Living Science 2020 2021 Solutions for Class 7 Science Chapter 19 Our Forests are provided here with simple step-by-step explanations. These solutions for Our Forests are extremely popular among Class 7 students for Science Our Forests Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Living Science 2020 2021 Book of Class 7 Science Chapter 19 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Living Science 2020 2021 Solutions. All Living Science 2020 2021 Solutions for class Class 7 Science are prepared by experts and are 100% accurate.
Page No 227:
Question 1:
The crowns of trees in a thick forest together form a 'roof' over other plants. What is this roof known as?
Answer:
The roof formed by the crown of trees present in a thick forest is called a canopy.
Page No 227:
Question 2:
The understorey in a thick forest has many layers. Describe three layers in the understorey.
Answer:
The understorey of a forest cover has following layers:
1. The first layer is formed by the smaller trees which grow beneath the canopy.
2. The second layer is formed by tall grasses and shrubs.
3. The third or lowest layer in an understorey is formed by herbs.
Page No 227:
Question 3:
Why do forests generally do not get flooded even after heavy rains?
Answer:
The heavy rains are progressively slowed down by the leaves of the plants and trees of the plants. This prevents the stagnation and collection of water on the forest floor, which decreases the chances of floods.
Page No 227:
Question 4:
Air in a forest is generally cooler and has more moisture than air in an open area. Why?
Answer:
The plants and trees present in a forest continually lose water by the process of transpiration. This water is added to the surrounding air and it increases the moisture content of the air and makes it much cooler as compared to an open area.
Page No 231:
Question 1:
Plants in the forest are useful to animals in many ways. Animals are also useful to plants. List three ways in which animals are useful to plants.
Answer:
Animals are useful to the plants in the following ways:
1. Animals such as bat, humming bird and butterfly help in the pollination of plants.
2. Many animals also help in the seed dispersal process.
3. The dead remains of animals and their excreta serves as a good source of nutrients for the growth of plants.
Page No 231:
Question 2:
Consumers (or heterotrophs) are those animals that eat plants. Do you agree? Give reasons.
Answer:
No, consumers do not only include those animals that consume plants. Consumers represent a large group of heterotrophic organisms that directly or indirectly depend on the plants. These include herbivores, carnivores and omnivores.
Page No 231:
Question 3:
Plants and animals take nutrients from the soil. Ultimately these nutrients must go back to the soil. Why? How does this happen?
Answer:
The nutrients are recycled back to the soil by the action of decomposers. These organisms decompose dead remains of animals as well as plants and breakdown them into different molecules. These molecules are returned back to the soil and are again used for the growth of new organisms.
Page No 231:
Question 4:
Food chains in nature are not independent from each other. They are interconnected because one organism may appear in several food chains. What do these interconnected food chains together form?
Answer:
The interconnected food chains constitute a food web. In a food web, numerous food chains are interlinked and this connection is important for maintaining the balance of nature.
Page No 231:
Question 5:
We have to cut trees as we need wood for various purposes. What advantage does planned harvesting of trees has over cutting all trees in an area?
Answer:
Planned harvesting provides following benefits as compared to cutting all trees in an area:
1. Wood can be obtained in a more efficient manner and soil erosion can be reduced by planned harvesting.
2. The forest cover can be maintained and forest resources can be conserved by planned harvesting.
Page No 232:
Question 1:
The lowest layer in the understorey is formed by
(a) shrubs
(b) herbs
(c) trees
(d) tail grasses
Answer:
(a) shrubs
The lowest layer in the understorey is formed by shrubs.
Page No 232:
Question 2:
Which of these is not obtained from a forest product?
(a) paper
(b) furniture
(c) plastics
(d) medicines
Answer:
(c) plastics
Plastic is not a forest product, while paper, furniture and medicines are forest products. They are obtained from the forests.
Page No 232:
Question 3:
Which of the following are called producers?
(a) herbivores
(b) carnivores
(c) green plants
(d) bacteria and fungi
Answer:
(c) green plants
Green plants are called producers because they can produce their own food by photosynthesis.
Page No 232:
Question 4:
The first link in all food chains are
(a) herbivores
(b) carnivores
(c) green plants
(d) none of these
Answer:
(c) green plants
Green plants serve as the first link in all food chains. They are also called producers.
