# NCERT Class 10: Science-Intext Solutions

### Chapter 15-Our Environment-Intext Solutions

NCERT Book Page Number-260
Q.1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Ans. The various links or steps in a food chain at which the transfer of food and energy takes place are called trophic levels.
The producers form the first trophic level as they manufacture food. The primary consumers form the second trophic level, the secondary consumers form the third, and the tertiary consumers form the fourth trophic level.
Grass is the producer which is eaten by the grasshopper known as primary consumer. Then the grasshopper is eaten by shrew (secondary consumer) and lastly shrew is eaten up by owl (tertiary consumer).
Q.2. What is the role of decomposers in the ecosystem ?
Ans. Various roles played by decomposers in the ecosystem are:
• They clean the environment.
• They decompose biodegradable substances into useful substances.
• They release nutrients into soil by decomposing dead and decaying matter, thus making the soil fertile.
• They maintain the nutrient pool by returning back the nutrients in the pool.

NCERT Book Page Number-262
Ans. Substances are classified as biodegradable and non-biodegradable because some substances can be decomposed by microorganisms and some cannot.
Substances that are broken down into simple soluble forms are called biodegradable substances and the substances that are not decomposed by microorganisms into harmless substances are called non biodegradable substances.
Q.2. Give any two ways in which biodegradable substances would affect the environment.
Ans. Biodegradable substances affect the environment by:
(a) The biodegradable substances such as tree leaves, plant parts, and kitchen wastes can be used as humus after composting. This will enhance the soil fertility.
(b) The biodegradable substances mainly contain carbon. These substances after decomposi¬tion release that carbon back into the atmosphere.
Q.3. Give any two ways in which non-biodegradable substances would affect the environment.
Ans. Non-biodegradable substances affect the environment by:
(a) They contaminate soil and water resources as they cannot be decomposed by microorganisms.
(b) These substances, when accidentally are eaten by stray animals, can harm them and can even cause their death.

NCERT Book Page Number-264
Q.1. What is ozone and how does it affect any ecosystem?
Ans. Ozone $(O_{3})$is a molecule, made up of three atoms of oxygen. Ozone $(O_{3})$ forms a layer in the upper atmosphere. It is very essential for the life on this planet. It shields the surface of the earth from ultra-violet radiation (UV) coming from the sun as these radiations are very harmful may cause skin cancer and cataract in humans. They also harm the crops.

Q.2. How can you help in reducing the problem of waste disposal? Give any two methods.
Ans. We can help in reducing the problem of waste disposal by these methods: