Textbook Solution: Our Forests | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

A. Choose the correct option.

1.
Ans: (d)

2.
Ans: (b)

3.
Ans: (d)

4.
Ans: (c)

5.
Ans: (d)

B. Fill in the blanks with correct words.

1. 
Ans: The climate affects the variety of plants and animals found in a region.

2. 
Ans: Roots of plants help to bind the soil particles together and prevent soil erosion.

3. 
Ans: We use dry wood as firewood.

4.
Ans: Eucalyptus provide medicines.

5. 
Ans: When animals die, their bodies are decomposed by fungi.

6. 
Ans: Green plants are called producers because they can make their own food.

7. 
Ans: Large-scale cutting of trees is called deforestation.

C. Write T for true or F for false.

1.
Ans: Trees play a major role in the formation of soil. - True (Because they bind the soil particles together and prevent soil erosion)

2.
Ans: Food chains exist only on land. - False (Because food chains exist everywhere, in water, forests, plains, and even deserts.)

3.
Ans: Plants help to reduce the amount of carbon dioxide in the air. - True (Because they use carbon dioxide for photosynthesis and give out oxygen as a byproduct.)

4.
Ans: Deforestation has led to the destruction of many plants and animals. - True (Because it causes the destruction of the natural habitats of a large number of plants and animals)

5.
Ans: Large-scale cutting of trees is called afforestation. - False (Because large-scale cutting of trees is called deforestation. Afforestation is the large-scale planting of trees to replace the ones that have been cut.)

6.
Ans: We should follow measures to conserve our forests. - True (Because forests are important for the survival of many species, including humans, and they also help in maintaining the balance in the environment.)

D. Answer the following questions.

1.
Ans: Forests are composed of four distinct layers: the emergent layer, canopy, understorey, and ground level. The emergent layer is the uppermost layer, consisting of the tallest trees in the forest. Below this is the canopy, made up of the topmost crowns of slightly smaller trees. These two layers form a dense roof of the forest, receiving the most sunlight, water, and air. The understorey lies beneath the canopy and consists of smaller plants that receive less sunlight and rainfall. The ground level is the forest's lowest layer, composed of the smallest trees, shrubs, dead and fallen foliage, and is home to various microorganisms.

2.
Ans: Trees significantly affect the climate of a place by regulating the amount of rainfall and carbon dioxide levels. They release vast amounts of water vapour into the atmosphere through transpiration, leading to cloud formation and increased precipitation. Trees also absorb carbon dioxide for photosynthesis, which helps lower the carbon dioxide level in the atmosphere, preventing global warming.

3.
Ans: The coconut and palm trees act as windbreakers. They help break the force of strong winds, especially in coastal areas, thereby preventing potential damage.

4.
Ans: Forests play a crucial role in our daily lives. They prevent soil erosion, help in regulating climate by increasing rainfall and reducing carbon dioxide levels, and act as windbreakers. Forests provide timber and fuel wood for various industries like furniture, paper, and pulp. We also get food items, essential oils, latex for rubber, resins for paints from forests. Several medicines are derived from forest plants like neem, eucalyptus, amla, and Cinchona. They also provide food and shelter to a variety of animals.

5.
Ans: A food chain is a linear sequence showing which organism is eaten by whom. It starts with producers (plants) and ends with the topmost consumers. A food web, on the other hand, is a complex network of interconnected food chains. It represents multiple pathways through which energy and matter flow in an ecosystem.

6.
Ans: A food chain is a linear sequence of organisms where each organism feeds on the one before it. Energy flows through different levels in a food chain, starting from producers (plants) to consumers (animals). The energy decreases as it moves up the food chain.

7.
Ans: In a forest, plants and animals exhibit a high degree of interdependence. Animals depend on plants for food and shelter, while plants rely on animals for pollination and seed dispersal. When plants and animals die, decomposers like bacteria and fungi break them down into simpler substances that get absorbed into the soil, which in turn is used by other plants.

8.
Ans: Forests reduce the carbon dioxide content of the atmosphere by taking up large amounts of carbon dioxide for photosynthesis. This process helps to prevent global warming.

9.
Ans: Deforestation is the large-scale cutting of trees for various purposes like development, housing, agriculture, and timber. Its consequences include changes in climate, decrease in rainfall, destruction of natural habitats leading to extinction of species, and natural disasters like floods and landslides.

10.
Ans: Four ways to conserve our forests include afforestation (planting of trees on a large scale), planned cultivation (preventing clearing of forests for agricultural lands), preventing illegal felling of trees for timber, and preventing overgrazing by cattle. Additionally, spreading awareness about human activities that may cause forest fires can help in forest conservation.