CBSE Questions for Class 7 Biology Forests Our Lifeline Quiz 1 - MCQExams.com

• Trees help keep soil in place by holding a large amount of soil with there roots.
• Without trees, rain runs off soil into rivers and streams, raising the water level which leads to floods.
  
• Planting trees acts to shield soil from the winds, and the mulch from fallen leaves forms a layer to protect the soil on the "forest" floor.
  
• Hence the forest helps the soil to prevent the flood.
• So, the correct answer is 'Forest'.

• Heavy rainfall leads to flood in towns and villages.
• Drought, volcano and heat waves are the result of lesser rains.
• Hence, Option A is correct.
  

• Forests are reservoirs of wildlife as they provide shelter as well as food to animals. 
• They maintain optimum climatic conditions for the survival of animals. Hence, animals are conserved in wildlife sanctuaries in their natural habitat. 
• Forests also help in raining that make the water available to animals. 
• Hence, the statement given in the question is correct.
  So, the correct answer is 'True'.

• Forests are areas of biodiversity hot spots, as we know. They are full of plants, trees, animals and birds. 
• Even the dead bodies of plants and animals are decayed by saprophytes, supporting large forms of life. 
• In this process, they provide the soil with nutrients that help the seeds to grow properly and support new forms of life. So we can say that forests are dynamic living entities.

• Forests are called green lungs because they fix the carbon dioxide in the presence of sunlight and convert them into glucose by the process of photosynthesis. 
• The reaction of carbon dioxide with water during this process releases oxygen as a byproduct and glucose is formed. Thus, the forest replenishes oxygen in turn of carbon dioxide, which is the basic source of survival of life on earth.
• Forests also have an important role in other bio-cycles such as the water cycle, oxygen cycle, and carbon cycle.

$$\textbf{Correct option: A}$$

$$\textbf{Solution:}$$

Option A:

$$\bullet$$ When we destroy a forest we destroy an ecosystem.

$$\bullet$$ An ecosystem refers to the geographical area where both biotic and abiotic components are present and all biotic components depend on the abiotic components as well as on each other for survival

$$\bullet$$ The biotic components of an ecosystem are living organisms such as plants, animals, microorganisms, etc.

$$\bullet$$ However, water, air, land, soil, atmosphere, etc are the non-living or abiotic components of an ecosystem.

$$\bullet$$ A forest harbors all kinds of living organisms like plants, animals, microbes as well as the abiotic components like water, air, soil, atmosphere, etc.

$$\bullet$$ Thus, destruction of a forest is equivalent to destroying an ecosystem.

Hence the correct option is option A.