1. The Living World: Adaptations and Classification
Complete solutions to the Exercises. Maharashtra State Board (Balbharati), Grade Seven General Science.
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Exercises
| ‘A’ Group | ‘B’ Group |
|---|---|
| (1) Lotus | (d) Adapted to live in water |
| (2) Aloe | (c) Adapted to live in deserts |
| (3) Cuscuta | (b) Haustorial roots for absorption of food |
| (4) Venus flytrap | (a) Flower and leaves attract insects |
I am a penguin. I live in polar region covered by snow. My abdomen is white. My skin is thick with a layer of fat underneath. My body is spindle-shaped. My wings are small. My toes are webbed. We live in flocks.
(a) Why is my skin white and thick and why is there a thick layer of fat underneath?
- The white colour merges with the snow. So enemies cannot see the penguin easily.
- The thick skin prevents loss of body heat.
- The thick layer of fat protects the body from extreme cold. It keeps the body warm.
(b) Why do we live in flocks sticking close to each other?
The polar region is extremely cold. Penguins stand close to each other in flocks. This keeps them warm. A flock also gives protection from enemies.
(c) Which geographical region do I inhabit? Why?
The penguin lives in the polar region (Antarctica). This region is covered with snow throughout the year. The penguin’s body is adapted to this very cold climate. The sea around gives it plenty of fish as food.
(d) Which adaptations should you have to enable you to live permanently in the polar region? Why?
- Thick skin and a thick layer of fat below the skin – to protect the body from cold.
- White colour – to merge with the snow and hide from enemies.
- Spindle-shaped body, webbed toes and small wings – to swim in water.
- Living in groups – to keep warm and stay safe.
These adaptations are needed to survive in the extreme cold.
(a) Cockroach – I have five legs.
The cockroach is lying. A cockroach is an insect. Insects have six legs.
(b) Hen – My toes are webbed.
The hen is lying. A hen lives on land. Its toes are separate with claws. Webbed toes are found in water birds like the duck.
(c) Cactus – My fleshy, green part is a leaf.
The cactus is lying. The fleshy green part of a cactus is its stem. Its leaves are modified into thorns.
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(a) There is extreme heat in deserts.
Deserts are very hot and water is scarce. Desert plants like cactus have thorns instead of leaves. This reduces the loss of water. Their stem is thick and fleshy. It stores water and food. The green stem carries out photosynthesis. The roots go deep into the soil in search of water. Desert animals have thick skin. The camel has long legs and flat, cushioned soles. Rats, snakes and lizards live in deep burrows during the day.
(b) Grasslands are lush green.
Grasslands have many types of grasses and bushes. Herbivores like deer, rabbit and blackbuck live here. Their eyes are on the sides of the head. So they can see all around. They have long legs to run fast. Their colour merges with the grass. Carnivores like the tiger hide in tall grass. They have strong legs, padded paws, sharp claws and pointed teeth.
(c) Insects are found in large numbers.
Insects are found almost everywhere. Their body is light. They have two pairs of wings and three pairs of legs. Many insects have colours that merge with leaves and flowers. This protects them from enemies. Many animals feed on insects. The frog and the chameleon have long, sticky tongues to catch them. Plants like the Venus flytrap, drosera and pitcher plant trap insects to get nitrogen.
(d) We hide.
Many animals hide to protect themselves. Their colour merges with the surroundings. This is called camouflage. Butterflies, lizards and grasshoppers merge with leaves and flowers. Deer merge with dry grass. The polar bear has white fur that merges with snow. Desert animals hide in burrows during the day. The tiger hides in tall grass to catch its prey.
(e) We have long ears.
Herbivores like deer, rabbit and blackbuck have long ears. Their ears can move in different directions. They can hear even faint sounds from far away. So they get a warning when a predator comes near. Then they run away quickly. Thus, long ears protect them from enemies.
(a) Why is the camel called the ‘Ship of the desert’?
A ship carries people and goods across the sea. In the same way, the camel carries people and goods across the desert. It is well adapted to desert life:
- It has long legs with flat, cushioned soles. They do not sink in the sand.
- It can live without water for many days.
- Its hump stores fat. This gives energy when food is not available.
- Its thick skin prevents loss of water.
- Folds of skin on the nostrils and long eyelashes keep out sand.
Hence, the camel is called the ‘Ship of the desert’.
The camel’s hump stores fat, not water.
(b) How can the plants like cactus and acacia live in deserts with scarce water?
- Their leaves are modified into thorns or are very small. So less water is lost.
- The stem of cactus is thick and fleshy. It stores water.
- The stem is green. It carries out photosynthesis.
- A waxy layer on the stem prevents loss of water.
- Their roots go deep into the soil to get water.
(c) What is the inter-relationship between adaptations of organisms and their surroundings?
Every surrounding has its own conditions of temperature, water and food. Organisms develop adaptations to suit these conditions. For example, the lotus has waxy leaves to live in water. The cactus has thorns to live in the desert. The polar bear has thick fur to live in snowy regions. Thus, adaptations depend on the surroundings. Organisms that cannot adapt cannot survive there.
(d) How are organisms classified?
Organisms are classified into groups and sub-groups. This is done on the basis of their similarities and differences. This arrangement is called the hierarchy of classification.
Kingdom → Phylum → Class → Order → Family → Genus → Species
Each organism is given a scientific name by binomial nomenclature. The name has two parts – genus and species. For example, mango is Mangifera indica and human is Homo sapiens. This method was given by Carl Linnaeus.
Modern man developed from primitive man slowly, over millions of years.
- Primitive man lived on trees and walked on four limbs.
- Slowly he began to walk on two legs. His hands became free.
- He used his hands to make stone tools.
- His brain became bigger. He learnt to use fire and hunt in groups.
- Modern man walks upright and has a large brain. He can speak, farm and build homes.
Each change helped him to survive better. This is adaptation.