bodies inside. We say they have an exoskeleton. But not all invertebrates have an exoskeleton.

What about a jellyfish? It does not have a backbone, so it is not a vertebrate, so it must be an invertebrate. Does it have a hard, outer covering called an exoskeleton? Discuss this with your class. Make sure to take note of the third type of skeleton in your discussion.

Invertebrates do not have a backbone, but this does not necessarily mean that they have an exoskeleton. Many invertebrates have a hydrostatic skeleton , like the jellyfish and earthworm. Some invertebrates such as like the snail and have an exoskeleton (shell) and a hydrostatic skeleton. Sponges actually have a type of endoskeleton as their 'skeletons' are made of calcareous spicules.

Classifying vertebrates and invertebrates

In the table identify the type of skeleton that each animal has and write it down beneath each picture.

Write down whether the animal is an invertebrate or a vertebrate.

A useful chart showing the classification system http://www.usefulcharts.com/science/classification-of-animals-chart.html

'Phylum' is the singular and 'phyla' is the plural use of the word.

The invertebrates are divided into five phyla. The invertebrate phyla are:

• Sea sponges

The five phyla making up the invertebrates have scientific names, but these are not necessary to know at this stage. We will only focus on the two phyla Arthropoda and Mollusca.

Vertebrates belong to the phylum Chordata. Vertebrates are subdivided into five classes.

Only about 2% of all the animals on Earth have a backbone.

Have a look at the following diagram which shows the different classes of vertebrates and phyla of invertebrates. Remember, all vertebrates belong to the phylum Chordata.

Identify the five classes of vertebrates

• Study the previous chart showing vertebrates and invertebrates and identify the names of the five classes of vertebrates. Write these on the lines below.
• Use the pictures that you previously collected from magazines to find at least 5 examples of each of these classes of animals.

Identify at least one distinguishing characteristic that each class shares or has in common (that makes that class different from other classes.) Write this on the line next to the classes that you identified above.

• Fish - scales / gills / fins / etc
• Amphibians - soft moist skin / lungs and skin used for breathing / four limbs with webbed feet
• Reptiles - scaly skin / lungs used for breathing / four limbs with toes
• Birds - beak, feathers cover body / air sacs used for breathing / two scaly legs and two wings,
• Mammals - fur or hairy skin / lungs / four limbs / mammary glands, live birth

Since many animals in Africa are under threat due to habitat loss and poaching the animals featured in this section were specifically included to raise awareness and to expose learners to the wonderful animals living in South Africa. Teachers are encouraged to work with teachers from other subjects, such as the languages or art, to let learners make anti-poaching or awareness campaign posters to address the environmental issues and raise awareness with other learners in the school.

Vertebrates

• ectothermic
• endothermic
• larva / larvae
• mammary gland

The five classes of vertebrates are:

Visit http://school-of-fish.co.uk/teacher_resources_topic.php for a teachers' support website on fish.

Fish come in all sorts of shapes, sizes and colours. There is huge diversity amongst fish. Have a look at some of the following drawings of different types of fish.

Unusual and weird deep sea fish (video)

Identify defining features of fish

Features learners might list include: ectothermic, backbone, fins, gills, scales, living in water, breathing oxygen from water, streamlined body, lay eggs.

The combination of gills, fins and the fact that fish live only in the water are the main defining characteristics of fish and make fish different from all other animals.

When classifying fish we look closely at the material that makes up the skeleton of the fish. This leads us to divide fish into two main groups:

Cartilaginous fish have skeletons made of cartilage .

Bony fish that have skeletons made of bone.

An ancient fish-like class of animals are called Agnatha. Hagfish and Lampreys are part of this group. Hagfish for instance look more like worms than fish. There is controversy over whether hagfish should be classified as fish or not.

Interesting article on the use of hagfish slime to make clothing! http://www.bbc.co.uk/news/magazine-21954779

Sharks, skates and rays are part of a group of cartilaginous fish because their skeletons are made of cartilage. These fish breathe using five to seven pairs of gills .

Two thirds of the sharks brain is dedicated to its sense of smell. A shark's sense of smell is so well developed that it can tell the direction from which a smell is coming.

A whale shark is a shark and not a whale. It is the world's largest fish and it eats only plankton.

The coelacanth was thought to be extinct for 65 million years, but was discovered in a catch of fish in 1938. Since then, more have been found along the coast of Southern Africa.

The largest group of all vertebrates are bony fish. Bony fish have a hard, bony skeleton.

Challenge question: Is a seahorse a fish? Search books and the internet to find out and explain why we can or cannot consider it to be a fish.

Yes a sea horse is in fact a fish. It breathes with gills, has a swim bladder to control buoyancy and a spine, and even though they don't have a tail fin they have four other fins that help them move. Unlike most fish, sea horses do not have scales, but skin.

The male seahorse actually becomes pregnant! The female squirts her eggs into the male's pouch and he then fertilizes them and incubates them until they are ready to hatch.

Watch this video of a male seahorse giving birth

Did you know that the word amphibia comes from two Greek words, amphi meaning both and bios meaning life? So an amphibian is an animal that has 'both lives'. What does this mean?

Amphibians are animals that include salamanders, newts, caecilians, frogs and toads. Let's find out what is meant by amphibians having 'both lives'.

A group of birds is called a flock, a group of cattle is called a herd, a group of lions is called a pride, but a group of frogs is called an army.

Describing amphibians

• Study the photos of different amphibians in the following table.
• Answer the questions which follow.

Salamanders can regenerate (regrow) their limbs and tail within a few weeks if they were lost due to predator attacks.

The young larvae are all in water whereas the adults are on land or near water.

What do you think the larvae need to breathe underwater? What do the adult amphibians need to breathe when they are on land?

The larvae needs gills to breathe in water, the adults have lungs to breathe on land.

Amphibians have two stages in their life cycle. First, they have the larval stage where they are in water, and then they have the adult stage where they live on land (and also in or near water).

Amphibians are ectothermic . Explain how an amphibian keeps its body warm.

They get heat from their environment and therefore need to live in areas where it is warm enough for them to have enough body heat to survive. If it gets very cold an amphibian will need to either find a space under a log or leaves, or else sit in the sun.

Learners need to compile a plausible explanation or hypothesis. The correct explanation is: Glands in the skin secrete liquid to keep the skin slimy and moist as frogs may need to use the skin alongside the lungs and mouth for gaseous exchange.

Look at the following image of a caecilian. There is a debate going on in a Gr. 6 class. Some learners think this animal is a worm, making it an invertebrate. Others think it is a snake, making it a vertebrate. What do you think?

The caecilian is actually an amphibian! What characteristics would you test or make sure this animal displayed to explain to the Gr. 6 learners that it is not a worm. Secondly, what would you need to find out and explain to the learners to explain that it is not a reptile (a snake) but an amphibian?

In order not to be an invertebrate, like a worm, the animal needs to have a backbone. The caecilian does have a backbone and a skull. The caecilian is not a snake (it is not a reptile) as it has a larval stage which is born in water and it undergoes metamorphosis to become the adult caecilian. The larvae also have gills to breathe underwater. Caecilians also do not have scales like reptiles.

Amphibians lay their eggs in water, like this frog. Why do you think they need to do this? Give two reasons.

Some possible reasons are: The eggs are in water so that when the larvae hatch they are already in the water to swim around, the eggs would dry out if they were not in water, the fertilisation process in amphibians often requires water as the female will lay the eggs and as she does so, the male deposits his sperm is the water around them so they are fertilised.

You can tell the difference between frog eggs and toad eggs because frogs lay their eggs in clumps and toads lay their eggs in strings. Have you ever seen frog or toad eggs?

Interesting article on caecilians http://www.sciencenewsforkids.org/2012/05/caecilians-the-other-amphibian/

Metamorphosis: Amphibians (full documentary).

Reptiles have survived on Earth for millions of years. The first reptiles on earth lived 310 to 320 million years ago and included the dinosaurs.

Learn about a fascinating reptile found in Australia called the thorny dragon http://www.wild-facts.com/tag/thorny-dragon/

Most reptiles live on land although some, like crocodiles, terrapins and turtles, and some snakes and lizards spend large portions of their lives in water. Reptiles are ectothermic. They cannot regulate their body heat but depend on their environment for heat.

Reptiles are covered in dry scales. Reptiles reproduce by laying their eggs on dry land. The eggs are covered by a leathery or hard shell.

Learn more about the boa constrictor which keeps its eggs inside its body until they are ready to hatch http://www.theanimalspot.com/boaconstrictor.htm

Reflect on reptiles

• Since reptiles all have a backbone they are one of the classes of ______.
• Reptiles are ectothermic which means that ______.
• chordata or vertebrates
• they cannot regulate their body temperature but depend on their environment for heat

Make a biological drawing with labels and a heading of the lizard lying in the sun in the previous photo.

Learner-dependent answer

We can divide reptiles into four main groups. Each of the photos in the table below shows an example of a reptile from each of these groups. Try to identify the four groups based on the animal in the photo.

Turtles are only found in the sea, terrapins are found in freshwater, and tortoises do not swim around, but walk on land.

If possible, take your learners outside before you start discussing birds to see if you can spot any in the school grounds. Ask learners to identify what is common among all the birds - they should note that all birds have feathers. This is the most distinguishing feature of birds.

Identify characteristics of birds

• Work in groups of three.
• List the identifying characteristics of birds following these steps:
• Do you remember learning about birds in previous years? Work with a different group and brainstorm identifying characteristics of birds. Study the photo of the blue crane above for some clues.
• Use one specific colour to list the characteristics that your group can think of.
• As you learn more about characteristics of birds add these in a different colour to help you remember the new characteristics.

Learner-dependent answers. You should once again ask groups to share their characteristics with the class in order to avoid incorrect characteristics from being included. A typical incorrect characteristic might be that all birds can fly. Point out that many birds, such as penguins and ostriches, cannot fly and remind them that Aristotle used this same classifying technique which proved to be of little use. There are also other animals that can fly which are not birds, such as bats and flies. Learners should note that all birds have beaks, wings and feathers and they lay eggs.

All vertebrates have a backbone with a hollow tube running inside it carrying the nerves.

Just like mammals, birds are also endothermic . What does this tell us about their bodies?

This means that birds can control or regulate their body temperature and can therefore keep warm in very cold climates and keep cool in very hot temperatures.

Learner-dependent answer. Note: Although almost all learners will say that all birds have feathers, not many will be able to identify that birds' feet are covered in scales like those on reptiles. If you are able to go outside to look at some birds, try to see if you can take note of their legs and feet.

Learners are required to evaluate a statement and give an explanation for their evaluation. It is in fact incorrect to say that birds have wings to fly since not all birds' wings are used for flying and many flightless birds exist. Think of the emu, ostrich, penguin, cassowary, kiwi and rhea. A better statement would be: Birds that can fly have wings to do so.

Study the pictures of these flightless birds and compare them with the flying birds in the next column. Use the pictures to write a paragraph explaining the observable differences between flightless and flying birds and why you think these characteristics help some to fly and others not.

The ostrich is very big and has a heavy body with long legs. Its long legs help it to run fast on land. It has wings, but its wings are small in comparison to its big heavy body. The albatross is also a big bird but it has a very large wing span relative to its body. The feathers in the albatross are also small and lie close together to help the bird to fly. Whereas the ostrich has many feathers, but they are big and loose and will not catch the updraft of the wind. The penguin also has a body shape which is not designed to help it fly, but rather to swim. It has short, stubby wings, which are not strong enough to lift it off the ground, but are useful for swimming. It is quite fat and heavy, but this helps to keep it warm in the water. The hummingbird is very light and has small wings which beat extremely fast, allowing it to fly and hover. The hummingbird has wings designed to flap quickly in the wind as they are narrow and light, while the penguin has fatter wings shaped like a paddle which are rather used for swimming.

