Science textbook solution for Class 7 science Chapter 1- The Living World : Adaptations and Classification


Important points to remember :
  1. Gradual changes occur in the body parts and also in the behaviour of organisms which help them to adjust to their surroundings. Such changes are called adaptations. 
  2. They take place over a long period of time. Spring-like tendrils on the stems of some climbers is an example of adaptation.
  3. Adaptation is not a sudden process. It is gradual and continuous. Differences in the structure and appearance of present-day animals and animals of thousands of years ago are the adaptations that occured according to prevailing conditions. 
  4. It is our duty to conserve this diversity. Charles Darwin, a biologist, studied numerous types of plants and animals and suggested that only those organisms are likely to survive which can best adapt themselves to a changing environment. This is called the theory of survival of the fittest. This is Darwin’s first principle.
  5. If an organism is born with a new beneficial characteristic and is able to survive, this change is preserved in the next generation. This is Darwin’s second principle and is called the theory of ‘natural selection’.


Question 1: Find my match!

Group A           Group B 
1) Lotus.          a) Flower and leaves                                            attract insects

2) Aloe.            b) Haustorial roots for.                                        absorption of food

3) Cuscuta.     c) Adapted to live in deserts

4)Venus flytrap.     d) Adapted to live in water

Answer : 
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


Question 2: Read the paragraph and answer the following questions.
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?
Answer : Melanin is responsible for determining skin and hair color. The more of it one has the darker his skin. Exposure to sunlight also accounts for the amount of melanin in the body. The thick skin protects internal organs from injury and the fat provides an insulation against loss of heat from the body.

b) Why do we live in flocks sticking close to each other?
Answer: Penguins live in flocks sticking close to each other inorder to keep themself warm . Penguins are mammals which live in extremely cold places so, to keep their body warm and to safe themself from prey they stick to each other.

c) Which geographical region do I inhabit? Why?
Answer : Penguins are a type of aquatic, flightless bird. They live exclusively in Southern hemisphere but not all the Penguins live in extremely cold climatic conditions of Antarctica.

d) Which adaptations should you have to enable you to live permanently in the polar region? Why?
Answer : adaptation that should we have to enable to live permanently in polar region is , we must have fur so that we can live in the too cold region. than our feet should be trapping type so that we may not slip in the ice. our hearing power must be high so that if any animal is coming , we can know.


Question 3: Who is lying?
a) Cockroach – I have five legs.
Answer : The cockroach is lying beacuse it has six legs and not five.

b) Hen – My toes are webbed.
Answer : True

c) Cactus – My fleshy, green part is a leaf.
Answer : The cactus is also lying because its fleshy, green part is a stem and not a leaf.


Question 4: Read each of the following statements. Write a paragraph about adaptation with reference to each statement.

a) There is extreme heat in deserts.
Answer : There is extreme heat in the deserts because they are located close to sun and there is hardly any water found.

b) Grasslands are lush green.
Answer : Grasslands are lush green because of the rainfall which causes proper photosynthesis giving them a bright green colour and is dominated mostly by the same kind of species which can feed vast number of animals. Grasses are tall so that animals like tiger, lion, elephant can remain hidden in them.

c) Insects are found in large numbers.
Answer : Insects are found in large numbers because they live and communicate in colonies with the help of sound,phremones, or the path .

d) We hide.
Answer : There are certain species which are able to hide themselves by blending their colour with that of the surrounding. This adaptive mechanism is termed as camouflage and is a method to protect oneself from the predators and prey. For example, grasshopper, lizards, butterflies, chameleon, frogs etc.

e) We have long ears.
Answer : One of the important functions of big ears in animals is to act as a cooling system. This adaptation is commonly found in animals that live in warmer climates. The large ears have thin skin and contain an extensive network of blood vessels that provide a large surface area for heat exchange.


Question 5: Answer the following.
a) Why is the camel called the 'Ship of the desert'?
Answer : Camel is called the "Ship of Desert" because it is the only mean of transportation found in deserts which helps human being go from one place to another easily in the desert.
  1. Camels have large, flat feet that are covered by thick, protective pads. These pads, which form the bottom of their feet, are tough and leathery, and help prevent camels’ feet from being burned by desert sands as they walk, and keep them from sinking into the sand, which in turn saves valuable energy. 
  2. They have natural eye protection in the form of a double row of eyelashes and three eyelids, which help keep sand and dust out of their eyes and shield them from the sun's rays. 
  3. Camels can go as much as a week (in hot weather), and sometimes months (in colder temperatures) without water, and it was once even erroneously thought that they could store water in their humps.

b) How can the plants like cactus and acacia live in deserts with scarce water?
Answer : Plants like cactus and acacia are able to survive in desert places because of the special features they contain. They have got needle like leaves which reduces the rate of transpiration rate hence plants are able to store the little water for a long period of time. They have got thick stems for storage of water. Plants like cactus survive in the desert with scarce water because of the following reasons:
  1. They have leaves shaped in the form of thorns.
  2. Water is stored there and the plants also get moisture from the ground.
  3. They always have moisture (water) in them. and that is why they survive in hot places like deserts with scarce water.

c) What is the inter-relationship between adaptations of organisms and their surroundings?
Answer : The inter relationship between adaptation of organism and their surrounding is meant very crucial, that the organism has to be in the environment by satisfying the needs of their shelter, climate food and to maintain their various biological activities. The animal like polar bear can be found only in cold region, not in hot region because it cannot survive the temperature and animal like black bear cannot be in cold region and cannot handle the environment.
Hence, the adaptation to the environment is very crucial for survival.

d) How are organisms classified?
Answer :  All living organisms are classified into groups based on very basic, shared characteristics. Organisms within each group are then further divided into smaller groups. These smaller groups are based on more detailed similarities within each larger group. This grouping system makes it easier for scientists to study certain groups of organisms. Characteristics such as appearance, reproduction, mobility, and functionality are just a few ways in which living organisms are grouped together. These specialized groups are collectively called the classification of living things. The classification of living things includes 7 levels: kingdom, phylum, classes, order, families, genus, and species .


# Use your brain power
1. Why does water trickle off lotus leaves?
Answer : Lotus plants have super hydrophobic surfaces. Water drops that fall onto them bead up and roll off. These leaves not only stay dry, but the droplets pick up small particles of dirt as they roll, so that the lotus leaves are even self-cleaning

2. Why don’t the leaves of these plants rot in water ?
Answer : The leaves of lotus do not rot in water because they have a waxy coating on it which which prevents from rottening and decaying. As the stem of the lotus has a layer of waxy coating. lotus leaf is both adapted for water and has its cellular functions to keep it from decomposing.

3. Why are their roots short and fibrous?
Answer : The plants that are not deep rooted and are lower to the ground have fibrous root system.

It is the fibrous roots that enable the plants to be quick in responding to fertilizers and be better at adapting themselves to drought conditions.

The fibrous root system helps the plants to absorb surface water quickly. Monocot plants usually have fibrous roots.

4. What is the main difference between vehicles on the road and aeroplanes?
Answer : The biggest difference between airplanes and cars is that the car has a smaller fuel tank so you will spend less on gas than an airplane. In a car, you don't look in the engine unless something is wrong. With a plane, you check the engine every time for avoiding issues and other dangerous items.

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