Page No 233:
Question 5:
Which of these enable nutrients present in the bodies of plants and animals to go back to the soil after they die?
(a) producers
(b) primary consumers
(c) secondary consumers
(d) decomposers
Answer:
(d) decomposers
Decomposers enable nutrients present in the dead bodies of plants and animals to go back to the soil. Examples of decomposers include bacteria and fungi.
Page No 233:
Question 6:
The primary source of energy in nature is
(a) oxygen
(b) carbon dioxide
(c) fuels
(d) sun
Answer:
(d) sun
Sun is the primary source of energy for all living organisms.
Page No 233:
Question 7:
Which of the following does a forest prevent?
(a) floods
(b) soil erosion
(c) water table from going down
(d) all of these
Answer:
(d) all of these
Forests prevent soil erosion and floods. They also prevent water table from going down.
Page No 233:
Question 8:
Which of the following does a forest NOT do?
(a) supply oxygen
(b) supply carbon dioxide
(c) cool the air
(d) increase rainfall
Answer:
(b) supply carbon dioxide
A forest does not supply carbon dioxide. However, the trees in the forest release oxygen during the process of photosynthesis. Forests cause sufficient rainfall on earth and also keep the climate cool.
Page No 233:
Question 9:
Plants DO NOT depend on animals for
(a) pollination
(b) food
(c) seed dispersal
(d) nutrients
Answer:
(b) food
Plants do not depend on animals for food. They can produce their own food by photosynthesis. This is why they are also called producers.
Page No 233:
Question 10:
Flow of energy in nature takes the following path:
(a) carnivores → herbivores → green plants
(b) green plants → herbivores → carnivores
(c) sun → green plants → herbivores → carnivores
(d) sun → carnivores → herbivores → green plants
Answer:
(c) sun → green plants → herbivores → carnivores
Food chain is a simple representation of energy flow in nature. The correct order of energy flow in a food chain is:
sun → green plants → herbivores → carnivores
Page No 233:
Question 1:
What is the name given to the cover of branches of tall trees in a forest?
Answer:
Canopy is the name given to the cover of branches of tall trees in a forest.
Page No 233:
Question 2:
Name one medicinal plant.
Answer:
Neem is an example of medicinal plants. Its leaves are used as medicine.
Page No 233:
Question 3:
If there are no plants in the soil, heavy rain will cause extensive soil ________
Answer:
If there are no plants in the soil, heavy rain will cause extensive soil erosion.
Page No 233:
Question 4:
Forests are called 'green lungs' because they supply ____________ to the atmosphere.
Answer:
Forests are called 'green lungs' because they supply oxygen to the atmosphere.
Page No 233:
Question 5:
Forests help in cloud formation as they release __________ in the air.
Answer:
Forests help in cloud formation as they release water vapour in the air.
Page No 233:
Question 6:
Are carnivores primary consumers or secondary consumers?
Answer:
Carnivores are secondary consumers as they feed on herbivores (animals who eat plants).
Page No 233:
Question 7:
A food chain shows the flow of energy from one organism to another. Which did this energy come from in the first place?
Answer:
Order of energy flow in a food chain is:
sun → green plants → herbivores → carnivores
Energy at the first place in this chain comes from sun.
Page No 233:
Question 8:
Name one decomposer that is not a microorganism.
Answer:
Cockroach is a decomposer that is not a micro-organism. It feeds on dead and decaying plants and animals.
Page No 233:
Question 9:
A food ___________ is made up of several connected food chains.
Answer:
A food web is made up of several connected food chains.
Page No 233:
Question 1:
Why is it dark inside a forest?
Answer:
It is dark inside a forest because the canopy leaves intercept the sunlight available to the forest. As a result, less than 50% of total sunlight falling on the top of the forests manage to pass through the canopy and go down to the plants in the forest.
Page No 233:
Question 2:
In an area in which a forest was cut to make a city, it was found that the water table went down. What could be the reasons for this?
Answer:
Trees and plants of forests help in seepage of rainwater into the ground. In the absence of forest, little rainfall seeps into the ground. In such cases, more groundwater is drawn out for irrigation and other purposes than it gets replenished by rainfall. This depletes the water table.
Page No 233:
Question 3:
Name five products that we get from forests.
