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Page No 241:

Question 1:

Which of the following is a decomposer?
A. crow
B. sparrow
C. fungi
D. bacteria

(a) A and B
(b) Only A
(c) C and D
(d) A, C and D

Answer:

(c) C and D

Bacteria and fungi are examples of decomposers. Decomposers are organisms that break down dead organisms and wastes into organic matter.

Page No 241:

Question 2:

Shellac is obtained from
(a) pine tree.
(b) an insect
(c) an elephant.
(d) a herb.

Answer:

(b) an insect

Shellac or lac is a resin that is obtained from lac insect. It is used for making varnish.

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Question 3:

A food web consists of
(a) producers only
(b) consumers only.
(c) interconnected food chains.
(d) unconnected food chains.

Answer:

(c) interconnected food chains

A food web is an interconnected network of food chains in a given area.

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Question 4:

Scavengers eat:
(a) dead and decaying plants and animals.
(b) dead animals.
(c) only dead plants.
(d) all the above.

Answer:

(b) dead animals
Scavengers feed on dead bodies of animals. Examples include crows, jackals and vultures. 

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Question 5:

A species that no longer exists is said to be
(a) protected.
(b) endangered
(c) found somewhere else.
(d) extinct.

Answer:

(d) extinct
Species that no longer exist on earth are called extinct. Dodo and dinosaur are examples of extinct species.

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Question 6:

Biotic factors include
(a) plants and animals only.
(b) plants, animals and decomposers only.
(c) all living organisms.
(d) plants, animals and scavengers only.

Answer:

(c) all living organisms
Biotic factors include all living organisms -- animals, plants and microorganisms.

Page No 241:

Question 7:

Which of the following groups consist of only forest products?
(a) nylon, rope, medicine, potato chips, bamboo flute
(b) eucalyptus oil, bamboo flute, paper napkins, rubber
(c) eggs, sunflower oil, toothbrush, cornflakes
(d) aluminium foil, silk, sari, matchbox, honey

Answer:

(b) Eucalyptus oil, bamboo flute, paper napkins, rubber

Eucalyptus oil, bamboo flute, paper napkins and rubber are forest products. They are obtained from forests.

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Question 8:

Study the food web shown here. Which list contains all the consumers in this food web?
figure

(a) grasses, shrubs
(b) grasses, shrubs, grasshoppers, mice, rabbits
(c) hawks, foxes
(d) grasshoppers, mice, rabbits, birds, hawks, foxes.

Answer:

(d) grasshoppers, mice, rabbits, birds, hawks, foxes

Consumers are organisms that obtain their food by eating or digesting other organisms. They include herbivores and carnivores of the ecosystem. In the given food web, grasshoppers, mice, rabbit, birds, hawks and foxes are consumers. Grasses and shrubs are producers.

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Question 9:

Microorganisms in a forest act upon dead plants to produce
(a) sand.
(b) mushrooms.
(c) humus.
(d) wood.

Answer:

(c) humus
Microorganisms like bacteria and fungi act upon dead bodies of plants and animals to produce humus, which is rich in organic matter.



Page No 242:

Question 10:

Mark the following statements true or false. Rewrite the false statements correctly.
(a) Forests help in soil and water conservation.
(b) Afforestation destroys forests.
(c) Plaints, the producers in the food chain, are heterotrophs.
(d) the ultimate source of energy for all living things are green plants.
(e) Killing plants and animals indiscriminately destroys the balance in nature.
(f) Scavengers cause decomposition of dead animals.
(g) Sheep are omnivores because they eat grass and they in turn are eaten by man.
(h) All living and non-living things in a particular area and their relationship with each other forms the ecosystem.

Answer:

(a) True.

(b) False.
Deforestation destroys forests. Afforestation maintains forest.

(c) False.
Plants, the producers in the food chain, are autotrophs.

(d) False.
The ultimate source of energy for all living things is sun.

(e) True.

(f) False.
Decomposers cause decomposition of dead animals into humus, which contain nutrients for plants.

