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NCERT Solutions for Class 10 Science Chapter 15
Class X Science – Our Environment
Important Questions with Answers for CBSE Board – 2018
What are two components of our environmental?
(i) Biotic components: Plants and animals.
(ii) Abiotic components: Air, water, soil etc.
Distinguish between biodegradable and non-biodegradable substances. List two effects of each of them on our environment.
(i) They can be broken into simplest form by biological processes.
(ii) They do not produce more pollution.
(iii) They remain for less time in environment.
(i) They cannot be broken by biological processes.
(ii) They produce more pollution.
(iii) They remain for a long time in the environment.
Effect of biodegradable substances:
(i) They release harmful gases like methane.
(ii) They release foul smell.
Effect of non-biodegradable substances:
(i) They are very harmful for the various member of the ecosystem.
(ii) They cause more pollution of air, water and soil.
What is an Eco-system?
Eco-system is the whole biotic community (living organisms) in a given area plus its abiotic environment (physical factors like temperature, rainfall, wind, soil and minerals) both interacting with each other and maintain a balance in nature. Eco-system can be as large as a forest, or small as a pond or lake. This functional system may be natural as forest or may be artificial (man-made), e.g., a crop field or an aquarium. Thus the Eco-system has biotic and abiotic components.
Why is energy flow in the biosphere unidirectional?
The sun is the only source of energy which plants trap during photosynthesis and store as food. The transfer of energy from one trophic level to the other obeys 10% law, i.e., 90% of energy is lost as heat. The energy in the form of heat goes unutilised because plants cannot use this heat energy in the synthesis of food. Thus, there is always flow of energy from the non-living component (then sun) and is released as heat. So, the energy flow in the biosphere is unidirectional.
Why is food chain having two steps most advantageous in terms of energy?
There will be maximum energy transfer from producer to the primary consumer (herbivores). These will least loss of the energy trapped by plant, as heat in transfer.
Explain the phenomenon of “biological magnification”. How does it affect organisms belonging to different trophic levels particularly the tertiary consumers?
When any harmful chemical like DDT, BHC enters in a food chain the concentration of chemical increases as the trophic level is increased (i.e., next higher level). The phenomenon is called biological magnification.
These chemical, get accumulated progressively at each trophic level. It is maximum at the top (highest) trophic level. The tertiary consumers occupy the top trophic level (in most of the food chains) so there is maximum concentration of the harmful chemicals ant they are affected badly.
The flow of energy in food chain is unidirectional. Why?
The flow of energy in a food chain follows 10% law. The energy used or lost in environment as heat, cannot enter at any trophic level in the food chain. Only solar energy can enters in the food chain at producer level and ultimately get lost as heat.
How is the increase in demand for energy affecting our environment adversely?
The demand of energy as increased it has led to utilization of non-renewable resources of energy at a faster rate. Due to which an imbalance is created in our environment, It also led to pollution at a large scale.
What is ozone and how it affect any Eco-system?
Ozone(O3) a molecule formed by three atoms of oxygen. It is a deadly poisonous gas. However, at the higher level of atmosphere, it performs an essential function. It shields surface of earth from ultraviolet radiation (UV) of solar radiations. This radiation is highly damaging to organisms, it is known to cause skin cancer, cataract in human beings.
Mention one negative effect of our affluent life style on the environment.
Excessive use of fossil fuel, even when we have to go nearby we use car, motor cycle, etc. instead going on foot or by cycle. Fossil fuels, on burning produce oxides of carbon, nitrogen and sulphur which cause air pollution.