Answer:
Five products that we get from forests are timber, spices, oils, medicines and wood.
Page No 233:
Question 4:
Name two scavengers. How are they useful to the environment?
Answer:
Scavengers are animals, who eat dead bodies of plants and animals. Vultures and crows are two scavengers. They eat dead bodies of plants and animals. This helps in keeping the environment clean.
Page No 233:
Question 5:
Give an example to show the interconnection between food chains.
Answer:
Several food chains that exist in nature are interconnected. Green plants are eaten by several plant-eaters. These plant-eaters in turn are eaten by several animal-eaters. In this way, many food chains are linked together to form a web called food web.
Page No 234:
Question 6:
How are forest fires controlled?
Answer:
Forest fires can be controlled by following methods:
i. By spraying fire extinguishing solutions.
ii. Strong blowers can be used to change the direction of the wind.
Page No 234:
Question 7:
What is 'afforestation'?
Answer:
Afforestation is the process of renewing a forest by planting more trees. However, the process is slow because new saplings take several years to grow.
Page No 234:
Question 1:
Mention two ways in which plants are useful to animals and two ways in which animals are useful to plants.
Answer:
Plants are useful to animals in the following ways:
(i) Plants provide oxygen to animals. They also act as food for some animals.
(ii) They reduce the pollutants present in air; thus, protecting animals. They also provide shelter to some animals.
Animals are useful to plants in the following ways:
(i) Animals help plants in pollination and seed dispersal.
(ii) Animal excreta and dead animals add nutrients to the soil and provide minerals for plant growth.
Page No 234:
Question 2:
What is a food chain? Explain with an example.
Answer:
Food chain is a simple representation of energy flow in nature. It shows the relationship between producers, consumers and decomposers with the help of arrows showing who eats whom.
For example, a grasshopper feeds on leaves of a plant, a frog eats grasshopper and the frog in turn is eaten by a snake. The last link of a food chain is occupied by decomposers, who feeds on dead plants and animals.
Page No 234:
Question 3:
Explain the meaning of a 'food web'.
Answer:
An interconnected network of food chains that form a multitude of feeding connections among different organisms of a biotic community is called a food web.
A food web shows how different animals are interconnected by different paths.
Page No 234:
Question 4:
Explain how nature maintains a balance between living things.
Answer:
"To kill and to be killed, to grow and to die and get decomposed" is the law of nature. With the help of this law, nature maintains the population of each species of animals in sufficient numbers.
For example, consider a simple terrestrial food chain:
plants → grasshopper → frogs → snake → eagle
Suppose, there are no eagles in a community. In the absence of eagles, the population of snake will increase. Increased population of snake will eat more frogs. Gradually, the population of frog will decrease.
Decrease in the population of frog will lead to increase in the population of grasshopper. Now, grasshopper will eat more plants. Decrease in the population of plants would disturb the entire ecological balance.
Page No 234:
Question 5:
When you conserve forests, you also conserve soil. Discuss.
Answer:
Forests prevent soil erosion and floods. Hence, they conserve soil. In the absence of forest, soil erosion occurs more rapidly, exposing the lower hard and rocky layer. As a result, the soil loses humus and becomes less fertile. Thus, fertile lands, which act as a source of living for farmers, get converted to a desert. This process is known as desertification of land.
Page No 234:
Question 6:
What do you mean by planned harvesting of forests? How does it help in conservation?
Answer:
Planned harvesting of forest is a method employed by the government to conserve forests. Under this, all the trees of a forest are prevented from getting cut while converting it into an agricultural land. Cutting of all the trees may lead to soil erosion and other natural problems.
Planned harvesting of forests maintains a balance between deforestation and afforestation, i.e., regeneration of new plants. Thus, it helps in conservation of forest.
Page No 234:
Question 7:
In what way are wildlife conservation, forest conservation and soil conservation related?
Answer:
Wildlife conservation, forest conservation and soil conservation -- all three are inter-related. It is because, by conserving the forest, wildlife and soil are automatically conserved.
When we conserve forests, we conserve soil by preventing soil erosion. They also maintain the fertility of soil.
Similarly, trees in the forest provide shelter and safety to animals. They also provide food to wildlife. Thus, conservation of forest means conservation of wildlife.
