12 min readConcept sheetSection A MCQ (1 mark) and objective (2 marks, true or false or fill in the blanks); Section B very short answer (2 marks) or short answer (3 marks)

Adaptations to water, land, desert, cold and air

Adaptations are special features that suit a living thing to its habitat, such as fleshy stems in cacti, webbed feet in ducks and hollow bones in birds.

AdaptationA special feature that suits a plant or animal to life in its own habitat (the place where it lives)

HydrophytesWater plants (hydro = water, phyte = plant), e.g. Hydrilla, Vallisneria, lotus, water lily, Pistia, water hyacinth

MesophytesLand plants of places neither very dry nor very wet (meso = moderate); most land plants

XerophytesDesert plants (xero = dry) that store and save water, e.g. cacti

Adaptations in plants

Plant group	Key adaptations	Examples
Hydrophytes (water)	Reduced roots, as water is all around. Floating leaves have stomata only on the upper surface; submerged leaves have none. Thin, narrow or ribbon-shaped leaves resist water currents. Long, slender, spongy stems. Broad floating leaves with a waxy upper surface that repels water	Hydrilla (thin narrow leaves), Vallisneria (ribbon leaves), lotus and water lily (waxy floating leaves), Pistia, water hyacinth
Mesophytes (moderate land)	Need a steady water supply. Large, thin, broad leaves with many stomata on the underside. Well-developed, branched roots with a root cap. A well-organised shoot	Most garden and crop plants, such as mango, wheat and rose
Xerophytes (desert)	Fleshy (succulent) stems or leaves that store water. Few or no leaves, to cut transpiration. Fewer stomata. Thorns for protection. Deep, widespread roots to collect water	Cacti, Casuarina

Adaptations in animals

Habitat	Key adaptations	Examples
Water	Streamlined body (pointed at both ends) to cut friction; smooth, almost hairless skin in water mammals; fins to swim, steer and balance; flippers; webbed feet as paddles; flat tail as an oar; gills for breathing; swim bladder filled with air for floating; blubber (thick fat) for warmth; eyes and nostrils on top of the head; transparent eyelids	Fish, whale, dolphin, duck, crane (long legs and neck for wading), prawn
Desert	Stay in burrows by day and come out at night; long body parts to lose heat; scaly skin that resists drying; camel's hump stores fat; camels drink a lot at once, go long without water and pass concentrated urine; reptiles pass urine as insoluble uric acid to save water	Camel, desert lizards and snakes
Cold	Very thick fur that traps air; a layer of fat under the skin; round, bulky body with short legs, ears and tail to save heat; dense feathers in penguins	Polar bear, penguin
Air	Streamlined body; forelimbs turned into wings (feathers in birds, a skin fold between the fingers in bats); hollow, light bones; strong flight muscles	Birds, bats (true fliers)

Why living things adapt

Adaptations help living things to compete for food, defend themselves, find good conditions to reproduce and respond to changes around them. A frog shows two sets at once: strong legs to jump on land and webbed feet to swim. Some animals live on trees and come down, or glide, only for short trips. They are arboreal (tree-dwelling): the flying squirrel, flying lizard, tree frogs, lemurs and monkeys. The true aerial animals are birds and bats.

Hydrophyte vs xerophyte

Hydrophyte (too much water)Small roots, thin or ribbon leaves, spongy stems, stomata on the upper side or none. The plant does not need to save water.

Xerophyte (too little water)Deep, wide roots, few or no leaves, fleshy water-storing parts, few stomata. Every feature saves water.

Activity: study the adaptations of two animals (practical)

Choose any two of cockroach, fish, frog, lizard and pigeon. Here, a fish and a pigeon.

1
Look at each specimen from all sides. Note its body shape: both the fish and the pigeon are streamlined, which cuts friction in water and in air.
2
Note the organs for moving: the fish has fins and a tail; the pigeon has wings covered with feathers and clawed feet for perching.
3
Note the body covering: the fish has slippery scales; the pigeon has feathers that keep it warm and help it fly.
4
Note the breathing organs: the fish has gills under covers on each side of the head; the pigeon breathes air through nostrils on its beak.
5
Record each feature and the habitat it suits in a table, and draw a neat labelled diagram of each animal.
6★
Conclusion: each body feature suits the medium the animal lives and moves in.

★ key step

Activity: visit a pond and list its plants

1
Visit a nearby pond or lake and look at the plants in and around it. Find out their common and scientific names if you can.
2
List the plants floating freely on the water, such as Pistia and water hyacinth.
3
List the plants that stay on the surface but have roots or stems in the water, such as lotus and water lily. Also list any fully under water, such as Hydrilla.
4
For each, note the features that help it: waxy upper leaf surface, broad flat leaves, spongy stem, ribbon-like leaves.
5★
Conclusion: pond plants have reduced roots, light spongy parts and waxy floating leaves that suit life in water.

★ key step

In real life

In the Thar desert, camels carry goods and people because they can go a long time without water. The lotus, India's national flower, keeps its broad leaves dry on the pond surface thanks to their waxy coat.

Exam angle

1 marks: “Name one water plant whose long, ribbon-shaped leaves protect it from water currents.” Vallisneria.

2 marks: “A cactus has spines in place of broad leaves and a thick, fleshy stem. Explain how each of these features helps it survive in a desert.” Spines instead of leaves: fewer stomata and less transpiration, so less water is lost; they also protect the plant from animals. Fleshy (succulent) stem: stores water for dry periods.

3 marks: “Compare the adaptations of a fish and a bird to the medium they move in. Give three points.” Both streamlined. Fish: fins, gills, swim bladder, scales. Bird: wings with feathers, hollow light bones, strong flight muscles.

Remember it

Hydro = water, Meso = middle, Xero = dry. Water plants let go of water-saving; desert plants hold on to every drop.