Diversity in the Living World
Class 6 Science — Quick Revision Chapter Notes
1. Introduction
Imagine walking through a park on a bright, sunny morning. You hear birds chirping, see butterflies fluttering over colourful flowers, and notice trees of all shapes and sizes standing tall around you.
Have you ever wondered why each tree looks different?
Why do birds have unique chirps?
Or how some animals live on land while others thrive in water?
The world around us is full of fascinating plants and animals, each playing its part in making nature vibrant and alive. In this chapter, we will explore the variety of life around us, known as biodiversity. We will learn how plants and animals are suited to their surroundings, how they depend on one another, and why it is important to protect the diversity of life on our planet.
2. Diversity in Plants and Animals Around Us
Diversity means the variety of plants and animals found in a particular region. We can observe and compare plants and animals based on their similarities and differences.
Diversity in Plants
Plants can be different from one another in their size, shape, colour, stems, leaves, flowers, roots and the way they grow. The following features help us observe and compare plants.
1. How do plants differ in height?
Plants may have different heights. Examples of plant heights:
Tall: Some plants, such as mango trees, grow very tall and have a strong, thick trunk.
Short: Other plants, such as rose bushes, are much shorter and remain close to the ground.
2. What do the stems of plants look like?
The stem usually grows above the ground. It makes the main structural framework of the plant. The stem bears leaves, branches, buds, flowers and fruits.
Types of stems:
Hard: Plants such as the banyan tree have hard, woody stems that provide strong support.
Soft: Smaller plants such as mint have soft, green stems that are flexible and less strong than woody stems.
3. What are some common shapes of leaves that you can see in different plants?
The leaf is a thin, flat and green structure that arises from a node of the stem.
Shape: Leaves have different shapes and sizes. For example, banana leaves are broad and large.
Arrangement: Leaves may be arranged in different patterns on a stem. For example, a pair of leaves of tulsi is arranged opposite each other on a branch.
Venation: The arrangement of veins in a leaf is called venation.
Reticulate venation: The veins form a network. It is common in dicot plants such as hibiscus and peepal.
Parallel venation: The veins run parallel to one another. It is common in monocot plants such as grass and wheat.
4. What different colours can you see in the flowers around you?
Flowers may differ in colour, shape and scent.
Colour: Flowers have different colours, such as the bright red colour of a hibiscus flower.
Scent: Flowers may have different scents.
Diversity in Animals
Animals around us show great variety in their size, shape, habitat, food habits and movements. The following features help us compare animals.
1. Where does the animal live?
A habitat is the place where a plant or animal lives.
Examples of habitats:
Land: Cows, lions and squirrels live on land.
Water: Fish and turtles live in water.
Both land and water: Frogs can live on land as well as in water. Frogs are amphibians.
2. What kind of food does the animal eat?
Animals consume a variety of foods depending on their diet and species.
3. How does the animal move?
Animals use different body parts to move, depending on their kind and surroundings.
Walking: Cats and dogs use their legs to walk or run.
Crawling: Animals such as snakes crawl.
Hopping / Jumping: Frogs and rabbits primarily use their legs to hop or jump.
3. What is Biodiversity?
Biodiversity refers to the variety of plants and animals found in a particular region. Plants and animals depend on one another.
4. How to Group Plants and Animals?
Can you find a group of plants or animals that have something in common? For example, do any of them have similar colours, shapes or sizes?
Grouping plants and animals makes it easier to study and understand their great diversity by comparing their similarities and differences.
How to Group Plants
Grouping plants helps us understand their characteristics and place them into groups based on common features.
Based on Height, Stems and Branching
Trees are plants that grow very tall and have hard, thick, brown and woody stems. Their branches usually begin higher up on the stem, away from the ground. Examples: Mango, banyan, acacia, coconut, poplar and willow.
Shrubs are plants that are shorter than trees. They have many brown, woody stems that begin branching close to the ground. Their stems are hard but generally not as thick as the stems of trees. Examples: Lemon, henna and rose.
Herbs are usually small plants with soft, green stems. Examples: Wheat, paddy, cabbage, grass and coriander. The tomato plant is also a herb.
Climbers have very thin, long and weak stems that cannot stand upright. They use external support to grow upwards. Examples: Pea plant, grapevine, sweet gourd, money plant, jasmine, runner beans and green peas.
Creepers grow along the ground. They have fragile, long and thin stems that can neither stand erect nor support their entire weight. Examples: Watermelon, strawberry, pumpkin and sweet potato.
Based on Leaves
Leaves can have different shapes and sizes. For example, the broad leaves of a mango tree are different from the thin leaves of grass. The pattern of the veins in a leaf is called venation.
Parallel venation: In some leaves, the veins run parallel to one another. Banana and grasses are examples.
Reticulate venation: In some leaves, the veins form a net-like pattern. Hibiscus is an example.
Note: Generally, plants with reticulate venation tend to have taproots, while plants with parallel venation tend to have fibrous roots. However, there are exceptions. Chickpea, like most dicots, has taproots and reticulate venation. Wheat has fibrous roots and parallel venation.
Based on Roots
Roots are the parts of a plant that usually grow underground and help the plant remain anchored in the soil. There are two main types of roots:
Taproots: A taproot system has one main root that grows from the base of the stem. Many smaller roots and branches arise from the main root. Examples: Pea, radish, carrot, mango, marigold and mustard.