An application for a smart phone which helps you to identify all birds in South Africa. http://www.sasolbirds.co.za/mobile-app.php

Identify characteristics of mammals

• Work in groups of three to four.
• You might have learnt about mammals in previous years. Work with your group to brainstorm as many identifying characteristics of mammals that you can think of. Study the diagram of the lion above for some clues.

List the characteristics that you can identify in the space below using one specific colour.

As you learn more about mammals, add what you have learnt to this list in a different colour. This will then provide a summary on mammals when you have completed the section.

Learner-dependent answers. Note: After learners have generated their lists, you should ask groups to share their characteristics with the rest of the class in order to insure that no false characteristics are included (although these would provide a foundation for discussion as to why they are not identifying characteristics for instance). Some characteristics that learners might identify are: warm-blooded (endothermic), four limbs, sexual reproduction, live young, hair on bodies.

Mammals are vertebrates meaning they have a backbone. Almost all mammals are endothermic. This means they are also able to maintain (keep) their body temperature at a constant level.

The Naked Mole Rat has lost the ability to regulate its body temperature while other mole rats have weakened abilities to do this since they live underground in areas where the temperatures are generally very stable.

'Thermic' means to do with temperature and 'endo' means inside, so mammals are endothermic as they can regulate their body temperature from the inside.

Mammals give birth to live young which are fed milk. The milk is produced by the mother's mammary glands (in the teats or breasts). Mammals also have hair on their bodies. This varies greatly between mammals. Mammals also have teeth that look different in different parts of the mouth.

All mammals breathe using lungs. Many mammals therefore live on land. Those mammals that do live in water, like whales and dolphins, have to come to the surface of the water to breathe.

Whales and dolphins are born with a layer of hair that gradually thins out as they grow older and eventually disappears. Why do you think they lose their hair?

While the larger cats (lion and leopard) prefer to hunt at night to avoid overheating, cheetah hunt in the middle of the day. There is then less chance of them losing their catch to the larger cats.

Why are there no giant mammals? (video)

Now that we have studied the five main classes of vertebrates it is easy to compare them!

Comparing vertebrates

Use the table below to compare the vertebrates shown in the photos based on the features in the first column.

Now that we have looked at all the classes of vertebrates, let's have a look at the invertebrates.

Invertebrates

• exoskeleton
• jointed (segmented) limbs

What should you look out for when you have to decide if an animal is an invertebrate?

• All invertebrates lack a backbone. They either have a hard outer shell or a fluid-filled structure that acts as a skeleton (for example jellyfish and slugs).
• All invertebrates are ectothermic.

Did you know that 97% of the animals on Earth are invertebrates? Due to the huge diversity in the invertebrates, it can sometimes make classifying them a bit tricky. The invertebrates are divided into several phyla. Some of the invertebrate phyla are:

• Molluscs (for example snails and octopuses)
• Arthropods (for example insects, spiders and crabs)
• Echinoderms (for example sea urchins and starfish)
• Cnidaria (for example jellyfish)
• Porifera (sponges)
• Annelids (segmented worms)
• Platyhelminthes (flatworms)

There are some other phyla too. As you can see, the invertebrates are a very large and diverse group of animals. We are mostly going to focus on the two phyla Arthropods and Molluscs.

Find out more about the other phyla of invertebrates http://www.earthlife.net/inverts/an-phyla.html

The word arthropod comes from two greek words arthron meaning 'joint' and podos meaning 'leg', so together it means 'jointed legs'. Arthropods have an exoskeleton and they have jointed (segmented) limbs.

Let's now find out more about Arthropods!

The invertebrates that fall into the phylum arthropoda, all have a hard outer covering called an exoskeleton . The exoskeleton protects the animal and provides a place for its muscles to attach and function.

Classifying arthropods

If possible, collect different arthropods in a terrarium and have learners study them with magnifying glasses as they work through the activity. However, photos have been provided if this is not possible. Learners can still be encouraged to study different arthropods in the school premises as they work through the activities. If the school permits this, ask learners to walk around school taking photos with cell phones or cameras of arthropods to share with the class. If the school has access to an interactive whiteboard, put these photos up and use these to complete this activity.

• Study the photos of different arthropods below.
• Answer the question that follow.

The mosquito is responsible for more human deaths each year than any other animal on earth! Malaria is carried by mosquitoes and passed to humans when an infected female bites.

Centipedes are venomous and have a very painful sting!

Describe how the bodies of the different arthropods look and if you could touch it, what do you think it would feel like?

Do you think their bodies would be warm or cold?

• They have hard shell-like bodies that look sturdy and inflexible; it would possibly feel hard and would crunch if broken.
• Their bodies would feel similar to the temperature of their environment.

One way to classify an arthropod is to count its legs and to group these animals according to this. Count the legs on each of these arthropods and write their names in the appropriate column below to see to which group they belong.

• The legs are made of different parts that are joined together and are mostly covered in the same hard exoskeleton as the body.
• Where the pieces of the leg come together they form a flexible joint that allows the leg to bend and move.

The learners' tables must look like this:

It sheds the hard exoskeleton (outer skeleton) in a process called moulting .

Most crustaceans are aquatic, either marine or freshwater. The other classes mostly live on land, although many live near water.

Insects have wings. No, not all insects have wings.

The coconut crab ( Birgus Latro ) is the largest land-living arthropod on Earth and weighs up to 4 kg! It can crack whole coconuts with its pincers.

Molluscs are a very diverse phylum of invertebrates. They have a huge range in body shapes and sizes. Molluscs are often given a general description which is that they have internal or external shells and a single muscular 'foot'. However, there are lots of molluscs which do not strictly fit this description, such as slugs.

Mollusc is Latin for "soft" which refers to the soft bodies of molluscs.

The group of molluscs include snails, squid, octopuses, periwinkles, abalone, mussels, oysters and other soft-bodied animals.

Video on nudibranch sea slugs

Video on Cuttlefish: The chameleons of the sea

Observing molluscs

• Carefully study the above photos of different animals that form part of the phylum mollusca.

Molluscs have soft bodies, which are often slimy to touch. Most molluscs have one or two hard shells to protect their bodies, sometimes the shell is inside, like that of the cuttlefish, squid and octopus. Molluscs live in moist environments, mostly in the sea.

They would dry out and die.

Learner-dependent answers - they might say that they found more snails in low-traffic areas and in shady, less-exposed places, often where it is damp or under foliage.

If possible, collect a few snails to study in class. If you have a glass terrarium or an old aquarium, keep the snails in there, or else keep a few in large clean glass jars.

Note: In the last section of this term's work learners are going to study variation and survival of the strongest / fittest. They will need snails for that activity too, so if possible keep the snails from this activity for then. Just make sure the lid is securely shut on the terrarium as snails will escape and arriving to a slime-covered desk / class before school is no fun at all!

Carefully study their bodies and especially their long, slimy foot.

What do you think the slime is used for?

Describe how the snail moves.

How many tentacles ( antennae ) does the snail have? What do you think these are used for?

What markings are on the shell? Why do you think the shell is marked in this particular way?

Try and see if you can find male and female snails. What conclusion can you draw from this.

• As the snail moves it leaves behind a trail of slime to make it easier for the rest of the body to slide or glide over. This allows it to move easily over any type of surface.
• Muscles in the foot of the snail contract and relax causing it to move along.
• Snails can have one or two pairs of tentacles (antennae) depending on the species (however they may be retracted). One pair of light-sensitive eyes are usually on the longest pair of antennae and the other pair of antennae are used for smell and touch.
• The snails' shells are marked to blend into their environment and to break the outline of their shape to help to camouflage them.
• Learners should say that they cannot see any difference and should be able to conclude that either they only collected one sex or that snails do not have a male and a female snail (which is in fact the truth). Most land snails have both male and female parts. They are hermaphrodites. When they meet with other snails during mating they will both conceive and lay eggs, so double the number of offspring are formed.

Make a drawing of a snail. Include the following labels: hard shell, foot, head, mouth, tentacle, eyespot.

Diversity of plants

In this section we will take a closer look at the organisms in the plant kingdom . So how do we classify plants?

This section guides learners as they investigate the plant kingdom by grouping plants with seeds and those without seeds into two main groups.

Classifying plants

As an introduction to the diversity of plants, you can do a short walk around your school, aimed at developing a greater awareness of the plants in and around the school, and specifically those that produce seeds and those that do not. Also encourage learners to take note of leaf shape, size, flowers, etc.

We can easily compare plants based on their characteristics. For example, their leaf size and shape, whether there are flowers or not and how the petals look, the length and depth of the roots and the type of root system, and many others.

If you would like to join and become a research scientist yourself, visit the iSpot website http://www.ispot.org.za/

One particularly useful way is grouping plants according to how they reproduce sexually. If we group plants based on the way that they sexually reproduce we can quickly see two distinct groups:

Plants with seeds

• Seedless plants

Plants can also reproduce asexually by making a clone or copy of themselves. In this way new plants can grow from cuttings and tubers (like potatoes), from bulbs and rhizomes , or from shoots and side branches.

Plants that do not produce seeds include ferns, mosses and algae. These plants produce spores . The spores often develop in structures found on the underside of the leaves or fronds. The spores grow into new plants.

If possible, pick some fern fronds to bring to school. You can also look for moss growing in moist environments, such as under a dripping tap and pick some to bring to class. You can then show learners the spore forming structures on the underside of the fern leaves.

Ferns have been around for about 400 million years. That is even older than dinosaurs, and they are still living on Earth today.

The following photo shows a close-up of the underside of a fern leaf. Can you see the clusters of capsule-shaped structures that form the tiny spores?

A small hand lens is useful to examine the underside of the fern leaves (if available).

The close-up photo on the right shows a moss sporophyte. This contains the spores of the moss plant.

Do you know what lichen is? You often see it growing on rocks and tree trunks. Do you think lichen is a plant? Look at the photos of lichen below.

Lichen actually consist of two different organisms growing together! A fungus and a green alga grow together in a symbiotic relationship. The fungus absorbs water from the environment and provides the algae with an environment to grow in. The green algae photosynthesizes, providing food for the itself and the fungus. Why can the fungus not make its own food? Is the fungus a plant? Can you come up with a definition for a symbiotic relationship? Discuss this with your class and take some notes.

Alga is singular and algae is plural!

Discuss this with your learners. Encourage them to take notes in the margins of their workbooks. A fungus is not a plant. Fungi are one of the five kingdoms of organisms. Fungi do not contain chlorophyll and cannot photosynthesize. They therefore need to obtain their nutrients from elsewhere. Ask your learners what they think a symbiotic relationship is. A symbiotic relationship is one in which one or both organisms benefit. A parasite is something which lives off another organism in some way and harms that organism. The relationship benefits the parasite, but not the host. It is not mutually beneficial. On the other hand, the honey bird and the badger, which learners may have learned about in Gr 6, both benefit from their relationship. It is a mutually beneficial symbiotic relationship. Start by asking learners if the relationship between the fungus and the alga is beneficial to one or both of them? Both the algae and fungus benefit from the relationship. Therefore it is a mutually beneficial symbiotic relationship.

The other group of plants produces seeds. These plants can either produce seeds in flowers or they can produce seeds in cones. Most plants that you see around you, produce seeds. Plants that produce seeds in flowers are called angiosperms and plants that produce seeds in cones are called gymnosperms .

We can therefore classify plants as follows:

Come back to complete this diagram once we have learned more about angiosperms.

