Diversity in the Living World

After a refreshing rain, the science teacher Madam Sulekha invites Dr Raghu (a scientist at a nearby Research Laboratory) and Maniram chacha (an elderly person from a nearby community, expert at mimicking bird calls and identifying plants and animals) to lead a nature walk.

• Objective: to experience the beauty and variety of plants and animals in nature. Students carry a notebook, a pen and a water bottle.
• Dr Raghu: notice the variety of smells; respect all living creatures and observe them without disturbing.
• Maniram chacha: not only observe but also listen carefully to different sounds.
• Students see grasses, bushes, large trees, birds, butterflies moving flower to flower, monkeys jumping between trees.
• Each bird has a unique chirp — an example of diversity in nature.

Plants show a variety of features: tall/short, hard/soft stems; different shapes of leaves and their arrangement; flowers varying in colour, shape and scent.

Animals differ in where they live, what they eat and how they move. Some live on land, some on trees (birds), fish in water, and frogs on land as well as in water.

The variety of plants and animals found in a particular region contributes to the biodiversity of that region. Each member has a different role — trees give food and shelter to birds and other animals; animals spread seeds after eating fruits. So plants and animals are dependent on each other.

Just as arranging books in groups organises a school bag, we can group living things by similarities and differences. Different students may choose different bases — height of plants, presence/absence of flowers, hard/soft stem; for animals, what they eat, where they live, colour, how they move (Fig. 2.2).

Climbers: weak stems that need support to climb and grow. Creepers: creep along the ground.

The thin lines on a leaf are veins; their pattern is venation.

• Reticulate venation: a net-like pattern on both sides of a thick middle vein — e.g. hibiscus.
• Parallel venation: veins run parallel — e.g. banana and grasses.

• Taproot: one main root with small side roots arising from it — e.g. mustard, hibiscus.
• Fibrous roots: a bunch of similar-sized thin roots arising from the base of the stem — e.g. common grass.

Activity 2.6 reminds us to replant the herbs after observing their roots.

Generally, plants with reticulate venation have taproots, while those with parallel venation have fibrous roots. (Sadabahar: taproot + reticulate. Lemongrass: fibrous + parallel. Chickpea: taproot + reticulate. Wheat: fibrous + parallel.)

Seeds: a soaked chickpea splits into two parts — each part is a cotyledon. Plants with two cotyledons are dicotyledons (dicots). Maize has a single thin cotyledon — a monocotyledon (monocot).

Animals can fly, run, crawl, walk, hop or jump, using different body parts — wings, legs, fins and so on.

Animals also differ in shape, size, structure and colour — these too can be used for grouping.

Fish live in water and have streamlined bodies and fins; goats live in grassy areas and move with legs.

• Cactus (deserts of Rajasthan, seen by Alex): thick, fleshy stems store water to tolerate heat. Hot deserts are very hot by day and very cold at night, with little water.
• Deodar (Himalayas of Himachal Pradesh, seen by Maya): conical shape, flexible sloping branches let snow slide off easily.
• Rhododendron: in the Shola forests of the Nilgiris they are shorter with smaller leaves to survive heavy winds on mountain tops; in Sikkim (Pema) they are taller. The same plant shows different features in different regions.
• Sea: Sagar saw huge whales and colourful fish in the Andaman and Nicobar Islands — a streamlined body helps fish swim.

Biodiversity varies from region to region because of diverse conditions.

Kashi from Rajasthan adds: camels excrete small amounts of urine, have dry dung and do not sweat — so they lose little water and can survive for many days without drinking water.

The special features that enable plants and animals to survive in a particular region are called adaptations. E.g. the shape of the deodar and the height of the rhododendron.

The place where plants and animals live is called their habitat. Sea turtle → sea/ocean; camel → hot or cold desert; rhododendron → mountains. A habitat provides food, water, air, shelter and other needs; many living things can share one habitat. Habitat shapes the biodiversity of a region.

• Terrestrial (land): forests, deserts, grasslands, mountains.
• Aquatic (water): ponds, lakes, rivers, oceans.
• Amphibians (e.g. frogs) live in water as well as on land.

When habitats are damaged, plants and animals lose their homes, food and other resources — leading to loss of biodiversity.

• The Bengal Tiger, Cheetah and Great Indian Bustard have declined due to habitat loss caused by human activities.
• Project Tiger — started 1973 to protect the Bengal Tiger.
• Cheetah Reintroduction Project — started 2022.
• Great Indian Bustard habitats declared Protected Areas in Gujarat, Rajasthan and Maharashtra.
• Sacred groves — undisturbed forest patches all over India, protected by local communities; home to many medicinal plants — "a community protected treasure of biodiversity".

Janaki Ammal (1897–1984) — Indian botanist who documented and preserved India's plant biodiversity; played a key role in the 'Save Silent Valley' movement; as head of the Botanical Survey of India, she started programmes to document India's plant diversity.

Salim Ali (1896–1987) — the 'Birdman of India'. Travelled across India observing birds, listing them and documenting their travel routes and habitats; helped preserve Keoladeo National Park (Bharatpur, Rajasthan) and Ranganathittu Bird Sanctuary (Mandya, Karnataka); wrote a landmark series of 10 books on birds of the Indian Subcontinent; awarded the Padma Vibhushan in 1976.

Plan a nature walk; observe plants, insects, birds and other animals, and the weather. Collect fallen leaves/flowers for a scrapbook — but do not pluck or disturb. Record stems, leaves and flowers in Table 2.1 (e.g. grass: soft, thin stem, single leaves growing alternately; tulsi: hard, thin stem, pairs of opposite leaves, pinkish-purple flowers; hibiscus: hard stem; neem: hard, thick stem, smooth leaves). Record animals' homes, food and movement in Table 2.2 (crow: tree, insects, flies and walks; ant: nest in soil, leaves/seeds/insects, six legs; cow: grass and leaves).

