Saturday , September 26 2020
7th Class CBSE Science NCERT Book

Forests: Our Lifeline – 7th NCERT CBSE Science Ch 17

Forests: Our Lifeline 7th Class NCERT CBSE Science Chapter 17

Question: List some animals which live in deeper areas of the forest.

Answer: Boars, bison, jackals, porcupines, elephants, etc., live in the deeper areas of the forest.

Question: Paheli while moving in a forest observed that there was no noise pollution, though lots of heavy vehicles were passing from the nearby highway. Explain why.

Answer: Paheli observed that there is no noise pollution in a forest even though there are lots of heavy vehicles passing from the nearby highway. It is because trees present in the forest absorb the noise.

Forests: Our Lifeline NCERT – Question: Give the reason behind variations found in the forests of different regions.

Answer: The variation in the type of plants and animals is found in different forests because of the climatic conditions of that particular area.

Question: Paheli wrote a food chain in the following way:

Frog → Eagle → Insects → Grass → Snake

The chain is not in the correct order. Help her to write the food chain correctly.

Answer: The correct food chain is

Grass → Insects → Frog → Snake → Eagle

Question: Are there similar kind of trees in every forests?

Answer: No, due to different climatic conditions, there are variations in the types of trees and other plants. From forest to forest.

Question: State the consequence when one food chain is disturbed in an ecosystem.

Answer: Since, all food chains are interlinked disturbance in one food chain will affect the other food chain in a forest.

Forests: Our Lifeline NCERT – Question: What is a canopy?

Answer: The uppermost branches and leaves of tall trees act like a roof over forest ground, this is called a canopy.

Question: While going inside a forest, it becomes darker. Why?

Answer: In a forest, big trees, shrubs and other plants are found. They trap solar radiation for photosynthesis.
So, the sunlight does not reach at the forest floor, thus making it dark.

Question: A bunch of seedlings were seen sprouting on a heap of animal dropping in a forest. How do you think is the seedling benefited from the animal dung?

Answer: The seedling was being benefited from the animal dung as the decaying animal dung provided nutrients to the growing seedlings.

Forests: Our Lifeline NCERT – Question: Consider the following organisms: Grass, birds, frog, crow, tiger, vulture, toadstool, deer.

Which of these

  1. can eat the dead animals
  2. can form a three step food chain?

Answer:

  1. Crow, vulture
  2. Grass → Deer → Tiger

Question: Give names of any four birds which you expect to see in a forest.

Answer: The four birds which we expect to see in a forest are jungle crow, hornbill, myna and koel.

Question: Draw any simple food chain in a pond.

Answer: A typical food chain in a pond is

Algae → Small fishes → Large fishes

Question: Name any four useful products other than wood, which we get from forests.

Answer: Four useful products other than wood which we get from forests are gum, spices, fodder for animals and medicinal plants.

Question: Deforestation may lead to floods. Why?

Answer: Deforestation leads to floods as lesser number of trees will be available due to deforestation. In the absence of trees, the soil will not hold water leading to floods.

Question: All the needs of animals living in a forest are fulfilled. Justify this statement in a few sentences.

Answer: Forest provides home (shelter), food and water to the animals living there. Thus, all the needs of animals living in a forest are fulfilled.

Forests: Our Lifeline NCERT – Question: Forests are valuable resources. Explain.

Answer: Forest products play vital role in socio-economic development. We get food (cereals, pulses, fruits), fire wood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance. It is also the home of diverse wildlife which maintains the ecosystem. Thus, forests are valuable resources.

Question: Plants help in maintaining O2– CO2 cycle. Explain it in the light of photosynthesis and respiration.

Answer: Photosynthesis is the process during which CO2 is used by the plants and O2 is released as a products. This O2 is used by the animals for their respiration and CO2 is released during it which is again used for photosynthesis by plants. In this way, O2– CO2 cycle is balanced by plants.

Question: Forests are called green lungs. Why?

Answer: The forests provide us oxygen to breathe. If we rapidly cutting down forests means we are cutting down the oxygen supply to us. That is why they are called green lungs.

Question: Two friends shared their experiences of their vacation trip to two different forests. Do you think they would have seen the same type of plants and animals during their respective trips? Give reason.

Answer: No, they would not have seen the same type of plants and animals. This is so because climatic conditions in the two forests would vary leading to variations in the types of plants and animals.

Forests: Our Lifeline NCERT – Question: Write differences between decomposers and scavengers.

Answer: Difference between decomposers and scavengers is

Decomposer Scavenger
These are the microbes which break dead organic matter into simple molecules to be used by plants again. These animals eat the body of dead animals and are called cleaning agent of forests, e.g. jackal, fox, vultures, etc.

Question: Plants are known as the producers of a food chain. Give reason.

Answer: Plants are known as the producers of a food chain. It is because green plants (autotrophs) make their own food from carbon dioxide and water in the presence of sunlight and chlorophyll by a process called photosynthesis and provide food to all living organisms which live in the forest.

Question: Life would be impossible without plants. Explain, how.

