(a) Deforestation: The cutting down of trees for commercial purposes is called Deforestation.
(b) Deforestation affects wild animals and human beings
(1) In absence of plants, the animals will not get food and shelter.
(2) In absence of plants, carbon dioxide in air will increase resulting in increase in Earth's temperature.
(3) In absence of plants, soil will not hold water, which will cause floods.
(4) Deforestation will endanger our life and environment.

The trees have crowns of different sized and types. These create different horizontal layers in the forest. These are known as understoreys. Giant and tall trees constitute the top layer followed by shrubs and tall grasses and herbs form the lowest layer.

Seeds produced by forest trees are dispersed to long distance by wind and animals. When they get suitable condition they germinate and turn seedling and then saplings.

In nature herbs are eaten by herbivore, in turn herbivores are eaten by carnivores. This sequence of eating and being eaten, forms a chain called food chain.
Example:
Grass ⇾ Insect ⇾ Frog ➝ Snake ⇾ Eagle

Trees and other plants in a forest consume carbon dioxide during the process of photosynthesis and release O₂ to maintain the balance in amount of CO₂ and O₂.

Sal, teak, semal, neem, amla, bamboo, palash (any four).

Forests are called green lungs as they maintain the balance of oxygen and carbon dioxide. Carbon dioxide given out by animals during respiration is used by forest trees in photosynthesis resulting in release of oxygen. Hence, forests are known as green lungs.

(i) If forests disappear, the quantity of carbon dioxide in air will rise, leading to the increase in earth's temperature.
(ii) In the absence of trees and plants, the animals will lack food and shelter.
(iii) In the absence of trees, the soil will not hold water, this will cause floods.
(iv) Deforestation is a menace to our life and environment.

There will be water logging or even flood. Everything will be water logged. No food, no water. No room to sleep. no traffic.

Humus is found in the top layer of soil. The presence of humus ensures that the nutrients of the dead plants and animals pass into the soil. From there, these nutrients are again absorbed by the roots of the living plants.

No, because of varying climatic conditions there are variations in the types of trees and other plants. The type of animals also vary from forest to forest.

A typical food chain in a pond is Algae ⟶ Small fishes ⟶ Large fishes.

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

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.

Boars, bisons, jackals, porcupines, elephants, etc., live in the deeper areas of the forest.