(g) False.
Sheep are herbivores because they eat grass and they in turn are eaten by men.

(h) True.

Page No 242:

Question 11:

Why is the starting point of a food chain always a plant?

Answer:

A food chain always starts with a plant (producer), which is an organism that makes food. Green plants absorb energy of the sun to manufacture their food by photosynthesis. This stored energy (in the form of food) is then passed on from producer (plants) to plant-eaters and to animal-eaters.

Page No 242:

Question 12:

How are bacteria and fungi important in the forest ecosystem?

Answer:

Bacteria and fungi are examples of decomposers. They play an important role in forest ecosystem.

  1. They help in maintaining the supply of nutrients to the growing plants in the forest. This is done by decomposing the dead bodies of dead plants and animals into mineral salts which go into the soil as nutrients for plants.
  2. They also prevent dead plants and animals and their wastes from piling up in the forest. They carry out the process of decomposition. Decomposition involves breaking down of organic matter from dead bodies of plants and animals into mineral salts (in the form of humus), water and carbon dioxide, which go into the soil and air, respectively.

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Question 13:

Name ten products we get from forests.

Answer:

Rosewood, perfume, paper, gum, rubber, turpentine oil, aloe vera, honey, turmeric, shellac are the products that we get from forests.

Page No 242:

Question 14:

(a) How do animals help plants?
(b) How do plants help animals?
List at least four ways in each case.

Answer:


(a) Animals help plants in following ways:

  1. They help plants in pollination and seed dispersal.
  2. Animal excreta and dead animals add nutrients to the soil and provide minerals for plant growth.
  3. Cow dung serves as a source of manure for plants.
  4. Bacteria and fungi act as decomposers and help in decomposition of dead plants.

(b) Plants help animals in following ways:

  1. They provide oxygen to animals.
  2. They act as food for some animals.
  3. They maintain the climate of a place.
  4. They provide shelter to many animals.

Page No 242:

Question 15:

How does deforestation affect the environment?

Answer:

Deforestation increases the temperature and pollution level on earth. Plants absorb carbon dioxide from the atmosphere to perform photosynthesis. If plants are destroyed, the level of carbon dioxide in the atmosphere will increase. As a result, carbon dioxide will trap more radiation, thereby adding to global warming. Global warming refers to an average increase in earth’s temperature. An increase in earth’s temperature will disturb the entire natural water cycle. As a result, there will be a change in the rainfall pattern, which in turn could lead to drought or flood.

Page No 242:

Question 16:

Explain with the help of an example how man's activity destroys the balance in nature.

Answer:

The relationship among living organisms in an ecosystem maintains the balance of nature. Human kills many animals without realising their importance in the ecosystem. These animals form a part of food chains and food webs. Man hunts and kills animals to earn money by selling their body parts. Eventually, the population of these animal decreases, thereby disturbing the food chains and food webs of which they form a part.
For example, if snakes are killed, the grasshopper population will increase in nature to such an extent that they will damage the entire plant species. It means if the population of any of the members in a food chain increases or decreases, it will affect the population of other members. This would disturb the balance in nature.

Page No 242:

Question 17:

How are forests useful to mankind? Explain briefly.

Answer:

Forests are useful to mankind in various ways:

  1. They provide all basic needs of mankind such as food, clothing and shelter.
  2. They provide us timber, which is widely used for making furniture, construction and other domestic purposes.
  3. They prevent soil erosion and floods. Roots of trees help to control soil erosion as roots bind the soil. This in turn prevents the topsoil from getting eroded by wind and water.
  4. Forests maintain a healthy balance between carbon dioxide and oxygen in the atmosphere. They provide us oxygen.
  5. Forests reduce global warming by using carbon dioxide (during photosynthesis). Carbon dioxide is the main greenhouse gas.
  6. Forest maintains the climate of a place. It cools the air by releasing water vapours into the air. This phenomenon is called vaporisation.
  7. Forests are filled with medicinal plants. Plants such as amla, Eucalyptus, neem, etc. are used for making several ayurvedic medicines. 