The words to fill in on the diagram are monocotyledon for one cotyledon and dicotyledon for two cotyledons.

Seed-bearing plants

• dicotyledon
• monocotyledon

Gymnosperms

Have you ever seen a living prehistoric plant? If you thought about it, you probably have without even realising it!

In South Africa we have plants called cycads that are often referred to as 'living fossils'. Cycads grew in great numbers during the Jurassic period. They have not been around for as long as ferns and algae, but they have been on Earth for longer than all flowering plants. Flowering plants (angiosperms) evolved after gymnosperms.

South Africa is considered a diversity hotspot for cycads. Along with Australia, Mexico, China and Vietnam, we account for 70% of Earth's cycad species.

http://www.plantapalm.com/vce/toc.htm for more information on cycads.

Can you see the large cones in the photo of the cycad above? They are in the centre of the plant. The cones are made up of many individual seeds. Look at the following close up images of cones.

The word gymnosperm means 'naked seed'. Gymnosperms are considered to have naked seeds as the seeds are not covered in a fruit, like we will see in angiosperm plants.

Another gymnosperm which is native to South Africa, and grown a lot in the Cape is the Mountain Cypress, as shown in the photo. They grow especially well at high altitudes, such as in the Cederberg Mountains.

There are several species of gymnosperms which are not indigenous to South Africa. What does this mean? Let's find out.

Invasive plants in South Africa

• Study the following photographs of various gymnosperm plants in South Africa.
• Answer the questions that follow.
• You will need to do some research in books and on the internet.

QUESTIONS :

An indigenous plant is one which occurs naturally in a particular geographical such as South Africa.

An alien species is one which is not indigenous to South Africa, or a particular geographical area. It has been brought in by humans from another part of the world. They are said to be invasive as they invade (take over) the areas in which indigenous plants grow.

They are gymnosperms so they reproduce by making seeds in cones.

Learner-dependent answer. Learners may either disagree or agree. There are many viewpoints on this at the moment. Perhaps they feel that this is one area which mountain bikers should be allowed to enjoy as a forest as the rest of Table Mountain is covered in fynbos. Alternatively, they may agree that we need to re-establish the local flora and fauna, and although it may take time for a forest and shade to regrow, it will be better in the long run from an ecological point of view.

Pretoria's Jacaranda trees are an 'alien' problem. (video)

Let's now take a look at the other group of seed-producing plants, angiosperms.

Angiosperms

Angiosperms are flowering plants. They produce flowers which develop into seeds that can grow into new flowering plants. We will learn more about reproduction in angiosperms in the next chapter. Most of the plants that you probably see around you in the gardens are flowering plants.

An idea to introduce this topic is to get sheets of paper and get learners to brainstorm the names of as many flowering plants as possible that they know. As many learners are not that familiar with the names of plants and animals in their area, we encourage teachers to use this to add names of plants as learners get to know them in this section. Encourage learners to review the chart they make and to add to it as they go along. Try and identify as many local examples as possible with your class. This is aimed at showing the diversity of flowering plants in South Africa. You can even cut some flowers to bring in to class.

We can group flowering plants into two major groups:

monocotyledons

dicotyledons

All the angiosperm plants that we are studying have the following characteristics in common:

A huge thorn tree does not look anything like a maize plant, yet they are both flowering plants. They both have roots, stems , leaves and their flowers produce seeds. So why can we group the one as a dicotyledon and the other as a monocotyledon? Let's find out!

If possible, bring some examples of monocots and dicots into class for this activity so that learners can study actual examples of the plants. Be sure to include some wind pollinated plants that do not have obvious flowers, as many learners don't realize that grasses form flowers.

Discovering the differences between monocotyledons and dicotyledons

• Study the photos of South African monocotyledons and then dicotyledons.
• Answer the questions which follow about each group.

Monocotyledons:

Learner-dependent answer. The leaves are generally long and narrow. The veins run parallel down the length of the leaves.

Describe the stems. Are they woody stems or green ( herbaceous ) stems?

The stems are all green, with no wood. They are herbaceous.

Look at the following photos of typical monocotyledonous flowers. Count how many petals are on each flower. What can you generalize about the number of petals (and other flower parts) in monocotyledonous flowers?

The amaryllis flower has six petals, the agapanthus flowers also have six petals, the disa has three petals. We can say that in general, monocotyledonous flowers have parts in multiples of three.

Many of the crops that we grow are monocotyledons, such as maize and sugar cane. Name two others.

Some examples include: wheat, rice, oats, barley, sorghum.

Dicotyledons:

The leaves are varied in shape and size. They are generally broad and the veins form a branching network across the leaves.

The stems are varied, some are green and some are woody, for example in the tree species.

Look at the following photos of typical dicotyledonous flowers. Count how many petals are on each flower. What can you generalize about the number of petals (and other flower parts) in dicotyledonous flowers?

The geranium flowers have ten petals, the plumbago flowers have five petals, the hibiscus flower has five petals, the hydrangea flowers have four petals. We can say the dicotyledons have flowers with parts in multiples of four or five.

Look at the following image which shows the difference between monocotyledonous seeds and dicotyledonous seeds. Monocotyledons have one cotyledon and dicotyledons have two cotyledons.

Learners may be under the impression that the entire mielie pip is the cotyledon.You may want to explain that the little "yellow bit" that can be squeezed out of a maize pip is the cotyledon of the embryonic plant. The rest is just stored food.

Using the information you have discovered in this activity, complete the following table to summarize the differences between monocotyledons and dicotyledons.

Hydrangea flowers can tell us about the soil acidity! An acidic soil (pH below 7) will normally produce blue flowers, whereas an alkaline soil (pH above 7) will produce more pink flowers.

The biodiversity of South Africa's fynbos. (video)

Find out which of South Africa's plants are most threatened and closest to extinction http://redlist.sanbi.org/

• All the plants, animals and microorganisms and their habitats make up the total biodiversity of planet Earth.
• Living organisms are sorted and classified according to their shared characteristics.
• Many scientists have developed different systems to group and classify the living organisms on earth.
• We use a classification system that groups living organisms into five main groups or kingdoms: Bacteria, Protists, Fungi, Plants and Animals
• All living organisms have to perform the seven life processes and the way in which they perform these help us to classify them into different groups, putting plants into one group and animals into another for instance.
• We can divide a kingdom into smaller and smaller groups, in this order: phyla, classes, orders, families, genera and species.
• In the kingdom of animals, we can get two main groups of animals - this with a backbone called vertebrates, and those without a backbone called invertebrates.
• The vertebrates are divided into five groups: Mammals, Birds, Reptiles, Fish and Amphibians.
• The invertebrates make up the largest group of animals and there are many thousands of species. We also divide the invertebrates into different groups or phyla like the arthropods, molluscs, sponges and jellyfish, and many others.
• Arthropods all have a hard exoskeleton and jointed legs, such as insects, arachnids (spiders) and crustaceans (crabs).
• Molluscs have a soft body with or without a shell, such as snails and octopuses.
• In the kingdom of plants we also get two main groups: plants that produce seeds and plants that do not produce seeds but spores.
• Seedless plants produce spores - like ferns and some mosses.
• Seed producing plants can be further divided into angiosperms (seeds in fruit) and gymnosperms (seeds in cones).
• Angiosperms can be further divided into monocotyledons and dicotyledons.
• Monocotyledons have seeds that only have one part or cotyledon. Their stems are herbaceous. The leaves are simple, long and narrow and their flower parts are arranged in multiples of three.

Dicotyledons have seeds with two parts or cotyledons from which their tap root grows deep into the soil. Their stems can be woody or herbaceous. The leaves are varied in shape and size and have a network of leaf veins . Flower parts are usually arranged in multiples of four or five.

Concept map

This concept map shows how the concepts in this chapter on Biodiversity link together. Complete the concept map by filling in the five Kingdoms that living things are classified into, and also giving the two major groups of angiosperm plants.

Can you see how the arrows show the direction in which you must "read" the concept map?

Teacher's version: Remember that concept maps are different to mind maps in that concept maps have a hierarchical structure and show how concepts link together using arrows and linking words. Whereas mindmaps generally contain a central topic and individual branches coming out which do not necessarily link together. Mindmaps can also be a useful way of summarizing information and studying, however, we are using concept maps as they help to show linkages, which is very important in science. Help your learners to "read" the concept map by showing them that the arrows show the direction in which concepts progress and are linked to each other.

Revision Questions

Use the following diagram to fill in how we classify organisms. The first 3 have been filled in as we did not discuss domains in this chapter. You will learn more about domains in later grades. [6 marks]

Which two levels of classification do we use to name an organism. What is the correct way to write the scientific name of an organism? [3 marks]

We use the Genus and Species name. The correct name is the Genus must have a capital letter and the species a small letter and it is in italics if typed or underlined if handwritten.

As more animals were being discovered it became obvious that many animals can fall into all of these classes and thus it was not a very accurate method of classification.

Use the following space to draw a classification diagram of the animal kingdom. It has been started for you. You only need to include the phyla and classes that we studied in detail. [11 marks]

The following gives an example of the animal classification learners could have drawn.

The existence of a large number of different kinds of plant and animal species which make a balanced environment. [1 mark]

• biodiversity
• vertebrates and invertebrates
• fish, amphibia, reptiles, mammals, birds
• False - A large percentage of living organisms are invertebrates; OR A small percentage of the living organisms are vertebrates.
• False - Molluscs typically have a hydroskeleton and only some have shells.
• False - Birds have feathers but also have leathery scales covering their legs. (A body covering encompasses the entire body of the animal.)
• False - An advantage of being endothermic is that the animal is able to move when it is very cold unlike cold-ectothermic animals.

Look at the following sentences and underline the one that best describes mammals. [1 mark]

• Mammals are animals that breathe, move, eat, reproduce and excrete.
• Mammals are animals that can regulate their body temperatures.
• Mammals are warm blooded animals that feed their young, have special organs for breathing and a backbone.
• Mammals are warm blooded animals with mammary glands, a hairy body, lungs and a backbone.
• Mammals give birth to live young, can be found living on land and in water, and can sense their environment with well defined smell and touch senses.
• Too broad - all animals should be able to fulfil these if they are alive.
• Too vague - birds and mammals can regulate their body temperatures.
• Too vague - this can easily describe birds as well.
• Learners should underline d.
• Could describe a boa constrictor as well.

Describe how the seeds of angiosperms differ from those produced by the organism in the photo. [2 marks]

Seeds in angiosperms are enclosed in fruit; seeds of gymnosperms are 'naked' or on the cone itself.

Learners could produce something like the following.

Total [55 marks]

short essay on diversity in plants

250 Words Essay on Diversity in Plants Introduction. Diversity in plants, also known as phytodiversity, is a fascinating field of study, encompassing the broad spectrum of plant species and their unique characteristics. It plays a pivotal role in the planet's ecological balance, influencing everything from climate regulation to food chain ...

Parasitic Plants. These plants, such as Striga and Cuscuta, are parasites that grow on other plants (on roots of jowar). Diversity Based on Habit. Angiosperms are divided into four groups based on their form, size, and shape: Herbs (Herbaceous) These plants have a short, green, fragile stem. Typically, they have a brief life span, like wheat or ...

Biodiversity of plants ensures a resource for new food crops and medicines. Plant life balances ecosystems, protects watersheds, mitigates erosion, moderates climate, and provides shelter for many animal species. Threats to plant diversity, however, come from many angles. The explosion of the human population, especially in tropical countries ...

Land plants evolved from a group of green algae, perhaps as early as 510 million years ago. The evolution of plants has resulted in widely varying levels of complexity, from the earliest algal mats, to bryophytes, lycopods, and ferns, to the complex gymnosperms and angiosperms of today. While many of the groups which appeared earlier continue ...

