2 Marks Questions - Science STD 7 Questions - Vidyadip

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26 questions · timed · auto-graded

Question 12 Marks

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 realised that he has to raise the issue of forest protection from cutting down trees, etc. Soon he gathered the nearby village people and made an organisation to take an initiative.
Now, answer the following questions
(i) What changes might have Sachin noticed in his area?
(ii) Give the probable reason for such changes mentioned above.

Answer

(i) Sachin noticed that pond sedimentation is increased and water became muddy.
(ii) The probable reasons for such change are as follows
(a) Deforestation
(b) Soil erosion

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Question 22 Marks

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. She explained the people that it might disturb the food chain in the environment. Now, answer the following questions.
(i) Describe food chain.
(ii) Construct a food chain involving snake at one of its level.

Answer

(i) A food chain is the sequence of events in an ecosystem where one organism consumes another and then that organism is consumed by another larger organism.
(ii) Plant → Grasshopper → Frog → Snake → Hawk

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Question 32 Marks

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
(i) Construction of roads.
(ii) Construction of buildings.
(iii) Industrial development.
(iv) Increasing demand of wood.

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Question 42 Marks

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.

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Question 52 Marks

What would happen if forests disappear?

Answer

If forest disappear following consequences can occur
(a) If the forest disappear, the amount of carbon dioxide in air will increase, resulting in the increase of Earth's temperature.
(b) In the absence of trees and plants, the animals will not get food and shelter.
(c) In the absence of trees, the soil will not hold water, which will cause floods.
(d) Deforestation will endanger our life and environment.

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Question 62 Marks

If there were fewer trees, how will the water cycle be affected?

Answer

If there are less number of trees then there would be less evaporation from plants and consequently less water vapour in the air. This would lead to fewer clouds. Hence, there would not be much rain. So the presence of fewer trees affects the water cycle.

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Question 72 Marks

In which layer of the soil would you find humus? What is its importance to the soil?

Answer

A layer of humus is found on forest floor or topsoil layer. It ensures that the nutrients of the dead plants and animals are released into the soil.

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Question 82 Marks

Paheli asked. "There are so many trees here. Also, there are many forests like this. What difference will it make if we cut some trees for a factory"?

Answer

Green plants produce food. All animals whether herbivores or carnivores, depend ultimately on plants for food. Organisms which feed on plant often get eaten by other organisms. Every part of the forest is dependent on the other parts. If we remove one component, e.g. trees, all the other components would be affected.

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Question 92 Marks

Would we see similar kind of trees in every forest? Asked Boojho'.

Answer

No, we would not see similar kind of trees in every forest. Due to different climatic conditions there are variations in the types of trees and other plants. The types of animals also differ from forest to forest.

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Question 102 Marks

Deforestation can increase the Earth's temperature. Is it true? Give reason.

Answer

Yes, if there are no trees and plants, there will be no photosynthesis. Thus, no CO₂ of the atmosphere will be used. This will increase the level of CO₂ in the atmosphere, resulting in the increase of Earth's temperature.

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Question 112 Marks

Forests are considered as the most 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. Thus, forests are the most valuable resources.

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Question 122 Marks

"You conserve forest, you conserve soil". Do you agree? Justify.

Answer

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

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Question 132 Marks

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

Answer

The roots of the trees hold the topsoil and make it porous which allows rainwater to seep through it. Thus, forests help to reduce flood by absorbing excess rainwater and slowing down water flow.

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Question 142 Marks

Forests are called green lungs. Why?

Answer

Forests are called green lungs because they play a crucial role in maintaining the balance of the environment by providing oxygen and removing carbon dioxide.

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Question 152 Marks

Sketch a diagram to show how plants maintain the balance between carbon dioxide and oxygen in the atmosphere?

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Question 162 Marks

Write differences between decomposers and scavengers.

Answer

Differences between decomposers and scavengers is as follows

Decomposers	Scavengers
These are the microbes which break dead organic matter into simple molecules which are used by plants again, e.g. fungi, millipedes are decomposers, etc.	These animals eat the body of dead animals and are called cleaning agent of forests, e.g. jackal, fox, vulture, etc.

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Question 172 Marks

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

Answer

Every component of forest depend on each other. If we remove one component 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.

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Question 182 Marks

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 the process called photosynthesis and provide food to all living organisms which live in the forest.

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Question 192 Marks

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.

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Question 202 Marks

"Forest is a dynamic entity, full of life and vitality". Explain briefly.

Answer

Forests harbour great variety of plants and animals. Larger number of herbivores means increased availability of food for a variety of carnivores. Wide variety of animals helps forest to regenerate and grow. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. So, every entity in the forest plays a vital role making it a dynamic living entity, full of life and vitality.

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Question 212 Marks

In figure, the artist has forgotten to put the labels and directions on the arrows. Mark the directions on the arrows and label the diagram using the labels clouds, rain, atmosphere, carbon dioxide, oxygen, plant, animal, soll, roots, water table.

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Question 222 Marks

Explain why there is a need of variety of animals and plants in a forests.

Answer

By harbouring greater variety of plants, the forest provides great opportunities of food and habitat for the herbivores. Larger number of herbivores means increased availability of food for a variety of carnivores.
The wide variety of animals helps the forest to regenerate and grow. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the forest is a dynamic living entity, i.e. full of life and vitality. There is a continuous interaction between soil, water, air, plants and animals in a forest.

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Question 232 Marks

Explain why there is no waste in a forest?

Answer

There is no waste in a forest because microorganisms act on the waste and convert into humus. The humus ensures that the nutrients are returned back to the soil.

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Question 242 Marks

What are decomposers? Name any two of them. What do they do in the forest?

Answer

Decomposers are the microorganisms that convert the dead plants and animals into humus. Bacteria and mushroom are the examples of decomposers.
They help in the process of recycling of nutrients by decomposing various dead organisms such as plants and animals to form humus. Therefore, decomposers are helpful for the environment.

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Question 252 Marks

Write the importance of bacteria in the forest ecosystem.

Answer

They act as decomposers and break down dead plants and animals into simpler substances.They return nutrients to the soil, increasing soil fertility and helping plants grow.

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Question 262 Marks

The decaying matter is always moist and warm. Explain why?

Answer

Decomposers like bacteria and fungi break down dead plants and animals, and they require moisture to survive and carry out decomposition.During decomposition, heat is released due to biological activity, which makes the decaying matter warm.

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2 Marks Questions - Science STD 7 Questions - Vidyadip