Fibrous roots: A cluster of thin, fibre-like roots arises from the base of the stem. These roots spread through the soil. Examples: Maize, grass, wheat and millet.
Based on Seeds
Seeds are the parts of a plant that can grow into new plants. There are two main types of seeds based on the number of cotyledons, which are the first leaves present in a seed:
Dicotyledons (dicots): These plants have seeds with two cotyledons that can usually be split into two parts. Chickpea is an example of a dicot seed. Plants with dicot seeds usually have reticulate venation and a taproot system.
Monocotyledons (monocots): These plants have seeds with a single cotyledon. Maize is an example of a monocot seed. Plants with monocot seeds typically have parallel venation and a fibrous root system.
How to Group Animals
Animals differ in shape, size, structure, colour and other features. These features can be used to group animals, and grouping helps us understand their diversity.
Based on movement:
Running or walking: Animals that use their legs to run or walk on the ground, such as dogs and horses.
Crawling: Animals that move by crawling on their bodies, such as snakes.
Hopping or jumping: Animals that hop or jump using their legs, such as frogs and rabbits.
5. Plants and Animals in Different Surroundings
Plants and animals live in different places such as deserts, mountains, oceans and forests. Each has special features that help it survive in its surroundings. For example, camels have features that help them live in deserts, while fish have fins that help them swim in water. These special features are called adaptations.
In the Desert
Plant Adaptation: Cactus plants have thick and fleshy stems that store water. This helps them survive in hot and dry conditions.
Animal Adaptation: Camels of hot deserts have long legs and wide hooves that help them walk on sandy ground without sinking. Hot-desert camels have one hump, while cold-desert camels have two humps. Cold-desert camels also grow long hair from head to neck to survive the cold winters. Camels excrete small amounts of urine, have dry dung and sweat very little, so they lose little water.
On Mountains
Plant Adaptation: Deodar trees have a conical shape and sloping branches. This allows snow to slide off easily and helps the trees survive in cold, snowy regions.
Animal Adaptation: Mountain goats are found in mountainous regions with strong hooves for climbing.
In the Ocean
Aquatic Life: Oceans are aquatic habitats with many plants and animals. Fish have streamlined bodies and fins that help them move easily through water.
In the Forest
Forest Habitats: Forests have many kinds of plants and trees. Lion is an example of an animal found in forests.
Rhododendron
Rhododendrons are found in different regions and may show different features depending on the conditions of those regions:
In the Shola forests of the Nilgiris, rhododendrons are shorter and have smaller leaves to survive the heavy winds on mountain tops.
Rhododendrons observed in the mountains of Sikkim are taller.
Adaptations and Habitats
Adaptations are the special features that enable plants and animals to survive in a particular region.
Deserts: Camels have long legs and humps that help them survive in deserts. They store fat in their humps.
Oceans: Fish have streamlined bodies and fins that help them move easily through water.
Desert Flora: Cacti have thick and fleshy stems that store water.
A habitat is the place where a plant or animal lives. It provides food, water, air, shelter and other necessary conditions for survival.
Terrestrial habitats: Habitats on land, such as forests, deserts, grasslands and mountains.
Aquatic habitats: Habitats in water, such as ponds, lakes, rivers and oceans. Frogs can live on land as well as in water and are called amphibians.
6. Protecting Biodiversity
Talk to parents, grandparents and neighbours to learn about plants, birds, insects or animals that they saw frequently during their childhood but that have become rare now.
Such changes often happen because of habitat destruction, which leads to:
Loss of homes, food and other resources for plants and animals.
A decline in biodiversity.
Examples of Declining Populations
Bengal tiger: Its population has been reduced in many areas because of habitat loss and other human activities.
Cheetah: Cheetahs lost their natural habitat in India. Reintroduction efforts began in 2022 under the Cheetah Reintroduction Project.
Great Indian bustard: Its population declined due to habitat loss. Its habitats in Gujarat, Rajasthan and Maharashtra have been declared protected areas.
Government Initiatives for Conservation
Project Tiger (1973): This project was started to protect the Bengal tiger and its habitat.
Cheetah Reintroduction Project (2022): This project aims to restore the cheetah population in India.
Protected Areas: Important habitats for the Great Indian bustard and other wildlife have been protected in different regions and states.
Sacred Groves
Definition: Sacred groves are patches of forest protected by local communities. They conserve many plants, animals and medicinal plants.
Features: Sacred groves are home to rich biodiversity. No one is allowed to harm animals, cut trees or disturb these areas.
Importance: Sacred groves help preserve biodiversity and protect natural habitats.
7. Chapter Summary
Plants and animals show variety in their features, habitats, food and movements.
Grouping arranges things into groups based on common features and makes study easier.
Plants can be grouped as herbs, shrubs and trees based on height, stem and branching, and also using venation, roots and cotyledons.
Dicots generally have reticulate venation and taproots, while monocots generally have parallel venation and fibrous roots.
Biodiversity varies from region to region because of different environmental conditions.
Adaptations help plants and animals survive in particular regions.
Habitats can be grouped as terrestrial and aquatic. Frogs can live in both and are amphibians.
Damage to habitats causes loss of homes, food and other resources and leads to loss of biodiversity.
We must protect biodiversity to help plants and animals survive and thrive.
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