The root system helps water to seep down in the ground. It helps to maintain the water table throughout the year. Roots of trees normally bind the soil together and stop the erosion of soil.

The given figure completely explains the exchange of gases between plants and animals.

(i) Fruits
(ii) Vegetables
(iii) Medicines
(iv) Oxygen
(v) Cereals

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

The animals in forests are of various types. These could be herbivores, carnivores, microorganisms, etc. These play an important role in maintaining the food chains.
(i) Microorganisms convert the dead plants and animals into humus. This humus helps in returning the nutrients back to the soil. These are absorbed by plants.
(ii) The animals also help in dispersing the seeds of certain plants.
(iii) The decaying animal dung provides nutrients.
All these activities of animals dwelling in the forest help it to grow and regenerate.

Deforestation leads to floods as lesser number of trees will be available due to deforestation. In the absence of trees, the soil will not hold water leading to floods.

Four useful products other than wood which we get from forests are gum, spices, fodder for animals and medicinal plants.

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

The variation in the type of plants and animals is found in different forests because of the climatic conditions of that particular area.

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

(a) Sachin noticed the disturbance in the water cycle in his area like stream drying up. Pond water getting muddy, less availability of fuel wood, etc.
(b) Deforestation.
(c) Love for nature and environmental consciousness.

Nothing goes waste in a forest because of the following reasons
(i) Dry leaves and remains of dead animals are converted to a dark coloured substance called humus. This provides nutrients to the plants.
(ii) Dead animals become food for vultures, crows, jackals and insects.
(iii) Broken branches of trees are used as fuel by the people living in the vicinity of the forest.