Close your eyes for 30 seconds, think of a plant and an animal you have appreciated, and draw them on the blackboard. Count how many different ones the whole class drew — and realise there are many more varieties: biodiversity.

In groups of 5–6, paste pictures of plants and animals on cards, then group them by common features and compare the basis of grouping with other groups. Different groups choose different bases.

Observe plant height (shorter/as tall as/taller than you), stem colour, bendability, thickness, and where branches arise. Fill Table 2.3: mango — tall, brown, hard, thick, branches high → tree; rose — medium, brown, hard, thin, branches near ground → shrub; tomato — short, green, tender, thin → herb.

Compare the shape and veins of collected leaves: hibiscus (reticulate) vs banana and grass (parallel).

Use a khurpi (trowel) to dig out small herbs without damaging roots (wet the soil first), wash and observe the roots, then replant them. Compare the mustard (taproot) and grass (fibrous) root systems.

Before planting saplings (lemongrass, marigold, sadabahar…), record leaf venation and root type in Table 2.4. Lemongrass: parallel + fibrous. Sadabahar: reticulate + taproot. Conclusion: generally reticulate ↔ taproot, parallel ↔ fibrous.

Soak chickpea and maize seeds for two or three days; remove the chickpea seed coat. Chickpea splits into two cotyledons (dicot); maize has one thin cotyledon (monocot).

Make a poster of animals (Fig. 2.7) and list in Table 2.5 how each moves and which body parts it uses.

Recreate Table 2.6 on the blackboard: desert — camel; mountains — deodar tree; ocean — fish; forest — lion. Add more. The plants and animals of one region differ from those of another.

(a) Grass, (b) Tulsi (Holy Basil), (c) Hibiscus (Gudhal) — showing different stems, leaf arrangements and flowers.

Four bases for grouping: presence/absence of flowers, hard/soft stem, eating habits, and the place they live.

(a) Tree (mango), (b) Shrub (rose), (c) Herb (tomato).

(a) Hibiscus leaf with reticulate venation; (b) banana leaf and (c) grass leaf with parallel venation.

(a) Taproot system in a mustard plant — one thick main root with side roots; (b) fibrous root system in common grass — a bunch of thin roots from the stem base.

(a) Chickpea (dicot) opened into two cotyledons; (b) maize (monocot) with a single cotyledon.

A collage of animals that move in different ways — flying, walking, crawling, swimming, hopping.

(a) A fish swims with fins; (b) a goat walks on the ground with legs.

A cactus with thick, fleshy stems in a desert; a conical deodar tree with sloping branches in the mountains.

A tall, long-legged, one-humped camel with wide hooves in the hot desert of Rajasthan; a shorter, two-humped, long-haired camel in the cold desert of Ladakh.

(a) A short rhododendron with small leaves in the Nilgiris; (b) a taller rhododendron in Sikkim.

Photographs of the Bengal Tiger, Cheetah and Great Indian Bustard; and a sacred grove in the Western Ghats.

1. Two types of seeds — (a) wheat, (b) kidney beans. What differences do you find in the roots and leaf venation of their plants?
2. Group these animals by habitat — aquatic (A), terrestrial (B), both (C): horse, dolphin, frog, sheep, crocodile, squirrel, whale, earthworm, pigeon, tortoise.
3. Manu's mother says radish is a kind of root. What type of root is it? What venation would its leaves have?
4. Compare a mountain goat with a goat of the plains. Similarities, differences, and reasons for the differences?
5. Group cow, cockroach, pigeon, bat, tortoise, whale, fish, grasshopper and lizard into two groups using a feature not discussed in the chapter.
6. Forests are being cut down as population grows. How can this affect our surroundings? How can we address this challenge?
7. Analyse the flowchart (Plant → Does it have leaves? → Does it have reticulate venation? → A / B). Give examples of A and B.
8. Raj says "Gudhal (hibiscus) is a shrub." What questions can Sanjay ask for clarification?
9. Table: Group A — dicot, taproot; Group B — monocot, fibrous roots. Give examples. (a) What other similarity do group A plants have? (b) Group B?
10. Compare the webbed feet of a duck with a pigeon's feet. What activity can the duck perform with them?

Worked answers to the textbook questions are in the Question Bank (section G).

1. Have you ever observed different plants and animals around you? Share your observations.
2. What similarities and differences did you find among the plants (Table 2.1) and animals (Table 2.2) you observed?
3. Can you think of more examples showing plants and animals depend on each other?
4. What is the importance of grouping?
5. How can you group plants as herbs, shrubs and trees using Table 2.3?
6. Can plants be grouped on the basis of leaf venation?
7. Is there any relation between leaf venation and root type of the same plant?
8. Is there any relation among seed type, root type and leaf venation?
9. How can we group animals based on their movements?
10. Why does the biodiversity of one region vary from another? What advantages do the two camels' differences give them?
11. What would happen if the habitat of a plant or animal is damaged? Can a fish survive without water?

• Read about an Indian scientist or wildlife biologist working to protect India's biodiversity; prepare a brief report.
• Explore the contributions of Divya Mudappa, Usha Lachunga, Ghazala Shahabuddin, Nandini Velho, Vidya Athreya, Uma Ramakrishnan and Divya Karnad; report on any three.
• Label school plants with local names; list them.
• Plan a field visit and prepare a class biodiversity register.
• Find out about Project Tiger and similar projects; prepare a presentation.
• Group discussion: how can we protect biodiversity around us? Prepare a group-wise report.
• Ask elders which plants and animals they see now but did not earlier (and vice versa); make a scrapbook.