Page No 234:
Question 8:
List five ways in which forests are useful to us.
Answer:
Forests are useful to us in following ways:
(i) Forests prevent soil erosion and floods.
(ii) They maintain the balance between carbon dioxide and oxygen levels in the atmosphere.
(iii) They reduce global warming by using carbon dioxide during photosynthesis.
(iv) They maintain the climate of a place and cool the environment by releasing water vapours in the air.
(v) They provide all basic needs of the mankind including food, clothing, and shelter.
Page No 234:
Question 9:
Can large scale cutting down of forests have an effect on rainfall in the area? Give reasons.
Answer:
Yes, large scale cutting down of forests can affect the rainfall in the area. Trees absorb water through their roots and release water vapours in the air through transpiration. These water vapours then condense to form clouds. When water droplets (in form of clouds) become big, they fall as rain. When rain falls on the ground, the roots of the trees help water to seep down in the ground. Thus, by cutting down the forests, the entire process of water cycle would get affected, which in turn would result in the reduction of rainfall.
Page No 234:
Question 1:
What do you think will be the consequences if all forests on the earth disappear?
Answer:
If all the forests on earth disappear, it will lead to the following consequences:
(i) There will be an increase in earth's temperature.
(ii) Animals will not get food and shelter.
(iii) Soil will not hold water, which will cause floods.
(iv) There will be no purification of air.
(v) There will be no recycling of nutrients.
Page No 234:
Question 2:
To conserve forests, we should ban cutting down of trees completely. Do you agree?
Answer:
No; though forest trees are cut for various desirable uses, it is not necessary to ban the cutting down of trees completely. However, it should be done at a slow rate to allow the forest trees regenerate naturally. Also, more trees should be planted to maintain a balance of trees.
Page No 234:
Question 3:
'A forest has no waste.' Why?
Answer:
A forest has no waste because dead bodies are consumed and the remains are recycled. When animals die in a forest, they are eaten up by scavengers such as crows and vultures. Scavengers feed on the dead bodies of animals which in turn keep the forest clean. Moreover, decomposers like bacteria and fungi also decompose dead organisms and wastes into humus, which contains nutrients for plants.
Page No 234:
Question 4:
Suppose in a forest, the number of carnivores became more than the number of herbivores.
What will be the consequence?
Answer:
If the number of carnivores in a forest becomes more than the number of herbivores, the population of herbivores will decrease, as carnivores feed on herbivores. Decrease in the population of herbivores will further lead to an increase in the population of green plants (producers), as herbivores feeds on green plants. Hence, 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 234:
Question 1:
Look at the graph. It shows a typical variation of populations of predators (wolves, tigers etc.) and prey (deer, rabbits etc.) in a habitat such as a forest.
Answer these questions.
1. Why is the predator population always lower than the prey population?
2. Point A is the rainy season. Why is the prey population increasing?
3. Why does the predator population starts increasing after the increase in the prey population?
4. As the predator population increases, why does the prey population starts declining (point B)?
5. Why does the predator population now start to decrease (point C)?
6. Will the graph maintain the same shape if a calamity such as disease struck the prey and they died in large numbers? What do you expect will happen?
Answer:
1. Lower predator population than the prey ensures that prey population does not reach to extent of extinction. If predator population exceeds the prey population, it could lead to their extinction.
2. After the rainy season, the availability of food increases for the prey and conditions become favourable for them.
3. Increase in prey population means increased availability of food for predators. The predators population also increase but only to a certain extent.
4. If the predator population is going to increase, so will their demand for food. More number of prey will be feeded on which would result in a decline in their population.
5. At point C, we can see that the population of prey is also decreasing. If the population of prey decreases, the availability of food for predators also decreases.
6. No, the graph will not remain the same if a calamity strucks and kills most of the prey. If prey will die in large number, there will be a scarcity of food for the predators and eventually they would also die.
Page No 235:
Question 1:
Nagina uses recycled paper as much as possible. In what way does she help the environment?
Answer:
Paper is one of the most common product of trees that we use in our daily lives. The amount of paper wasted directly equals to the number of trees that have to be cut down to compensate the wastage of paper. Recycling of paper, helps in the protection of one of our major resources i.e. our trees.
By recycling paper not only we save our trees but also reduce the load on waste management.
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