Educational Galaxy

Diversity in the Living World — EG's own notes, in simple words

Book: Curiosity (CBSE, Class 6)  |  Chapter 2  |  Medium: English

Diagram (labels are printed on the image): A herb, a shrub and a tree shown side by side for comparison of size and stem. A general teaching picture, not a book illustration.

Many different living things together — a picture of diversity in nature.

Diagram (labels are printed on the image): Leaf veins can form a net (reticulate venation) or run side by side (parallel venation). Roots can be a single main tap root with side branches, or many thin fibrous roots.

What the chapter is about

The living world is full of variety. Plants range from tiny herbs to giant trees, and animals range from tiny ants to huge elephants. Even within one kind there is variety — wheat, rice and many other grains are all different plants. This variety of living things is called diversity, and the variety in a place is its biodiversity.

With so many living things, study would be impossible without grouping. Classification means putting things into groups because they share a feature, and always naming the feature used. A group without a reason is just a list. One object can belong to different groups under different features: a mango tree is a tree by stem, and also a flowering plant by reproduction.

Plants are often grouped by their stems. Herbs are small plants with soft, green stems, such as wheat and tomato plants. Shrubs are medium-sized, with several woody stems branching near the ground, such as rose and lemon plants. Trees are tall, with one thick woody trunk, such as mango and neem trees. But stem alone is not enough: some plants, like creepers, need support, and climbers climb with tendrils.

Leaves also help us group plants. A leaf usually has a petiole (stalk), a broad flat lamina, and veins. The main vein in the middle is the midrib. In some leaves the veins form a net — reticulate venation, as in mango and peepal leaves. In others the veins run side by side — parallel venation, as in grass and banana leaves. There is a useful pattern: plants with reticulate venation usually have a tap root, while plants with parallel venation usually have fibrous roots.

Roots are of two main kinds. A tap root is one main root growing down, with smaller side roots — carrot and radish are tap roots we eat. Fibrous roots are a bunch of thin roots of nearly equal size, as in wheat and grass. Roots hold the plant in the soil and take in water and minerals.

Animals can be grouped in several ways: by habitat (land, water, or both), by how they move (walk, run, fly, swim, crawl), by what they eat (plants, other animals, or both), and by body features such as whether they have a backbone. Using more than one feature gives a clearer picture than using one alone.

Grouping helps in real life too. It makes study easier, helps us find useful plants and animals, and helps us protect the ones that are rare or in danger. When we know which group a plant or animal belongs to, we also know something about how it lives and what it needs.

Seeds add a third link to the pattern. A chickpea seed splits into two parts, each called a cotyledon, so chickpea is a dicotyledon (dicot). A maize seed has a single thin cotyledon, so maize is a monocotyledon (monocot). The rule is: dicot plants have reticulate venation and a tap root system, while monocot plants have parallel venation and fibrous roots. Wheat is a monocot (fibrous roots, parallel venation); kidney beans (rajma) are dicots (tap root, reticulate venation); radish, a tap root we eat, has reticulate venation in its leaves.

Surroundings shape animals too. Fishes live in water and have streamlined bodies and fins for moving in water; goats live in grassy areas and move with legs. Movement and body parts go together: ants walk on legs, pigeons walk and fly on legs and wings, fishes swim on fins. And diversity must be protected: the Silent Valley in Kerala, a moist evergreen forest rich in biodiversity, was saved when common people fought for ten years against a dam on the Kunthipuzha river, through awareness programmes, letters, seminars, petitions and court appeals. Cutting forests down to meet growing needs harms our surroundings in the same way — losing homes, soil and rainfall — and planting trees and protecting forests is how we answer it.

What you should learn

• Group plants as herb, shrub or tree by stem — and say which feature you used.
• Name leaf parts: petiole, lamina, midrib and veins; tell reticulate from parallel venation.
• Tell tap root from fibrous roots, and link each to its usual venation pattern.
• Group animals by habitat, movement and food — using more than one feature where possible.
• Explain why classification helps study, identification and protection of living things.

Chart / Table: Grouping plants by stem

Table: Grouping plants by stem

Table: Leaf veins and roots — the usual pairing

Table: Grouping animals three ways

Table: Dicots and monocots — seed, leaf and root together

Practice set — try it yourself

1. What is meant by diversity in the living world?
   Hint: Think about variety, not just number.
2. Give one example each of a herb, a shrub and a tree.
   Hint: Think about stem type for each.
3. Why do scientists group living things?
   Hint: Think about study and protection.
4. A plant is 2 metres tall but has a soft green stem. Is it a tree? Why or why not?
   Hint: Think about which feature decides the group.
5. Name two different habitats and one animal found in each.
   Hint: Think about land and water habitats.