Answer: All green plants are producers. They make food by the process of photosynthesis using water C02 and sunlight. All forms of animals depend on plants for food. So, if there no plants, no food will be there. Plants are give oxygen also during photosynthesis, and there would be no oxygen in absence of plant. These two basic needs make plants important for us and we cannot think of life without plants.

Question: Y and Z are two types of organism which are found in the forests. Y eats up dead animals while Z breakdown the body of the dead animals into simpler substances.

  1. What is the general name of organism Y?
  2. Write one example of Y type organism.
  3. What is general name of organism Z?
  4. Write one example of Z type organism.

Answer:

  1. Scavenger
  2. Vulture
  3. Decomposers
  4. Fungi (mushroom)

Question: What happens when an animal dies in the forest?

Answer: The body of the dead animal is eaten up by scavengers like vultures, jackals, hyenas etc. These animals do the functions of cleaning in the forest. This also shows that nothing goes waste in the forests.

Question: Give any four factors which are responsible for the destruction of forests.

Answer: The four factors which are responsible for the destruction of forests are

  1. Construction of roads.
  2. Construction of buildings.
  3. Industrial development.
  4. Increasing demand of wood.

Question: Is it possible to construct a food chain without a producer? State the reason to support your answer.

Answer: No, in any food chain, producers are always at the beginning. It is the producer which provides food to all living organisms. In a food chain, if producer is absent, then there will be no flow of energy. So, we can say that it is not possible to construct a food chain without a producer.

Question: How can a pipal sapling would have grown on a side wall of some old buildings?

Answer: Animals disperse the seeds of certain plants with the help of their droppings. Therefore, pipal seed would have come to the wall by a bird dropping . On coming in contact with water and suitable nutrient medium, it would have grown into pipal sapling.

Question: If one component of the forest is removed, what would be its affect on the ecosystem?

Answer: Every component of forest depend on other. If we remove one, the other will be affected, e.g. if we remove top carnivores (lion / tiger) in a forest, herbivores will increase and if they increase they will end up eating all plants, so ecosystem will get disturbed.

Question: State the role of scavengers in cleaning of our environment.

Answer: Scavengers eat the dead animals and act as the cleaning agents of our environment. Some of these animals (scavengers) are vultures, crows, jackals, hyena, some insects, etc.

Question: Crown is different from canopy. Explain how.

Answer: The part of the tree with branches is known as the crown. When the crown of tall trees in the forests forms a roof-like covering over the others plants, it is known as a canopy.

Question: “You conserve forest, you conserve soil”. Do you agree? Justify.

Answer: Yes, forests bind soil with root and prevent soil erosion. They also maintain fertility of soil and check So, it can be said that conserving forest results in conservation of soil.

Question: Deforestation can increase the earth’s temperature. Is it true? Give reason.

Answer: Yes, if there are no tress and plants, there will be no photosynthesis. So, no CO2 of the atmosphere will be used. This will increase the level of CO2, resulting in the increase of earth’s temperature.

Question: Explain how root system of plants help in the prevention of flood?

Answer: The root system helps water to seep down in the ground. It helps to maintain the water table throughout the year. Roots of trees normally bind the soil together and stop the erosion of soil.

Question: People say that nothing goes waste in a forest. Can you explain how?

Answer: Nothing goes waste in a forest because of the following reasons

  1. Dry leaves and remains of dead animals are converted to a dark colored substance called humus. This provides nutrients to the plants.
  2. Dead animals become food for vultures, crows, jackals and insects.
  3. Broken branches of trees are used as fuel by the people living in the vicinity of the forest.

Question: “Forest is a dynamic entity, full of life and vitality”. Explain briefly.

Answer: Forests harbor great variety of plants and animals. Plants provide food to herbivores. Larger number of herbivores means increased availability of food for a variety of carnivores. Wide variety of animals helps forest to regenerate.

Decomposers and scavengers are cleaning agents. So, every entity in the forest plays a key and vital role making it a dynamic living entity, full of life and vitality.

Question: Write the major steps by which we can conserve the forest.

Answer: Forests maintain balance in nature. There conservation is the need of the hour. We should take the following steps to conserve the forests

  1. Planned harvesting An efficient way to get wood from forests for our requirements is to cut only some of the trees in an area. The uncut trees prevent erosion. Fruits of these trees produce seeds so that new trees can grow. This way the forest cover is maintained.
  2. Afforestation This is the practice of renewing a forest by planting seedlings or small trees. These days, in our country, planned afforestation is being done not only by the government but also by private organisations for commercial purposes. Selective cutting of trees in these plantations provides wood for construction and also keeps the forest cover intact.
  3. Protection from fire Huge forest areas are destroyed by fire every year. Fire may occur due to the carelessness of people or due to lightning during a storm or by friction between dry stems and dry branches of trees.
    Forest fires are controlled by spraying fire extinguishing solutions from aircrafts or by changing the direction of wind by using strong blowers.

Question: Figure shows a part of a forest.

Write any three activities going on in the forest on the basis of this figure.

Answer: The three activities going on in the forest on the basis of the given figure are

  1. Oxygen is given out by plant leaves.
  2. Carbon dioxide is consumed by the plants to prepare their food by the process of photosynthesis.
  3. Nutrients are being added to the soil by the action of decomposers.