In such a context, the Special Issue " Ecology, Evolution and Diversity of Plants " has been launched to explore plant diversity from ecological and evolutionary viewpoints. Thus, the published articles have focused on broad key topics in plant diversity, from species to populations and vegetation; as well as from past to current taxa [ 4 ...

When plants developed basic tissues and organs and thus became mature enough to survive on land, they started to increase in their diversity. All plants studied in this and following chapters belong to plants 2 2, or kingdom Vegetabilia which is split into three phyla (Figure 6.1.1): Bryophyta (mosses and relatives), Pteridophyta (ferns and ...

Chapter 14: Introduction to Diversity of Plants Figure 14.1 Plants dominate the landscape and play an integral role in human societies. (a) Palm trees grow in tropical or subtropical climates; (b) wheat is a crop in most of the world; the flower of (c) the cotton plant produces fibers that are woven into fabric; the potent alkaloids of (d) the beautiful opium poppy have influenced human life ...

This Special Issue is gathering all types of articles (original research papers, reviews, methods papers, opinions, etc.). It focuses on the following topics: 1) plant ecology (e.g., the impacts of humans, climate, plants, animals, topography, and microorganisms on plant diversity); 2) plant evolution (e.g., the impacts of genetic evolution and ...

Biodiversity can provide a series of important ecosystem functions and ecosystem services, which meet the needs of human beings. Plants are the biological group with the highest carbon content on earth, their diversity has attracted increased attention. The interpretation of plant diversity patterns and drivers is crucial for the conservation and utilization of plant resources and is also one ...

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1. Introduction. The conservation of plant diversity has received considerably less attention than the conservation of animals, perhaps because plants lack the popular appeal of many animal groups (Goettsch et al., 2015).As a result, plant conservation is greatly under-resourced in comparison with animal conservation (Havens et al., 2014).Yet plants are much more important to us.

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Past papers Textbooks. Mathematics. ... As an introduction to the diversity of plants, you can do a short walk around your school, aimed at developing a greater awareness of the plants in and around the school, and specifically those that produce seeds and those that do not. Also encourage learners to take note of leaf shape, size, flowers, etc.

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Here is your short essay on Plant Diversity. There are nearly 3, 92,000 species of flowering and non-flowering plants which have been identified. Depicts details on the total number of plant species recorded so far and the number believed to exist on earth. The number of plant species that occur in India is more than 45,000, which represent ...

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Importance of Genetic Diversity in Plant Genetic Resources. Genetic diversity is the genetic base for crop improvement . Diverse PGRs enable plant breeders to develop or improve crop varieties with desirable qualities. ... These techniques also help in the conservation of elite and pathogen-free plants in the short-, medium- and long-term. 5.7. ...

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Essay on Diversity in Plants. Students are often asked to write an essay on Diversity in Plants in their schools and colleges. And if you're also looking for the same, we have c

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Feature Papers in Plant Diversity. Special Issue Editors. Special Issue Information. Published Papers. A special issue of Diversity (ISSN 1424-2818). This special issue belongs to the section "Plant Diversity". Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 36950.

AimThe global patterns of phytophagous eriophyoid mite species diversity have been poorly studied for several decades. In a previous paper, we compiled a dataset covering 97% (4278/4400) of named eriophyoid mite species and 22,973 occurrence sites from 102 countries (Li et al., 2023). Using this dataset, we aimed to predict the global distribution patterns and species diversity of eriophyoid ...

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Genetic Diversity, Conservation, and Utilization of Plant Genetic Resources

Romesh kumar salgotra.

1 School of Biotechnology, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha, Jammu 180009, India

Bhagirath Singh Chauhan

2 Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Gatton, QLD 4343, Australia

Associated Data

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Plant genetic resources (PGRs) are the total hereditary material, which includes all the alleles of various genes, present in a crop species and its wild relatives. They are a major resource that humans depend on to increase farming resilience and profit. Hence, the demand for genetic resources will increase as the world population increases. There is a need to conserve and maintain the genetic diversity of these valuable resources for sustainable food security. Due to environmental changes and genetic erosion, some valuable genetic resources have already become extinct. The landraces, wild relatives, wild species, genetic stock, advanced breeding material, and modern varieties are some of the important plant genetic resources. These diverse resources have contributed to maintaining sustainable biodiversity. New crop varieties with desirable traits have been developed using these resources. Novel genes/alleles linked to the trait of interest are transferred into the commercially cultivated varieties using biotechnological tools. Diversity should be maintained as a genetic resource for the sustainable development of new crop varieties. Additionally, advances in biotechnological tools, such as next-generation sequencing, molecular markers, in vitro culture technology, cryopreservation, and gene banks, help in the precise characterization and conservation of rare and endangered species. Genomic tools help in the identification of quantitative trait loci (QTLs) and novel genes in plants that can be transferred through marker-assisted selection and marker-assisted backcrossing breeding approaches. This article focuses on the recent development in maintaining the diversity of genetic resources, their conservation, and their sustainable utilization to secure global food security.

1. Introduction

Genetic diversity is the amount of genetic variability present among individuals of a variety or a population within a species. It is the product of the recombination of genetic material (DNA) during the inheritance process, mutations, gene flow, and genetic drift [ 1 ], and it results in variations in DNA sequence, epigenetic profiles, protein structure or isoenzymes, physiological properties, and morphological properties. The diversity among plant and animal populations is determined by the hereditary material present in the reproducing members of the population. Genetic diversity is the main driving force for the selection and evolution of populations. Within crop species, the selection of individuals can be natural or artificial, depending upon the variation present [ 2 ]. Genetic diversity can be distilled down to the alleles of a gene present in the population, their effects, and their distribution. Genetic diversity is crucial for a healthy population as it maintains different genes that could lead to resistance to pests, diseases, or other stress conditions. It also enables individuals to adapt to various biotic and abiotic stresses. Under environmental changes, different crop varieties survive due to the presence of genetic variation, which enables the varieties to adapt. However, the varieties with little or no genetic diversity could become susceptible to biotic and abiotic stresses. Genetic diversity helps breeders to maintain the crossbred varieties, which leads to sustaining the desirable traits of the varieties, such as quality characteristics and tolerance to various stresses.

In general, plant genetic resources (PGRs) are the total hereditary material, which includes all the alleles of various genes, present in a crop species, including horticulture and medicinal plants, and their wild relatives. They can also be defined as any type of reproductive or vegetative propagating material of the plant species. PGRs include newly developed varieties, cultivated crop varieties, landraces, modern cultivars, obsolete cultivars, breeding stocks, wild forms, weedy forms, wild species of cultivated crops, and genetic stocks, including current breeders’ lines, elite lines, and mutants. These are the building blocks for the genetic improvement of agricultural and industrial crops [ 3 ]. Most of the agro-industry and agro-processing sectors also rely on PGRs. These are the pillars of crop development programs, and world food security depends upon the extent of genetic diversity present in PGRs [ 4 ]. PGRs are used in crop improvement programs, particularly in the varietal developmental programs. These resources are also used in systematic studies, such as evolutionary biology, cytogenetic, biochemical, physiology, phylogenetic, ecological research, pathology, molecular studies, etc. PGRs encompass all cultivated, wild relatives of cultivated species, traditional cultivars, landraces, and advanced breeding lines of plants [ 5 ]. The demand for these PGRs will increase in the future to feed the ever-increasing global population. Moreover, the precedential increase in the world population has resulted in the over-exploitation of PGRs, which has led to the genetic erosion of important germplasm from habitats. Food security issues are of global significance, and genetic resources are being lost at alarming rates due to anthropogenic effects such as genetic erosion, over-exploitation of PGRd, population growth, and climate change. Moreover, with the development and introduction of high-yielding crop varieties, genetic diversity among plant genotypes is declining [ 6 ]. The situation is further exacerbated by the frequent recurrence of biotic and abiotic stresses, resulting in a huge loss of PGRs. To avoid this catastrophic situation, there is a need to protect these valuable resources from genetic erosion and use them judiciously. To meet the current, as well as future, global challenges, PGRs need to be explored, collected, conserved, and utilized sustainably. Additionally, the survey, exploration, collection, preservation, and sustainable utilization of PGRs in an organized way is the responsibility of all nations. Researchers, policymakers, and planners have already begun to plan for the proper conservation and sustainable utilization of PGRs for the benefit of society [ 7 ].

Maintaining diversity in PGRs is vital for the development and genetic improvement of crop varieties. Presently, the plant species extinction rate is skyrocketing, and life on Earth is facing a sixth mass extinction event caused by climate change and anthropogenic activities, which may lead to ecological collapse [ 8 ]. The Leipzig Declaration [ 9 ] emphasized saving the seed and planting material to avoid genetic vulnerability and shortage of food under adverse conditions. The diverse gene pool of plant species, such as wild species, landraces, breeding stock, etc., could hold the tools for survival and adaptation under adverse climatic conditions [ 10 ]. The conservation and sustainable utilization of these valuable resources is crucial to ensure food security for future generations. Genetic resources should be easily available to plant breeders for the continuous development of new crop varieties. PGRs are an important reservoir of disease- and insect/pest-resistant genes, through which improved and immune crop varieties can be developed. In the present scenario of climate change, PGRs have played a significant role in the development of climate-resilient crop varieties to strengthen food security [ 11 ]. By using PGRs, crop varieties are being developed with better yield and quality traits along with resistance to biotic and abiotic stresses, such as diseases, insect pests, flooding, salinity, and drought. Additionally, developing countries rely on PGRs to create more diverse crops. The need for PGRs has risen continually for developing varieties of different crops such as cereals, pulses, vegetables, fruits, and ornamentals [ 11 ].

Today, the conservation and sustainable use of PGRs is a priority of the global community to solve issues surrounding food security and other problems arising from increased population growth. In the future, these resources will completely vanish if proper and stringent PGR conservation practices and policies are not implemented [ 11 ]. This challenge can be overcome by bringing all stakeholders, including farmers, ethnobotanists, indigenous knowledge-holding people, plant breeders, NGOs, seed banks, and policymakers together to share information, create PGR diversity awareness, develop new technologies, and deploy systematic and scientific conservation. Biotechnological techniques, such as cryopreservation, molecular markers, high-throughput sequencing, and genetic engineering, have improved the conservation of endangered and rare PGRs. Priority should also be given to the exploration of local germplasm and underutilized crop species and the maximum utilization of traditionally local landraces, with the involvement of local people. The Convention on Biological Diversity (CBD) and international undertaking on PGRs [ 12 ] are working in harmony for the conservation and sustainable utilization of PGRs under the umbrella of the Earth Summit of the United Nations Conference on Environment and Development (UNCED). A well-planned strategic and forward-looking vision is required for the conservation and sustainable utilization of these genetic resources.