Page No 242:

Question 18:

Arrange the following organisms in a food chain.
(a) frog, fly, sugar, snake
(b) big, fish, shark, small fish, sea plant

Answer:

(a) Sugar → Fly → Frog → Snake

(b) Sea plant → Small fish → Big fish → Shark

Page No 242:

Question 19:

Due to indiscriminate cutting of trees by the villagers of Prahladpur, the forest in the outskirts of the village has very few trees left. List any two problems that these villagers might be facing now.

Answer:

Indiscriminate cutting of trees may lead to following problems to the villagers:

  1. Large scale cutting down of forests affects the rainfall in the area. Due to indiscriminate cutting down of forests, the entire process of water cycle would get affected, which in turn would result in the reduction of rainfall. Hence, the villagers will find difficulty in agriculture.
  2. Forest provides shelter and food to animals. When forests are destroyed, it would force the animals to go to other places in search of food and shelter. Sometimes, wild animals enter villages and start attacking cattle and human beings.

Page No 242:

Question 20:

Study the food web.
figure

(a) Name the producers in this food web.
(b) Name two consumers.
(c) List any two food chains that make up this web.
(d) The bird population in this region decreases due to an epidemic. What do you think will happen?

Answer:

(a) Grass and carrot are producers. They prepare their own food by photosynthesis.

(b) Snail and bird are two consumers. Consumers are organisms that obtain their food by eating or digesting other organisms. It includes herbivores and carnivores of the ecosystem.

(c) Grass →Rabbit → Fox

    Carrot → Snail → Frog → Bird → Cat

(d) The population of bird decreases due to an epidemic. As a result, the population of frog and snail, which birds controlled, increased.
     When the population of frog increases, the population of snail decreases. When the number of snail decreases, the grass and carrot on which they feed increase.
      When the population of snail increases, the grass and carrot on which they feed decrease. When the grass and carrot decrease, the snail population decreases again as they do not get enough food. Hence, decrease in the population of plants would disturb the entire ecological balance.
        
This means, if the population of any of the members in a food chain increases or decreases, it will affect the population of other members. Their number will either increase or decrease substantially.

Page No 242:

Question 21:

Find the odd one out in each of the following groups giving reasons.
(a) sun, water, fossil fuels, animals
(b) deer, cow, human, goat, elephant
(c) forest, sun, water, minerals
(d) gum, perfume, tin container, apple

Answer:

(a) Animals
Animals are biotic factors, i.e., living components of the environment, whereas sun, water and fossil fuels are abiotic factors (non-living components).

(b) Human
Humans are omnivores, whereas deer, cow, goat and elephant are herbivores.

(c) Forest
Plants prepare their food by using energy from sun, water and carbon dioxide from the atmosphere and minerals (nutrients).

(d) Tin container
Tin container is a non-forest product, whereas gum, perfume and apple are forest products.



Page No 243:

Question 22:

The food chains are jumbled in the following lists. Arrange them in the correct order.
(a) rat, grains, eagle, snake
(b) small fish, big fish, small water plants, small water animals, bear

Answer:

(a) Grains → Rat → Snake → Eagle

(b) Small water plants → Small water animals → Small fish → Big fish → Bear

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Question 23:

Mark the statements as true or false. Correct the false statements.
(a) Bacteria are scavengers of nature.
(b) A species that no longer exists can be considered as extinct.
(c) Food chains always start with small animals.
(d) Cutting down of trees is called afforestation.
(e) All plants and animals are dependent on each other.
(f) Nature maintains a balance if ecosystems are left undisturbed.
(g) A duck eats snails and algae therefore it can be considered as a carnivore.
(h) Herbivores are always second on the food chain.

Answer:

(a) False.
Bacteria are decomposers of nature.

(b) True.

(c) False.
Food chains always start with producer (green plants).

(d) False.
Cutting down of trees is called deforestation.

(e) True.

(f) True.

(g) False.
A duck eats snails and algae; therefore, it can be considered as an omnivore.

(h) True.



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