Forests: Our Lifeline NCERT – Question: Cycling of papers help in the conservation of the forests. Justify.

Answer: The papers are made from wood pulp. We derive wood by cutting down trees. If we recycling existing quantity of paper in the market and will not let it decompose, we can stop cutting of forest trees for new raw materials required for paper making.

It takes years to grow a tree and cutting a tree takes only few minutes.

So, we should give a serious thought before cutting a single tree even and should encourage recycling of papers every where in our country and in the world.

Question: Sachin lives in a village, this village is surrounded by a forest. One day he noticed that in nearby pond sedimentation is increased so much that water has become muddy, streams are drying up. There is scarcity of fuel wood. He soon realized that he has to raise the issue of forest protection from cutting down trees, etc. Soon he involved the nearby village people and made an organisation to take an initiative.

Now, answer the following questions

  1. What changes might have Sachin noticed in his area?
  2. Give the probable reason for such changes mentioned above.
  3. What are the values shown by Sachin?

Answer:

  1. Sachin noticed the disturbance in the water cycle in his area like stream drying up. Pond water getting muddy, less availability of fuel wood, etc.
  2. Deforestation.
  3. Love for nature and environmental consciousness.

Question: A snake charmer came to the society and smelled the presence of a cobra near the guardroom. The head of the society agreed to allow the man to search, catch and take away the snake with him. Little Krishi who was seeing all this disagreed. He explained the people that it might disturb the food chain in the environment. Now, answer the following questions

  1. Describe food chain.
  2. Construct a food chain involving snake at one of its level.
  3. What are the values shown by Krishi?

Answer:

  1. The sequence of living organisms in which one organism eats another is called a food chain.
  2. Grass        →       Insect      →       Frog        →        Snake         →          Eagle
    (Producer)    (Herbivore)      (Carnivore)  (Laege carnivore)    (Top carnivore)
  3. Scientific attitude, obligation to maintain the ecosystem of nature.

Fill in the Blanks

  1. The decaying leaves and animal choppings in a forest enrich the ……………… .
  2. Insect, butterflies, honeybees help plants in ……………… formation.
  3. The microorganisms which convert dead plants and animals to humus are called ……………….
  4. Forest is a purifier of ……………… and ……………… .
  5. Herbs form the ……………… layer of the forest.
  6. Forest help in cloud formation as they release ……………… in the air.
  7. The forest are called green lungs because they supply ……………… to the atmosphere.
  8. If there are no plants in the soil, heavy rain will cause extensive soil ……………… .
  9. Different layers provide ……………… and ……………… for animals.
  10. ……………… helps forests to grow and regenerate.

Answer:

  1. soil
  2. seed
  3. decomposers
  4. water, soil
  5. lowest
  6. water vapour
  7. oxygen
  8. erosion
  9. food, shelter
  10. soil

True / False – Forests: Our Lifeline NCERT

  1. 1. Plants are saprotrophs.
  2. Roots of the tree are called crown of the tree.
  3. Plants release C02 in the process of photosynthesis.
  4. Forest is self sustaining entity comprising of plants animals and microorganisms.
  5. Various components of forests are not interdependent on each other.
  6. Forests are lifeline for forest dwelling communities.
  7. we get various products from forests.
  8. Forests protect the soil from erosion.

Answer:

  1. False, plants are autotrophs. They produce their own food by the process of photosynthesis. They are also called producers.
  2. False, the branchy part of part of tree above the stem is known as crown of the tree.
  3. False, plants intake carbon dioxide from the atmosphere during photosynthesis.
  4. True
  5. False, the living organisms founds in the forest are plants, animals and decomposers which are interdependent on each other. As well as non-living environment is also interdependent.
  6. True
  7. True
  8. True

Question: Match the Column I with Column II.

Column I Column II
(a) Humus (i) Depend on plants for food
(b) Forests (ii) Branchy part of the tree
(c) Herbivores (iii) Helps forests to grow
(d) Crown (iv) Dark colored matter
(e) Soil (v) Protect soil from erosion

Answer:

  1. (a) – (iv)
  2. (b) – (v)
  3. (c) – (i)
  4. (d) – (ii)
  5. (e) – (iii)

Question: Match the Columns I with Column II

Column I Column II
(a) Cane (i) Paper
(b) Eucalyptus (ii) Oil
(c) Coniferous trees (iii) Tyres
(d) Rubber tree (iv) Gum
(e) Babool (v) Furniture

Answer:

  1. (a) – (v)
  2. (b) – (ii)
  3. (c) – (i)
  4. (d) – (iii)
  5. (e) – (iv)

Forests: Our Lifeline NCERT – Question: Match the Column I with Column II.

Column I Column II
(a) Decomposers (i) Dead plant and animal tissues
(b) Canopy (ii) Habitats for wildlife
(c) Porcupine (iii) Microorganisms
(d) Humus (iv) Wild animal
(e) Forest (v) Branches of tall trees

Answer:

  1. (a) – (iii)
  2. (b) – (v)
  3. (c) – (iv)
  4. (d) – (i)
  5. (e) – (ii)

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