Questions with Answers

1. What is biodiversity?
   Biodiversity is the variety of living things — plants, animals and micro-organisms — found in an area. It includes differences between species and differences within a species.
2. How are plants grouped into herbs, shrubs and trees?
   Plants are grouped by their stem and size. Herbs are small plants with soft, green stems. Shrubs are medium-sized plants with many woody stems branching near the ground. Trees are tall plants with a single thick woody trunk.
3. Why is grouping of living things useful?
   Grouping makes the study of millions of living things manageable. It helps us identify organisms, understand their relationships, find useful species, and plan protection for rare ones.
4. A student groups a rose plant as a tree because it is tall. Is this correct? Give a reason.
   No, it is not correct. A rose is a shrub because it has many woody stems branching near the ground, and grouping is based on stem type, not height alone.
5. Why should we protect biodiversity?
   Every living thing plays a role in nature — plants give oxygen and food, animals help pollination and seed spread, and micro-organisms enrich soil. Losing species disturbs these links and harms the balance of nature.

More NCERT-exercise questions — extra practice

1. What is meant by classification? Why do we classify living things?
   Classification is arranging things into groups on the basis of a common feature. We classify because there are so many living things that study, identification and protection would be impossible without groups.
2. Fill in the blank: The stalk that joins a leaf to the stem is called the __________.
   Petiole.
3. True or False: All plants with parallel venation have a tap root. Correct the statement if false.
   False. Plants with parallel venation usually have fibrous roots; plants with reticulate venation usually have tap roots.
4. A plant has a soft, green stem and grows close to the ground. Is it a herb, a shrub or a tree? Give the reason.
   A herb, because herbs are small plants with soft, green stems, while shrubs have woody stems and trees have a thick woody trunk.
5. Name the two main kinds of roots. Give one example of each that we eat.
   Tap root — carrot or radish. Fibrous roots — wheat is the usual example of a plant with fibrous roots (its grain is eaten); onion also grows with fibrous roots.
6. Group these animals by habitat: fish, lion, frog. What feature did you use?
   By habitat: fish — water; lion — land; frog — both land and water. The feature used is habitat, the place where the animal lives.
7. Why is it wrong to group mango and rose together just because both have flowers?
   Because grouping must follow one stated feature. By stem, mango is a tree and rose is a shrub, so they belong to different stem groups even though both flower.
8. What are the parts of a leaf? Which part carries water and food materials through the leaf?
   A leaf has a petiole, a lamina and veins, with the midrib as the main vein. The veins carry water into the leaf and food materials away from it.
9. Give one way in which grouping helps protect living things.
   Grouping shows which plants or animals are rare or in danger and what kind of habitat they need, so protection can be planned for that group and its home.
10. Two seeds are given: wheat and kidney beans. What differences would you find in the roots and leaf venation of their plants?
    Wheat is a monocot: its plants have fibrous roots and parallel venation. Kidney beans are dicots: their plants have a tap root and reticulate venation.
11. A radish is dug out of the soil. What type of root is it, and what venation would its leaves show?
    Radish is a tap root — one main root growing downwards. Its leaves would show reticulate venation, because dicot plants with tap roots have net-like veins.
12. Group these animals by habitat into aquatic (A), both land and water (C), and terrestrial (B): horse, dolphin, frog, sheep, crocodile, squirrel, whale, earthworm, pigeon, tortoise.
    A (aquatic): dolphin, whale. C (both): frog, crocodile, tortoise. B (terrestrial): horse, sheep, squirrel, earthworm, pigeon.
13. Raj says a hibiscus (gudhal) plant is a shrub. What questions could his friend ask to check this claim?
    Is the stem woody or soft and green? Do the branches arise close to the ground or higher up the stem? How tall is it — short, medium or tall? A shrub has several woody stems branching near the ground and medium height, like rose; a herb would have a soft green stem.
14. What other similarities do dicot plants share with each other, and monocot plants with each other?
    Dicots share two cotyledons in the seed, reticulate venation and a tap root system (e.g. chickpea, kidney bean). Monocots share one thin cotyledon, parallel venation and fibrous roots (e.g. wheat, maize).
15. A duck has webbed feet, while a pigeon does not. What difference does this make, and which activity can the duck perform with them?
    Webbed feet work like paddles: the skin between the toes pushes against water, so the duck can swim well. The pigeon, with separate toes, walks and flies but does not swim like a duck.
16. Compare a mountain goat with a goat found in the plains. Why do they differ?
    They differ because their surroundings differ. The mountain goat's body suits cold, steep, rocky ground, while the plains goat's body suits grassy flat land. Body features follow the habitat the animal lives in.
17. As population grows, forests are cut down for comfort and needs. How can this affect our surroundings, and how can we address it?
    Cutting forests destroys animal homes, exposes soil to erosion, changes rainfall and harms biodiversity, as the Silent Valley story shows in reverse — people saved a forest by awareness, petitions and court appeals. We address it by planting trees, protecting forests, and using resources carefully instead of clearing more forest.

How to use this page: Read the summary, say the Key Terms in your own words, then try the practice set without looking. Use the Questions with Answers to check yourself afterwards. Ask your teacher or parent to check your answers.