2. Importance of Genetic Diversity in Plant Genetic Resources

Genetic diversity is the genetic base for crop improvement [ 13 ]. Diverse PGRs enable plant breeders to develop or improve crop varieties with desirable qualities. While developing new cultivars, due consideration must be given to the farmers’ preferences, such as high-yielding varieties, quality, and resistance to diseases and insect pests. In ancient times, humans selected desirable genotypes based on natural genetic variability in the population [ 14 ]. The preference for the development of new crop varieties shifts over a period with environmental changes. Plant breeders develop climate-resilient varieties possessing all the desirable traits, including resistance to various biotic and abiotic stresses. Genetic diversity in the form of mutant lines, wild species, breeding stocks, etc., is used for the improvement and development of modern crop varieties [ 13 ]. For the development of climate-resilient varieties, novel genes tolerant to biotic and abiotic stresses need to be conserved for future use in breeding programs. Additionally, the plant genotypes possessing genes for quality traits and aesthetic properties should be preserved in the available germplasm. Genetic diversity within and between plant species allows plant breeders to select superior genotypes, which can then be used for the development of genetic stock for hybridization programs or the release of a crop variety [ 13 ]. Genetic diversity enables PGRs to adapt to varied climatic conditions [ 14 , 15 ]. Moreover, the negative impact of inbreeding in populations can be reduced by enhancing genetic diversity. Higher levels of genetic diversity in PGRs support resilience to adverse environmental changes, integrity, community structure, and ecosystem functions [ 16 , 17 ]. Additionally, it helps plant breeders to utilize genetically diverse parents in a breeding program to improve the productivity of varieties of agriculture and horticulture crops [ 18 ] ( Figure 1 ).

Different sources of genetic diversity and their potential utilization in the development of new crop varieties.

Genetic diversity in plant species depends on the heritable variation present within and between populations. It occurs due to genetic variation in the nucleotide sequence of DNA, chromosome mutations, and recombination during sexual reproduction [ 19 ]. In the sexual reproduction of plant species, the F 1 and advanced generations are developed by crossing two or more diverse parents. The offspring developed from two genetically diverse parents possess genetic variations because of recombination during meiosis. Hence, genetically dissimilar offspring from parents are produced. However, this is the genetic material of individuals underlying the variability within, as well as between, species [ 20 ]. Generally, genetic diversity can be observed at three levels: diversity between species, diversity between populations within one species, and diversity between individuals within one population. It is genetic variability that provides evolutionary flexibility, resilience, and adaptability in plant species [ 21 ]. Before the identification of diverse parents in plant breeding programs, breeders and biotechnologists used a multitude of techniques for the characterization of the germplasm to know the genetic diversity [ 22 ]. For the characterization of the genetic diversity of PGRs and the identification of superior genotypes, various techniques are used, such as phenotypic or morphological traits, biochemical or allozyme techniques, and molecular techniques.

3. Factors Affecting Genetic Diversity

Genetic diversity changes over time owing to several factors. The main factors responsible for changes in genetic diversity are mutation, selection, genetic drift, and gene flow. Over time, natural and artificial selections play a substantial role in the choosing of superior genotypes, which significantly affects the gene and genotypic frequencies of the population [ 23 ]. As per Charles Darwin’s theory of evolution (1859), the desired genotypes are selected for and passed onto subsequent generations [ 24 , 25 , 26 ]. However, the domestication of desirable genotypes results from the superior genotypes being selected by farmers and breeders and neglects other undesirable genotypes. This leads to a reduction in inferior alleles over generations. During evolution, various morphological, physiological, and biochemical changes take place in plant species and can take different directions under domestication depending on the part of the plant used. Some plant species lose their sexual reproduction during selection for large size of the tuber or root, which is associated with selection for polyploid types, resulting in sterility. Some polyploid plant species, such as allohexaploid wheat and potato, show diploidization behavior during sexual reproduction. Some crops have been turned into annuals from their original form of perennials. In the domestication process, the complete genetic transformation of wild species occurs in the development of modern cultivars through natural and artificial selection [ 23 ]. After some time, some domesticated cultivars become susceptible to diseases and pests, which can be improved by incorporating genes from wild plant relatives [ 27 ]. During the process of domestication, desirable traits have been selected by breeders as per their preferences [ 27 , 28 ]. However, plant breeders prefer to choose crop varieties with a high yield, resistance to biotic and abiotic stresses, wide adaptation, non-shattering nature, large-sized seeds, early maturing, good quality traits, etc. [ 29 , 30 ]. The main factors affecting genetic diversity will be addressed in the following subsections.

3.1. Mutation

Mutations are sudden heritable changes that occur due to aberrations in the nucleotide sequence of DNA. A mutation is the source of genetic variation impacting the phenotype in crop species. Genetic diversity caused by mutations can have neutral, positive, and negative impacts on various characteristics of a plant species. Genetic variations caused by mutations in DNA are the principal cause of changes in the allele frequencies in a population besides selection and genetic drift. From the beginning, natural or spontaneous mutations have played a significant role in creating the genetic variation that has led to food security [ 31 ]. Mutations are the ultimate source of plant evolution when they frequently encounter environmental changes. Mutation rates proceed rapidly in response to environmental changes or even changes in the demographical locations related to the socio-economic conditions of the human population in a geographical area. Stress-inducible mutagenesis has been observed because of the use of different external inputs which accelerate adaptive evolution in plants. During mutagenesis, many kinds of genetic changes have been observed such as insertions, deletions, copy number variations, gross chromosomal rearrangements, and the movement of mobile elements. Earlier plant breeders utilized natural mutations as the main source of genetic variation for improving and developing crop varieties. However, modern technologies have accelerated the process by inducing mutation through mutagenesis The concept of mutation breeding was introduced to create more genetic diversity among crop species to improve traits such as disease and insect pest resistance, tolerance to abiotic stresses, and nutritional enhancement in crop varieties [ 32 ].

3.2. Selection

Natural and artificial selections act on the phenotypic characteristics of the plant species. The phenotypic expression of the plant species depends upon the heritable and non-heritable components in which the genotype–environment interaction also plays a significant role. The selection of superior genotypes depends on the availability of genetic variation present in the plant species. Artificial selection is effective only when sufficient genetic variation is present in the population. The genetic improvement of a genotype depends on the magnitude of genetic variability present in the population, as well as the nature of the association between different components. For example, the level of association of yield traits with other characteristics of the plant species enables the selection of various traits at a time [ 33 ]. Plant breeders make effective selection depending on the presence of substantial genetic variation in the population to enhance the maximum genetic yield potential of crop varieties [ 34 ]. It also helps in selecting better parents to be used in hybridization programs. Hence, the effective selection of genotypes in a population also depends on the degree of genetic variation in the population.

3.3. Migration

Migration is the movement of alleles from one species to another or from one population to another. It occurs through the movement of pollen and seed dispersal and planting material such as rhizomes, suckers, and other vegetative propagating materials. The rate of migration is affected by reproduction cycles and the dispersion of seeds and pollens. Migration can also occur through the moving or shifting of the germplasm from one area to another, which results in the mixing of two or more alleles through pollen and seeds [ 35 ].

3.4. Genetic Drift

Genetic drift is a mechanism in which the gene and allele frequencies of a population change due to sampling errors over generations. The sampling error changes the allele frequencies by chance, which ultimately changes the genetic diversity over generations. Every pollen grain has a different combination of alleles and can be carried by insects, wind, humans, or other means for hybridization with compatible flowers, largely determined by chance. Thus, in every reproduction cycle, the genetic diversity in crop species is lost at every generation through these chance events [ 36 ].

4. Factors That Cause Genetic Vulnerability

Over the past century, it has been observed that the genetic diversity in wild populations is declining globally [ 16 , 37 ]. Genetically distinct populations for most species are also declining due to the shrinkage of geographic ranges and lack of proper management and conservation practices [ 38 , 39 , 40 ]. Most genetic diversity is lost due to infrastructure development, climate change, habitat fragmentation, population reduction, overgrazing, and overharvesting [ 41 ]. Besides this, the following subsections describe the major components responsible for the genetic vulnerability of genetic resources.

4.1. Narrow Genetic Base of Crop Varieties

The main reason for genetic erosion and vulnerability is the cultivation of genetically uniform cultivars with a narrow genetic base. Indigenous or traditional crop varieties have a broad genetic base, and these cultivars can tolerate various biotic and abiotic stresses [ 42 ]. Traditional crop varieties have a low genotype–environment interaction, enabling the genotypes to withstand an epidemic of disease, insect pest incidence, and other adverse environmental conditions [ 43 ]. Moreover, pathogen races are less prone to infesting traditional varieties because of the broad genetic base of these varieties compared to the modern released varieties that have common parents. Hybrids have been developed by crossing different genetically uniform inbred lines, which significantly decreased genetic diversity. Additionally, most high-yielding crop varieties have been developed by crossing common parents possessing similar genetic backgrounds, which can significantly reduce the genetic bases of the varieties [ 22 , 44 ].

4.2. Wide Spread of Dominant Varieties

The widespread cultivation of a single crop variety over a large area causes genetic vulnerability. These varieties may perform well for a short period but may become susceptible to several diseases and pests. Vertical resistance occurs due to the presence of oligogenic or monogenic resistance, and horizontal resistance occurs due to the presence of polygenes. Sometimes the vertical resistance present in the modern cultivar may show resistance against a disease, but will become susceptible if the pathogen evolves. In vertical resistance, the race of the pathogen or the insect pest biotype interacts with the host and overcomes the monogenic resistance present in the modern cultivar, and the variety becomes susceptible to a particular pathogen or biotype.

4.3. Unplanned Introduction of New Plant Species

Sometimes, new high-yielding plant species are introduced and used in a breeding program without proper screening for disease and insect pest resistance, which may result in an unpredicted epidemic of diseases. An example of this is the unplanned introduction of the Texas male sterile (TMS) genotype of maize for the development of hybrid maize genotypes in the USA in 1970. Newly developed maize hybrids had all the desirable characteristics and resistance to most of the common maize diseases. The TMS hybrids were widely cultivated in the USA, covering more than 90% of the maize area. However, these hybrids were susceptible to fungal strains and southern corn leaf blight ( Helminthosporium maydis ). The southern corn leaf blight disease colonized and spread widely, and the whole maize crop was wiped out. If the TMS, a source of male sterility, had been tested and screened properly before use in hybrid breeding programs, or if the monoculture of TMS hybrids had been avoided, the spread of this epidemic could have been countered [ 45 ].

5. Conservation of Plant Genetic Resources

Since the beginning of agriculture, for a time, the selection, cultivation, and conservation of seeds of locally acclimated plants, also known as called “landraces”, were practiced [ 46 ]. This process continued until the rediscovery of Gregor Mendel’s work in the 20th century. This work led to the introduction of breeding programs for the development of high-yielding and stress (biotic and abiotic)-tolerant crop varieties. In the middle of the last century, it laid the foundation for the “Green Revolution” and brought about an exponential increase in agricultural production. However, this led to the replacement of landraces and the expansion of the monoculture cropping system. Over 75% of the genetic diversity in PGRs and 90% of the crop varieties were lost and disappeared from farmers’ fields [ 47 ]. Now, it is of paramount importance that the remaining PGRs be conserved to sustain the agricultural production system in this era of climate change, global environmental problems, and booming population growth [ 48 ].

Since the 16th century, more than 80,000 plant species have been collected and preserved in about 3400 gardens across the world [ 49 ]. The main objective of this effort is to conserve the PGR diversity and wild species of crop plants to be used in breeding programs. In the mid-20th century, PGRs for food and agriculture (PGRFA) were preserved ex situ in specialized repositories, often termed gene banks. These gene banks are focused on inter-and intra-specific crop diversity. Presently, more than 17,000 regional, national, and international institutions are dealing with the conservation and sustainable use of PGRFA [ 49 ]. Additionally, 711 gene banks and 16 regional/international institutions/centers are spread over 90 countries, conserving more than 5.4 million accessions from over 7051 genera. The focus is to conserve the crop species, including crops’ wild relatives, landraces, modern cultivars, genetic stock, and breeding materials [ 50 ]. However, various international treaties have been implemented in harmony with the CBD for conservation, sustainable utilization, equity in benefit-sharing, and the safe handling of genetic resources.

