Solved examples for class 7 science : Chapter 2
Forests: Our Lifeline
I. Multiple Choice Questions (MCQs).
Q.1. All the plants and animals constitute the ______________ of forests.
a) abiotic components
b) biotic components
c) non-living components
d) none of these
Answer: (b) biotic components
Q.2. The main product of forests is
Answer: (a) timber
Q.3. The latex is used for making
d) all of these
Answer: (c) rubber
Q.4. The trees in the forest has different types and sizes of
Answer: (a) crowns
Q.5. Which of the following is not a reason of decline in forests?
f) Developmental projects
Answer: (d) Afforestation
II. Fill in the blanks by selecting appropriate words from the given list :
List : climate, coconut, excreta, water, habitat
Q.1. A _________________ is made up of two types of components—biotic and abiotic.
Q.2. Trees help to regulate the ______________.
Q.3. Forest forms an important part of the ______________ cycle.
Q.4. Coir is obtained from ______________ and is used to make rope, doormat and mattresses.
Q.5. Animal ______________ also provides nutrients to the soil.
III. Match the items of Column A with those of Column B.
Answer: 1-e,2-a, 3-d 4-b, 5-c
IV. Write ‘T’ for the true and ‘F’ for the false statements.
Q.1. Approximately one-third of earth’s land surface is covered with forests.
Q.2. There are many plants that are used to make medicines.
Q.3. Chipko Movement was started in 1990.
Q.4. The increasing population has severely depleted the forest.
Q.5. The microorganisms, which help in maintaining the supply of nutrients to the plants, are known as scavengers.
Answer: 1- T, 2-T, 3-F, 4-T, 5-F
V. Very Short Answer Questions.
Q.1. Write the names of two biotic components of a habitat.
Answer: Plants and Animals
Q.2. Name the gas whose high concentration in the atmosphere is responsible for global warming.
Answer. Carbon dioxide
Q.3. Write the name of a plant which is used to make medicines.
Q.4. Define decomposers.
Answer. The microorganisms, which help in maintaining the supply of nutrients to the plants, are known as decomposers.
Q.5. Define agroforestry.
Answer. Agroforestry is a natural farm management system that along with agriculture and the integration of trees on farms has many environmental benefits.
VI. Short Answer Questions.
Q.1. How can you say that forests are an important part of the water cycle?
Answer. Due to the thick vegetation, leaves add a lot of water to the atmosphere by the way of transpiration that Later undergoes condensation and comes down as rain. Thus we can say that the forest forms an important part of the water cycle.
Q.2. What will happen if a food chain is disturbed? Explain with the help of an example.
Answer. If food chain is disturbed, the balance of plant and animal populations within a community will disturbed. For example, when there are too many deer, there will be insufficient shrubs for all of them to eat. Many deer will starve and die. Fewer deer will lead to shortage of food for the lions and foxes to eat and some of them will starve to death.
Q.3. What do we get from forests? Explain briefly.
Answer. Following things we get from forest:
• Trees that grows in forest provide us many edible substances such as fruits, nuts and spices.
• There are many plants that are used to make medicines. Acacia, neem, amla, eucalyptus, etc., are used in making many ayurvedic medicines. The cinchona provides quinine, the medicine for treating malaria.
• Plants growing in forests provide fibre used to make paper, cloth, rope, etc. Some examples are jute, Linen, hemp, cotton and flax.
• Coir is obtained from coconut which is used to make rope, doormat and mattresses.
Q.4. How do forests provide home to large number of animals? Explain briefly.
Answer. Forest provides shelter to large number of animals. Some animals depend on plant for shelter and safety. Trees provide protection from rain and shade from heat of the Sun to the animals. Most of the birds make their nest on branches and trees. Monkeys, apes and bats also live on trees.
Q.5. List any four reasons of decline in forests.
Answer. Reasons of decline in forests
i. Increasing population
ii. Construction of dams, roads, railways, etc.
iv. Demand of timber
VII. Long Answer Questions.
Q.1. What do you mean by food chain and food web? Describe them with well labelled diagram.
Answer. The transfer of energy from green plants [the primary producers) to decomposers, through a sequence of organisms in which each eats the one below it in the chain and is eaten by the one above, known as food chain.
A number of food chain exists together in a forest forming a food web. The organisms in the food web are all interdependent. The arrow indicates the direction of energy flow.
This interdependent of the population within a food chain helps to maintain the balance of plant and animal populations within a community. The herbivorous animals depend upon plants for food. The carnivorous feed on the herbivorous and so on.
Q.2. Write a short note on interactions among plants and animals in a forest.
Answer. A large number of plants and animals inhabit forests. These organisms depend upon each other to survive. All animals are dependent on plants directly or indirectly for food, oxygen and many other things. Plants are also dependent on animals. Plants supply oxygen to the atmosphere which is essential for our life and also maintain the balance of oxygen and carbon dioxide. Hence, forests are also called green lungs. Food items are also obtained from plants. Plants also provide shelter to monkey, apes, bat and moth to pollinate flowers and for dispersal of seed. Some microorganisms convert the dead plants and animals to humus. The transfer of energy from green plants (the primary producers) to decomposers, through a sequence of organisms in which each eats the one below it in the chain and is eaten by the one above, known as food chain.
Q.3. (a) What measures should be taken to protect the forest? Explain them briefly.
(b) What do you mean by agroforestry and social forestry?
Answer .a) Following measures can be taken to protect the forest:
(i) Afforestation programmes should be undertaken on a Large scale. When trees are cut to fulfil the requirements of people, more trees should be planted to avoid depletion of this natural resource.
(ii) Special pastures [grazing fields] should be made to avoid overgrazing by cattle.
(iii) Government should make stringent Laws to protect forests so that these are not further converted into barren Lands.
(iv) People Living in the rural and forest areas should be encouraged to cut branches and twigs of the trees for their daily requirements.
(v) Horticulture should be encouraged as an alternative source of income.
b) Agroforestry is a natural farm management system that along with agriculture and the integration of trees on farms has many environmental benefits.
Social forestry involves making use of all unused and fallow Land and planting trees in and around agricultural fields, along railway Lines, roadsides, river and canal banks.