#In-text Questions solutions-
Q1- Why are some substances biodegradable and some non-biodegradable?
Ans. Those wastes which can be degraded by biological or microbial actions are called biodegradable wastes e.g. domestic sewage, livestock wastes, municipal wastes, etc., while those wastes which are not acted upon by the microbes or acted upon very slowly, so cannot be decomposed, are called non-biodegradable wastes e.g. plastic wastes, pesticides, polyethylene bags, synthetic polymers, etc.
Q2- Give any two ways in which biodegradable substances would affect the environment.
Ans. (i) These cause pollution when they are added in more amounts than their rate of degradation.
(ii) Accumulation of biodegradable organic wastes in the water bodies, causes deoxygenation of water and killing of aquatic organisms.
(iii) Decomposition of organic solid wastes produces obnoxious gases which causes air pollution.
Q3- What is ozone and how does it affect any ecosystem?
Ans. Ozone (O3) is a molecule formed by three atoms of oxygen.It is a poisonous gas for the living organisms, but plays a significant role in the biosphere. Ozone forms a radiation belt, called ozonosphere, in the stratosphere of atmosphere and absorbs the harmful UV-radiations of the sunlight. It is very important for the survival and existence of life on earth.
Q4- Give any two ways in which non-biodegradable substances would affect the environment?
Ans. (i) Non-biodegradable solid wastes may choke the drains resulting in water logging, which in turn results in breeding of the mosquitoes and increases the chances of spread of malaria, filariasis, dengue, etc.
(ii) Biomagnification of pesticides like DDT interferes with the formation of egg-shell in the birds. The egg shells remain thin and break during incubation.
Q5- What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Ans. (i) The organisms deriving their energy from the same source belong to the same trophic level.
(ii) Example: A food chain of pond ecosystem has following trophic levels:
Food chain: Phytoplanktons- Zooplanktons-Small fish-Large fish- predatory birds
Q6- What is the role of decomposers in the environment?
Ans. Decomposers are those microconsumers, which break down the complex organic compounds of dead bodies of both plants and animals and release inorganic compounds into the environment from where they are reused by the producers. These help in material cycling. Decomposers include bacteria and fungi.
Q7- How can you help in reducing the problem of waste disposal?Give any two methods.
Ans. (i) Segregation of different types of waste materials for their separate treatment
(ii) Biodegradable wastes can be disposed off by composting ( conversion of wastes into humus).
(iii) Non-biodegradable wastes can be disposed off by incineration (aerobic burning of solid wastes at high temperature) or pyrolysis (anaerobic burning of solid wastes at high temperature) or land filling.
NCERT Solutions for Class 10 Science Chapter 15: Our Environment