5.1. International Treaty on Plant Genetic Resources for Food and Agriculture

The International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA) came into force in 2004. ITPGRFA works in harmony with the CBD for sustainable agriculture and food security. The objective of the treaty is the conservation and sustainable use of plant genetic resources for food and agriculture and the fair and equitable sharing of the benefits arising from their use. The conservation and sustainable use of PGRFA are essential to achieving sustainable agriculture and food security, for present and future generations, and are indispensable for crop genetic improvement in adapting to unpredictable environmental changes and human needs.

5.2. Nagoya Protocol

The Nagoya Protocol, which came into force in 2014, aims to access genetic resources and encourage the fair and equitable sharing of benefits arising from their utilization. The Nagoya Protocol helps in ensuring benefit-sharing, creates incentives to conserve and sustainably use genetic resources, and therefore, enhances the contribution of biodiversity to development and human well-being.

5.3. Svalbard Global Seed Vault

The Svalbard Global Seed Vault situated in Norway safeguards duplicate seed varieties from almost every country in the world. The Seed Vault is owned and run by the Ministry of Agriculture and Food on behalf of the Kingdom of Norway and is established as a service to the world community. The Global Crop Diversity Trust provides support for the ongoing operations of the Seed Vault, as well as funding for the preparation and shipment of seeds from developing countries to the facility. The Nordic Genetic Resource Center (NordGen) operates the facility and maintains a public online database of samples stored in the seed vault. It provides insurance against both incremental and catastrophic loss of crop diversity held in traditional genebanks around the world. The Seed Vault offers long-term protection for one of the most important natural resources on Earth. The main purpose is to backup genebank collections to secure the foundation of our future food supply.

5.4. The Cartagena Protocol on Biosafety

The Cartagena Protocol on Biosafety’s goal is to provide safety in the handling of genetic resources, particularly genetically modified organisms. It is an international agreement that aims to ensure the safe handling, transport, and use of living-modified organisms (LMOs) resulting from modern biotechnology that may have adverse effects on biological diversity, while also taking into account risks to human health.

The ever-increasing demand resulting from the explosive growth rate of the human population worldwide, and global warming, have forced world communities to think about the sustainable use of PGRs. The conservation of PGRs, including landraces, obsolete varieties, breeding material, wild species, and their wild relatives, is of utmost importance to secure future food security [ 44 ]. The vanishing of valuable genetic resources invoked the world’s communities to explore, collect, and preserve PGRs and maintain genetic diversity, as well as sign the CBD event in Rio de Janeiro in 1992. The importance of PGRs and biodiversity conservation was the main international issue discussed at the convention [ 44 ]. The CBD was organized with three main objectives: (i) the conservation of biodiversity, (ii) the sustainable use of its components, and (iii) the equitable sharing of benefits arising from the use of genetic resources. There is an urgent need to conserve genetic resources for the welfare of human beings and future food security, and to avoid the loss of valuable novel genes. Effective policies should be implemented to evade the extinction of valuable PGRs. There are various methods to conserve biodiversity, such as (i) in situ conservation, (ii) ex situ conservation, and (iii) biotechnological strategies/approaches ( Figure 2 ). The genetic diversity in PGRs, in situ or on farms/fields, is creating awareness in society at large about the importance of agrobiodiversity. In situ and ex situ conservation are complementary strategies to prevent the mass erosion of genetic resources. The utilization of crop genetic diversity is necessary for the development and release of new, well-adapted, and improved varieties for global food security.

Different strategies used for in situ and ex situ conservation of plant genetic resources.

5.5. In-Situ Conservation

In in situ conservation, genetic resources are conserved in their natural habitat, and the species are maintained in their original place. The plant species are conserved where they are found and are maintained in their original location [ 51 ]. In in situ conservation, the process of evolution is allowed to occur naturally with minimum interventions from humans. In this system, many wild plant species are conserved, especially forest and wild fruit crops. In situ conservation permits the plant species to evolve so that genetic diversity can be fostered. This process works via two methods: (i) farm/field conservation and (ii) genetic reserve conservation. Though both are concerned with the conservation and maintenance of diversity of genetic resources, on-farm conservation concerns traditional crop varieties or farming systems, while the latter deals with wild species in natural habitats [ 4 , 11 ]. In genetic reserve conservation, the area is defined by a location where genetic diversity has to be maintained through active and long-term conservation, such as a forest reserve area. In on-farm conservation, locally developed landraces are sustainably managed. Additionally, farmers conserve wild relatives and weedy forms within the existing farming system. Farmers select desirable plants for further cultivation; hence, a continuous process of evolution takes place. The in situ method of conservation allows the open pollination of different genotypes, and the resultant population of different genotypes possesses several alleles. However, to avoid natural calamities and the adverse effects of climate change, both in situ and ex situ conservation should be adopted complementarily [ 4 , 11 ].

5.6. Ex-Situ Conservation

Ex situ conservation is the conservation of different genetic resources outside their natural habitat. It involves the conservation of seed gene banks, plant tissue culture, cryopreservation, greenhouses, etc. It is the process of conserving endangered and overexploited genetic resources outside their natural habitat, which otherwise may experience habitat destruction and degradation, and every PGR may go extinct. Therefore, ex situ conservation is an alternate method of conserving valuable genetic resources [ 52 ]. In this method, PGRs are saved from extinction that would result from natural calamities, human interference, climate change, over-exploitation, and overutilization. The collected genetic resources should be well evaluated and characterized to avoid duplication, documented, and conserved under artificial conditions to be safe from external threats [ 4 ]. Among the various techniques of ex situ conservation, the seed storage technique is the most convenient and easiest for the long-term storage of seeds [ 4 , 11 ]. Orthodox seeds of food crops are used for storage as they can tolerate low temperatures and intense dehydration. In ex situ conservation, about 45% of the stored accessions are seed materials of cereal crops such as rice, wheat, maize, oat, triticale, rye, sorghum, and barley, followed by food legumes (15%), forages (9%), and vegetables (7%) [ 46 , 49 ].

Generally, the conservation of collected seeds is carried out in two ways: base collection and active collection. Base collection is the collection and maintenance of seed samples for long-term conservation. In this case, the seed samples are stored for the maximum time of seed viability at −18 to −20 °C [ 53 ]. In the base collection method, the moisture content of the seed to be stored should be between 3% and 7%, depending on the species. In the active collection method, the seed samples are stored for immediate use. Seed samples are stored for 10–20 years and should have at least 65% viability. In the active collection method, the moisture content varies from species to species, i.e., between 7% and 11% for seeds with good storability and between 3% and 8% for seeds with poor storability. It also depends on the temperature under which the seed samples are stored [ 54 ]. However, depending on the storage duration, these are categorized into three basic types: (i) long-term storage: when the seed samples are stored in facilities of base collection and are maintained at −18 to −20 °C; (ii) medium-term storage: when the period of storage is not more than 5 years, and seed samples are stored at a temperature between 0 °C and 10 °C with a relative humidity of 20–30%; and (iii) short-term storage: where the seed samples are stored for between 1 year and 18 months. For the latter, the temperature ranges between 20 °C and 22 °C, and the relative humidity should be 45–50%, where the seed can be stored for up to two years without losing its viability [ 54 ]. For long-term ex situ conservation, seed storage is the most low-cost and widely adopted storage method. It involves the desiccation of seeds and even storage in low-temperature conditions. However, the recalcitrant seeds and vegetatively propagated plant species do not survive under low temperatures like orthodox seeds. This method is significant for the conservation of forest and tree species. Even novel PGRs can be conserved in the home garden for future use in breeding programs. The ex situ conservation method enables the conservation of novel genes/alleles and ensures their sustainable use in crop improvement programs. The ex situ conservation of PGRs was started in the mid-20th century to slow the rapid loss of biodiversity with modern high-yielding crop varieties. The farmers replaced their traditional cultivars with improved ones [ 53 ]. This method is also helpful in the protection and conservation of wild relatives [ 55 , 56 ]. Ex situ conservation methods have been used for conserving important PGRs in several institutes [ 3 , 53 ] ( Table 1 ).

Important research institutes conserving and maintaining PGRs.

5.7. Biotechnological Approaches

Plant biotechnology tools provide new opportunities for the conservation of genetic resources using various in vitro culture techniques. Various biotechnological tools, such as cell and tissue culture and other micropropagation techniques, have greatly contributed to the storage and transportation of PGRs [ 57 ]. Cell and tissue culture techniques are in use for the mass multiplication and production of PGRs in a short time for further conservation and transportation under aseptic conditions. Apart from this, next-generation sequencing (NGS), cell fusion techniques, recombinant technologies, proteomic structural biology, protein engineering, and genome editing techniques have opened new avenues and options for conserving genetic resources with increased precision. These technologies help in the conservation of rare and endangered species, ornamental species, forest species, medicinal species, and other vegetatively propagating plant materials [ 51 ]. When the biological material of PGRs (such as seeds or organs) cannot be propagated and stored using traditional methods, biotechnological tools, such as in vitro culture, cryopreservation, and molecular biology, can be used. Sometimes, reproductive barrier problems existing in some endangered and rare plant species can be solved via biotechnological interventions [ 58 ]. The following subsections highlight the main biotechnological techniques used for PGR conservation, which are not possible under normal storage systems. These techniques also help in the conservation of elite and pathogen-free plants in the short-, medium- and long-term.

5.7.1. In Vitro Propagation

In vitro gene banks are where PGRs are stored in an artificial nutrient medium. This is an alternative method to conserving the vegetative propagated plant genetic material [ 59 , 60 ]. The in vitro conservation method is well recognized by global agencies such as the International Board for Plant Genetic Resources (IBPGR) for safe transportation under regulated phytosanitary control. The main advantages of this technique are insect- and disease-free material, mass multiplication, no genetic erosion, reduced space and labor requirements, and less time taken to obtain a new plant. This technique helps to scale up the production of quality planting material throughout the year. In in vitro methods, the callus is produced from explants such as seeds, leaves, tubers, shoots, and nodes, from which a whole plant is regenerated. In in vitro techniques, an effective conservation method is required once cultures are established and the plant genetic material is multiplied sufficiently. This can be achieved by regularly subculturing the plants onto fresh media. However, there is a risk that subculturing may lead to microbial contamination and chances of somaclonal variations.

The successful production and propagation of genetically stable plants from cultures are prerequisites for in vitro conservation. Shoots are used for slow-growth storage to avoid somaclonal variations. This slow-growth storage is optimal for the medium-term conservation of PGRs [ 61 , 62 , 63 ]. In this method, the targeted germplasm is stored under plant tissue culture conditions and maintained on nutrient gels for 1 to 15 years with intermittent subculturing. Several techniques are optimized to slow the rate of growth, such as low-intensity light with lower temperatures or a reduced photoperiod. Sometimes, the slow growth of cold-tolerant plant species is maintained by employing a temperature range of 0–5 °C, and for tropical plant species, a temperature range of 15–20 °C. The use of growth retardants in culture media and cutting the supply of oxygen is carried out at different levels to slow down the growth of plantlets [ 64 ].

5.7.2. Cryopreservation

The cryopreservation technique involves the storage of biological plant tissue for conservation at ultra-low temperatures (−196 °C), mostly using liquid nitrogen. In cryopreservation, the plant species can be stored for a long period as all the activities, such as cellular metabolism and cell division in recalcitrant seeds and vegetatively propagated plant material, stop. In this approach, no sub-culturing is required, and the chances of somaclonal variations are also reduced [ 65 , 66 ]. The cryopreservation technique ensures cost-effective and safe long-term conservation of plant species; a wide range of plant species can be stored using this technique. In cryopreservation, a cryotherapy technique is also applied to eradicate systemic plant pathogens. In this technique, only meristem cultures or shoot apices are recommended because of their high rate of viability following an extended storage time and because they are virus-free plant materials [ 67 ]. In the cryopreservation technique, the first step is to remove all freezable water content from tissues using osmotic dehydration or a physical approach, followed by ultra-rapid freezing [ 68 ]. The freezable water content can be removed using freeze-induced dehydration and vitrification methods. In vitrification, crystalized ice formation is avoided, and the liquid phase is directly converted into an amorphous phase [ 69 ].

5.7.3. DNA Banks

Advances in molecular biology have made the conservation of endangered and rare species complementary. Genetic resource conservation through DNA is a cost-effective form of conserving PGRs. In biodiversity, many species are difficult to conserve and are at the stage of extinction. DNA storage may be one of the best alternatives to conserve the genetic diversity of these resources, which could possess novel genes/alleles that could aid in future food security. In a gene bank, genomic fragments consisting of individual genes or entire genotypes are conserved in a gene library or a library of DNA samples. Genetic information can be stored in the form of DNA, RNA, and cDNA. These libraries are the primary source of important germplasm for future scientific research worldwide. DNA conservation is an alternative method of conserving PGRs, where the genetic materials are difficult to conserve or threatened because of wild populations or climate change [ 70 ]. The genetic material, in the form of DNA, can be stored at −20 °C for up to 2 years for short- and mid-durations. However, for long-term storage, the genetic material can be stored at −70 °C with the help of liquid nitrogen. For the preservation of DNA, there are some DNA banks, such as the Australian Plant DNA Bank of Southern Cross University, the Royal Botanic Garden (UK), the Leslie Hill Molecular Systematics Laboratory, and the US Missouri Botanical Garden. Among these, The Royal Botanic Garden (UK) is the oldest and the most comprehensive DNA bank, encompassing more than 20,000 DNA samples of all plant families. Like other techniques of PGR conservation, DNA conservation can neither constitute the whole plant from conserved DNA nor recover the original genotypes. In these techniques, conserved DNA in the bank is first artificially introduced into the somatic cells, and then, the whole plant is regenerated using in vitro tissue culture techniques [ 51 ].

5.7.4. Digital Sequence Information

Digitized molecular data are vital to numerous aspects of scientific research and genetic resource use. Substantial advances in DNA sequencing over the last decades hold great potential to enhance food security and the sustainable use of global biodiversity, benefiting the world’s poorest people. Digital Sequence Information (DSI) plays a crucial role in catalyzing research applications that can contribute to international societal and biodiversity conservation targets. There are concerns over access to genetic resources and the absence of benefit sharing by provider countries. Open access to DSI might exacerbate this, which is leading to increasing policy interventions and restricted access to genetic resources and DSI. However, benefit sharing related to DSI is difficult to identify and hindered by the lack of clear international governance and legislation, which, in turn, has led to a reluctance to make DSI publicly and freely available.

6. Utilization of Plant Genetic Resources in Crop Improvement

Before modern cultivated crop varieties, landraces had more genetic diversity. Modern varieties are developed for specific traits, such as high yield, disease resistance, insect pest resistance, stress tolerance, and the improvement of nutritional characteristics. The plant breeders select diverse parents from PGRs in crossing programs to develop new crop varieties [ 71 ]. New crop varieties take at least 8–11 years to develop and may last for 5–6 years under cultivation. However, these varieties can be improved further by incorporating novel genes/alleles from wild relatives or wild species. The wild relatives and landraces are rich sources of novel genes resistant to biotic and abiotic stresses, and these are easily crossable with the cultivated crop varieties [ 72 ]. PGRs can be used in breeding programs in four ways: (i) the development of pre-breeding materials to be used in traditional breeding methods, (ii) the development of genetic stock as a source of resistance to various biotic and abiotic stresses and quality traits, (iii) the characterization and identification of PGRs for male sterility for the development of hybrids [ 73 ], and (iv) the development of modern cultivars by transferring the gene of interest from different genetic resources to popular crop varieties. PGRs are also used to increase genetic variation in the breeding population, incorporate genes to reduce the bottlenecks of the varieties, and develop hybrids, i.e., composites or synthetics.

Genomic Tools for Efficient Use of Plant Genetic Resources

With the advent of modern biotechnological techniques, the efficiency of plant breeders has significantly increased in the development and improvement of crop varieties. Next-generation sequencing (NGS), high-throughput sequencing (HTS), and high-throughput phenotypic (HTP) techniques enable more efficient use of PGRs. Among the various available techniques, DNA-based techniques are more reliable and widely used in crop improvement programs. Unlike other markers, molecular markers are not influenced by the environmental changes and developmental stages of plants [ 74 ]. Molecular markers—such as restriction fragment length polymorphisms (RFLPs), random amplified polymorphic DNA (RAPD), amplified fragment length polymorphisms (AFLPs), inter-simple sequence repeats (ISSRs), diversity array technology (DArT), simple sequence repeats (SSRs), single nucleotide polymorphisms (SNPs), etc.—are widely used in the molecular characterization of genetic diversity present within and between plant populations. Among the various molecular markers, SSR markers are widely used to characterize genotypes [ 22 , 75 ]. DNA-based markers are more efficient in the evaluation of the genetic diversity of endangered and rare species. The main advantages of molecular markers are that any small sample of plant material can be used for genetic diversity analysis. Molecular markers have been widely used to study genetic diversity, and different core collections of PGR accessions have been developed in crops such as rice [ 66 , 76 , 77 ], wheat [ 78 ], mungbean [ 79 ], soybean [ 80 ], common bean [ 81 , 82 ], pigeon pea [ 83 ], chilli [ 84 ], potato [ 85 ], carrot [ 86 ], tomato [ 87 ], oil palm [ 88 ], cotton [ 89 ], mulberry [ 90 ], barnyard [ 91 ], legume crops [ 92 ], and other vegetable and horticulture crops [ 93 ].

With the advances in high-throughput sequencing techniques, SNP markers are preferred for use in crop improvement programs. Various QTLs have been identified by developing a biparental population using PGR populations [ 94 , 95 , 96 ]. Besides the molecular characterization of the germplasm of PGRs for genetic diversity studies, molecular markers are widely used in plant breeding approaches, such as (i) the molecular marker-assisted testing of breeding materials for parental selection, assessing the level of genetic diversity, studying heterosis, the identification of genomic regions under selection, and the assessment of cultivar purity and cultivar identity [ 35 , 97 , 98 , 99 , 100 , 101 , 102 ]; (ii) marker-assisted recurrent selection (MARS) [ 103 ]; (iii) marker-assisted backcross breeding (MABB) [ 104 ]; and (iv) marker-assisted gene pyramiding [ 105 ] and genomic selection for complex traits [ 106 ]. Important crops have had biotic and abiotic resistance and quality traits introgressed through MAS and MABC/MABB approaches [ 66 , 75 , 92 ] ( Table 2 ).

Improvement of various crops using biotechnological tools.

MAS—marker-assisted selection; MABB—marker-assisted backcross breeding; MABC—marker-assisted backcross.

Biotechnological tools have been efficiently used for the improvement of susceptible crop varieties. However, for the sustainable utilization of genetic resources, advanced techniques, such as NGS, HPG, and HTP, should be used to develop new crop varieties to ensure food security in the near future.

7. Conclusions

To meet the ever-increasing demand for food production, crop diversification, climate-resilient farming, etc., PGRs should be used for sustainability for future food security. However, the efficient use of PGRs can help to meet these needs, and one of the major challenges in the PGR community is to improve access to PGR collections by increasing the amount of information available about collections, through conservation, by participating in pre-breeding activities, etc. A great challenge in the PGR community is the increased demand for PGRs in the wider farming and breeding community. Maintaining genetic diversity, the conservation of PGRs, and sustainable utilization should be the priority of national and international communities. The proper monitoring of genetic erosion and genetic diversity vulnerability is crucial to protecting rare and endangered plant species. As no single technique of conservation is perfect, there is a need to practice in situ and ex situ conservation complementarily. Technical as well as financial support should be provided to farmers and local people for the proper conservation of plant genetic resources. For the management and sustainable use of PGRs, the capacities of local communities, indigenous people, farmers, breeders, extension workers, and other stakeholders, including entrepreneurs and small-scale enterprises, should be strengthened. The proper evaluation, characterization, and documentation of endemic plant species and their exact habitats should be prioritized. More frameworks and policies should be implemented for the sustainable conservation of landraces and their wild relatives. Biotechnological tools should be used for the characterization of plant genetic resources, conservation, and their utilization in breeding programs. Allele/gene mining for important traits in wild species and wild relatives of crops should be given more importance. The effective utilization of plant genetic resources would contribute to solving constraints that limit crop productivity. High-throughput genotypic and phenotypic techniques should be used for the sustainable utilization of genetic resources for future food security.

Funding Statement

This research received no external funding.

Author Contributions

Conceptualization, R.K.S.; Writing—Original Draft Preparation, R.K.S.; Writing—Review and Editing, B.S.C.; Supervision R.K.S.; Funding Acquisition, B.S.C. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Data availability statement, conflicts of interest.

The authors declare no conflict of interest.

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Here is your short essay on Plant Diversity

There are nearly 3, 92,000 species of flowering and non-flowering plants which have been identified.

Depicts details on the total number of plant species recorded so far and the number believed to exist on earth. The number of plant species that occur in India is more than 45,000, which represent nearly 12 percent of recorded flora of the world.

The huge number of plant species inhabiting the earth show great diversity with respect to their habit, habitat, structure, function and life-span.

They range in size from microscopic bacteria, some of which are some thousandth of cm in diameter, to giant Sequoias which grow to more than loom, in height and may weigh more than 1000 tons. A giant Californian Sequoia may probably be more than 3500 years old. There are certain coniferous plants which are more than several hundred years old.

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Plant form varies with varying environmental conditions. Plants that grow in dry areas and swampy areas vary distinctly. The same comparison can be made between plants found in tropical and polar climates.

The soil factors, wind conditions and the duration of sunlight also determine the forms of vegetation. For example, the sandy soil of coastal plains does not hold water very well. Thus, it can support plants whose leaves are much reduced or modified. But the broad-leaved trees grow better in the soil with more humus.

The origin of plants continues to be a debatable question. Fossil data indicate that the plants have originated nearly 2 billion years back.

In this long span of time, many plants have originated, many more evolved into complex, better adapted ones and still many unknown number who failed to evolve with time have become extinct. At present the large numbers of plants that surround us are the products of this evolutionary process.

The most primitive and the smallest plants in terms of their structural simplicity are the bacteria and algae. Bacteria are mainly known for the diseases they cause to humans and role played in decay and decomposition of organic materials.

The algae, on the other hand, are the simplest photosynthetic plants. However, the term algae do not refer to a single group of plants but to a multitude of its representatives who vary primarily on the basis of pigmentation, complexity of form and elaboration of process of reproduction.

Fungi like the algae are primitive on the scale of plant evolution. These are however, non chlorophylls plants and live as parasites or saprophytic ally on dead, decaying organic debris.

They seem to have an evolutionary development parallel with algae. Lichen is a dual organism, where an association is formed between algae and fungi. Some fungi are synonymous with plant diseases yet others are important in baking industry, alcohol production and in manufacture of antibiotics.

The plants discussed so far, are really numerous and diverse. But the common man is not familiar with these small inconspicuous diverse worlds of plants. To him the term plants refer to some familiar, green leafy land habiting organisms. However, land plants evolved considerably later in comparison to aquatic algae.

