Page 156 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

it prevents sunlight from reaching the layers and floor beneath. It receives a fair

amount of sunlight and rain. This layer has plentiful supply of fruits and nuts which

is why abundant wildlife can be found in this layer as compared to any other layer in
the forest.

5. What do you mean by food web? Give an example.

Ans: Food Web : In environment, each organism is not restricted only to one food
chain, rather it can be a part of a number of food chains. Several food chains can

be interlinked. This interwoven network of several interconnected food chains in a

community is called a food web.
Plants are eaten by zebras, grasshoppers, deer, rabbits and so on. These herbivores

then become food for carnivores such as lions and tigers. Rabbits can also be eaten

by owls, snakes and lions, while snakes can be eaten by vultures, eagles and so on.
6. How do forests play an important role in our lives?

Ans: Forests play an important role in our lives as follows:

• Firewood and dry leaves are used as kitchen fuel in villages, which are located

near the forests.
• Forests prevent soil erosion and help in soil conservation.

• Forests are the primary source of food for all living beings, as all creatures,

whether big or small, depend directly or indirectly on plants for food.
• The roots of trees and plants in forests allow greater infiltration into the soil,

preventing floods and droughts.

• Green plants take in carbon dioxide and release oxygen, thereby maintaining
the levels of these gases in the air.

• They help in bringing rains and maintaining the water cycle in the atmosphere.

• They serve as a place of recreation and tourism.

7. What is humus?
Ans: The decayed and decomposed plant or animal matter converts into an organic

substance known as humus that adds the required nutrients to the soil and makes it

fertile.
8. What are trophic levels?

Ans: Trophic levels are the various steps or levels in a food chain or a food web where

transfer of food or energy takes place. Energy is transferred from the lower trophic
level to the higher level.

156