NCERT Class X Science Class: Chapter – 15. Our Environment – Part-6 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 34:

Give two differences between food chain and food web.


Food Chain and Food Web
BasisFood ChainFood Web
DefinitionThe flow of energy through a single and straight pathway from the lower trophic level to the higher trophic level is known as food chain.The interconnected, numerous food chains through which the energy flow in the ecosystem is known as food web.
StabilityThe instability increases due to the increasing number of separate and confined food chains.Stability increases due to the existence of the complex food chains.
Number of chainsIt consists of only one straight chain.It consists of many interconnected food chains.
Feed uponMember of higher tropic level depends upon the single type of organisms of the lower tropic level.Members of higher tropic level depend upon many different types of the organism of the lower tropic level.
Disturbances arise due toif one group of an organism disturbs, the whole chain will be disturbed.The food web doesn՚t get disturbed by the disturbance of one group of organisms.
Types1. Grazing food chain. 2. Detritus food chain.No type
Trophic levelConsists of 4 - 6 tropic levels of different species.Contains numerous tropic level also of different populations of species.

Question 35:

Name the wastes which are generated in your house daily. What measures would you take for their disposal?


(a) Kitchen wastes

(b) Paper wastes like newspapers, bags, envelopes

(c) Plastic bags

(d) Vegetable/fruit peels/rind

Measures for disposal

(a) Segregation of biodegradable and non-biodegradable wastes.

(b) Safe disposal of plastic bags.

(c) Vegetable/fruit peels can be placed near trees/plants, which on decomposition will enrich the soil with nutrients.

(d) Give paper wastes for recycling.

(e) Prepare a compost pit for kitchen wastes

Question 36:

Suggest suitable mechanism (s) for waste management in fertilizer industries.


Fertiliser industries produce mainly two types of wastes (a) Gaseous, (b) Effluents. Additionally they may release heat and fuel waste of coal is being used as a source of energy.

1. Gaseous wastes: They are passed through wet scrubbers to dissolve the pollutant gases.

2. Effluents: The effluents of the industry are tested for chemicals present in them. The same can be retrieved and made available to the market. Hot effluents are cooled. Acidic or alkaline nature can be correct. Heavy metals and toxins can be separated. Only treated and harmless effluents are allowed to be discharged into surrounding environment.

Question 37:

What are the by-products of fertilizer industries? How do they affect the environment?


The by products of the fertilizer industries are:-

  1. Gases-
  2. Solids- Pyrite ashes, Calcium Carbonate, sand and plastic bag. Effect on Environment.

The majority of the gaseous by products like carbon dioxide, methane are green house gases which contribute to global warming. Rest of the gases like sulphur dioxide and nitrous oxide are air pollutants and lead to acid rain. These gaseous by products cause breathing and respiratory problem.

The solid waste and waste water discharges into the water body. When these wastes are discharged in the water body they increase the nutrient content of the water and cause algal bloom (increase in number of algae) . Due to algal bloom, algae forms a layer on the surface of the water and hence the oxygen does not reach the water body and all the fishes and water animals are killed.

Question 38:

Explain some harmful effects of agricultural practices on the environment.


(a) Excessive use of fertilisers changes the chemistry of soil and kills useful microbes.

(b) Excessive use of non-biodegradable chemical pesticides leads to biological magnification.

(c) Extensive cropping causes loss of soil fertility.

(d) Excess use of ground water for agriculture lowers the water table.

(e) Damage to natural ecosystem/habitat.

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