During this transition from water to land, it appears that evolution has occurred in two distinct lines. One of these was appearance of conducting or vascular tissues. These plants reached great degree of diversity in form and function. In second line, no specialized vascular or supporting tissues developed and these plants gave rise to no other new forms. Modern descendants of the latter are liverworts, hornworts and mosses. These are collectively called as bryophytes.

These are most primitive of green land plants, predominantly amphibious in habit. Individually, the bryophytes are small inconspicuous and often seen growing in clusters. The vascular plants which represent another line of evolution from the primitive aquatic plants are more than 400 million year old. Club mosses, horsetails, ferns form the conspicuous representative of this type of organisms.

In course of time, a few vascular plants started to produce seeds. Among the earliest seed plants are the pines, cycads, fir trees etc. collectively called gymnosperms? Following these, a special type of flowering plants made its appearance.

These are closed seeded; they are now the dominating forms of plant life. They are not only the highest forms of plant life, but the most diversified and widespread, as well.

A brief survey of plant kingdom shows that some plants may lack roots, stems and leaves, others are non green, some do no, contain the supporting and conducting system Some do not form seeds, other have naked seeds and some plants have flowers, from winch.

Seeds with integument, called fruits develop. Again, the world of plants shows a great diversity in their life cycle pattern. The simplest and earliest forms have haploid plant bodies called thalli, i.e. the gametophyte or haploid or n phase is quite evident in the life cycle. However, saprophyte or diploid or 2n phase is only restricted to zygote or the fusion products of sexual reproductive unit.

These diploid or saprophytic or zygotic phase is very Short lived and never becomes a free living plant at maturity. It undergoes meiosis or reduction division to produce the haploid, free living and independent phase.

When the life cycle pattern of bryophytes are considered, one will find that the plant body is more complex foliose and haploid. However, bryophytes along with saprophytic generation are never an independent, free living plant at maturity. In contrast, the pteridophytes are diploid or saprophytic generation is more prominent and independent.

In the flowering plants like gymnosperms and angiosperms, the saprophytic or diploid (2n) generation reached its zenith of elaboration and gametophytic or haploid (n) generation is parasitic upon it.

They are in the form of gametes. The condition is just the reverse of the pattern of life cycle seen among the thallophytic like algae of fungi. Among the individual divisions of plants like algae or fungi, bryophytes, pteridophytes etc. great degree of diversity in life cycle pattern is also observed.

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Essay On Plants – 10 Lines, Short And Long Essay For Kids

Key Points To Remember When Writing An Essay On Plants For Lower Primary Classes

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Humans have depended on plants for generations for food and medicine. Plants go through photosynthesis and can pull nutrients from the soil and return them to the earth. They also provide clean air to breathe and scrub the atmosphere off pollutants. Many animals depend on plants for survival and live in environments surrounded by them, as they serve as natural habitats. If you are trying to write about plants in English and educate your kids, there are a lot of things you need to know to get started. Read on below to learn how to write an essay on plants for classes 1, 2, and 3.

Plants are valued not just for their beauty but for our well-being. Below are key points to remember on the importance of plants and how to write an essay on the same.

• Start with an introductory paragraph. Write a few simple sentences on how they influence our daily lives.
• Talk about the different types and uses of plants.
• You can also cover plants’ health benefits and briefly add how they improve emotional and mental well-being.
• Conclude with how to pick the best plants for your home, where to start, and why you love plants.

You can write a few lines on plants, but it’s crucial to understand their natural design and processes. We cannot enjoy the quality of life we live and breathe if it weren’t for plants. Here are 5 lines on plants for children:

• Plants do a lot for our environment, and their role is often underestimated.
• Plants in oceans maintain balance in the ecosystem and are essential for the survival of various aquatic species.
• Most plants absorb harmful outdoor gasses and purify the air.
• Plants absorb carbon dioxide and produce oxygen to sustain life on earth.
• The roots of plants bind them to the soil, and photosynthesis is a process that occurs through plants’ leaves.

The countless benefits of plants cannot be denied since plants have existed for thousands of years. You can mention this in your essay for classes 1 and 2. Here are 10 sentences on plants for children:

• Plants purify the air we breathe and help to maintain balance in an ecosystem.
• They reduce the harmful effects of UV rays coming from the sun and cool down the air.
• Plants are crucial to our survival as humans since they produce oxygen which is key to life.
• Transpiration is a process through which plants move water from the soil to the atmosphere.
• Plants give us different resources such as food, gum, herbal medicine, etc.
• Dried hay and straw are plants that are used to feed animals like cows, horses, and sheep.
• Plants make their own food. This process of making food is known as photosynthesis.
• The study of plants is known as Botany.
• Green algae are called primitive plants because they live in water.
• Liverworts are plants that thrive in damp and tiny conditions, often known for lacking vascular tissue.

Plants are always around us; we see them in houses and parks. Writing a short paragraph on plants will enhance kids’ knowledge of the subject.

A plant comprises more than 95% water; every tree we find around us was once a plant many years ago. It’s no surprise that they provide sustenance to living beings; without plants, it would be impossible to have a life on earth. There are three main types of plants – conifers, ferns, and flowering plants. Flowering plants are described as those species that grow leaves such as roses, tulips, dandelions, sunflowers, etc. Conifers are evergreens that grow tall and sometimes have needles instead of leaves. Ferns are non-flowering plants that don’t have leaves or flowers. Blue-green algae originated 3 billion years ago and were known to be the first plants on this earth.

Plants are found in all shapes and sizes and are known to improve our lives. Here’s a short essay for classes 1, 2, and 3 on plants:

Trees are the most significant plants, and they are full of leaves during the summers. Plants are the beauty of the earth. As humans, we depend on plants for food and various other things like gum, rubber, and paper for our consumption. Through photosynthesis, plants can make their own food. Plants cannot run away from animals to protect themselves but have specific safety mechanisms. Sharp spines and allergic reactions triggered by leaves are common ways to defend against prey in nature. Plants provide various benefits for people. They can purify the air and help keep us healthy. Some plants can even provide medicine or food when needed. Plants provide a variety of vegetables, fruits, oxygen, and other things and assist in controlling carbon dioxide in the atmosphere. Botany is the study of plants and their species and features. Plants are important because they provide habitats for animals and aquatic species and make other valuable things like rubber, resin, vegetable oils, and natural dyes. Fossil fuels like coal and petroleum are also by-products of plants used in automobiles.

Photosynthesis occurs during the day, and plants require sunlight, oxygen, and nutrients from the soil to survive and thrive. Unlike humans, plants are anabolic and catabolic by nature. Below is a long essay for class 3 kids on plants:

Plants are necessary for humans to survive and thrive. Chlorophyll in plant leaves absorbs light from the sun and carbon dioxide from the atmosphere, releasing oxygen into the environment.

During respiration, oxygen gets utilised, and CO2 is given out. If the number of plants in our environment decrease, it can pose significant health hazards since there will be no control over air pollution. Plants provide animals with food and edible parts such as fruits and nuts. The roots of many plants are ground into fine powders and store medicinal value, and many plants, such as the aloe vera and neem plant, treat skin conditions such as acne, eczema, and rashes. Some plants can be used for getting relief from stomach ulcers and food allergies, boost metabolism and fix appetite.

Plant fibres are used for manufacturing clothing materials such as jute, flax, and hemp.

What Are Plants?

Plants are photosynthetic eukaryotes that comprise all living organisms that are not animals. They include some fungi, algae, aquatic, and land species.

Important Characteristics Of Plants

The important characteristics of plants are:

• Photosynthesis –  It is the process they make their own food and survive.
• Cell walls    –  They descend from the green algae and are multicellular.
• Meristems   –  New tissues and organs are formed at the meristems.
• Hydrostatic Systems –  Plant cell walls are made of cellulose, and these species serve as hydrostatic systems.
• Reproduction –  Plants are capable of reproduction and can disperse new life through airborne spores.
• Stationary –  Plants cannot move and are bound static to the soil.
• Aesthetics –  Plants are pleasing to the eyes and provide humans with aesthetic pleasure. They can liven up indoor and outdoor environments.
• Life cycles- Each plant has its definite life cycle, and its growth or lifespan depends on environmental factors and nutrition.
• Protoplasm –  Protoplasm is the actual living matter present in plants.
• Adaptability –  Some plants are versatile and can adapt to harsh living conditions.

Significance And Benefits Of Plants

Following are different benefits, significance, and uses of plants:

•  Lower anxiety and stress – Indoor plants have reduced anxiety and stress. As per multiple studies, people exposed to the greenery around them performed better than those that didn’t.
• Improve indoor air quality – Plants scrub dust, contaminants, and pollutants from the air through phytoremediation. Several species, such as areca, spider plant, etc., have been helpful.
•  Alleviate allergies or asthma –  If you have any seasonal allergies or asthma, you may find that having various plants in your home can help alleviate them.
•  Boost oxygen levels  – Plants are good at filtering out carbon dioxide from the environment and boosting oxygen levels. They also remove unwanted chemicals from the air, thus making it easier to breathe.
•  Reduce global warming  – Plants help lower the global temperature of the atmosphere; without them, we wouldn’t be able to survive on this earth.
•  Prevent soil erosion  – Plants keep soils fertile worldwide and supply all the significant nutrients to them.
•  Enhance creativity – Plants can significantly improve creativity for those trying to exercise their imagination. Many artists, singers, musicians, and great people in history had plants in their homes.
• Absorb background noise  – If you live in a noisy environment, you’d be surprised to learn that plants can absorb background noise. The best way to reap this gift is by positioning them around the edges and corners of rooms, and some excellent examples are the Snake Plant and Weeping Fig.

Factors That Are Affecting Plants

The following are common factors that affect plants:

• Climactic Factors –  Plants are affected by climate conditions such as temperature, light, wind, humidity, and precipitation.
• Nutrition –  Plants absorb nutrients from the soil, and soil composition is essential for their growth and development.

Your child can learn a lot by writing an essay on plants. They will learn how nature works, where they get their food from, and why plants are vital to their lives.

Now that you know enough about plants, you can get to work on writing about them. Look up popular houseplants and study the varieties you like. That’s how you write a unique and creative essay that’s not only informational but a fun read!

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‘Plant Diversity’ topic of this year’s Plant Sciences Symposium

• by Alice Pierce and Matthew Davis
• April 10, 2024

This year, we are excited for the 2024 UC Davis Plant Sciences Symposium to represent work across the plant sciences with the theme, “Plant diversity from genes to ecosystems.”

The event is this Friday, April 11, in the Walter A. Buehler Alumni Center. Registration and coffee start at 8 a.m., with the event opening at 8:45 a.m. Jason Rauscher will speak; he’s the R&D academic relations lead for our event’s core partner Corteva Agriscience. The day includes speakers, poster sessions and networking.

Detailed schedule of events for the 2024 Plant Sciences Symposium

Learn more about our speakers here . 

As we prepared to bring the plant sciences community together for the annual symposium, we were struck by the diversity of research occurring across the field and wanted to find a way to showcase work from around the community. The symposium provides an amazing opportunity for attendees to interact with areas of science that they may not be familiar with, while still providing research presentations within their own fields.

This year, the symposium is aiming to encourage students, faculty, staff and industry professionals to synthesize across disciplines and network to form new and exciting collaborations. Our goal is for the 2024 UC Davis Plant Sciences Symposium to foster new connections to support interdisciplinary work in the plant sciences.

Corteva also will offer an informational session, called “Private Sector Careers in Agriculture,” from 3:30 to 4:30 p.m. Thursday, April 11, in PES 3001. It’s for anyone to learn more about career paths in the agricultural industry. Rauscher will be there, too.

Media Resources

• Trina Kleist, UC Davis Department of Plant Sciences, [email protected], (530) 754-6148 or (530) 601-6846

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