Class 10 Science

Our Environment NCERT Exemplar Problem

Long Answer Type Questions

Question 31: Indicate the flow of energy in an ecosystem. Why is it unidirectional? Justify.

Answer: The flow of energy in an ecosystem happens in following sequence:

Producer ↠ Primary Consumer ↠ Secondary Consumer ↠ Tertiary Consumer

The flow of energy is unidirectional in the food chain due to two reasons. A predator always eats its prey but other way round is not possible. Moreover, out of the total energy consumed by an organism at a particular trophic level; 90% is utilised for its own need and just 10% is left for the organism of next trophic level. Thus, the availability of energy gets reduced at subsequent trophic level. Due to this, the flow of energy is unidirectional in a food chain.

Question 32: What are decomposers? What will be the consequence of their absence in an ecosystem?

Answer: Organisms which decompose the dead remains of plants and animals are called decomposers. Bacteria and fungi play the role of decomposers.

Decomposers decompose dead remains of plants and animals. By doing so, they serve two purposes. One; they reduce the burden on the environment by clearing dead remains. Two; they channelize the raw materials back to the environment.

Hence, if there were no decomposers in the environment it would lead to accumulation of dead plants and animals in the environment. Additionally, the environment would be finally sapped of all its resources which are needed to maintain and sustain life.

Question 33: Suggest any four activities in daily life which are eco-friendly.

Answer: Four eco-friendly activities in daily life:

  1. Walking and cycling for commute.
  2. Using jute/cloth shopping bag.
  3. Using public transport.
  4. Switching off light/fans in unoccupied rooms.

Question 34: Give two differences between food chain and food web.


Food chainFood web
It is a simple chain, involving a handful of organisms.It is a complex web of many interconnected food chains, involving many organisms.
There is usually a single organism at a particular trophic level.There are more than one organism at a particular trophic level.
Food chain is a hypothetical situation.Food web is real life situation.

Question 35: Name the wastes which are generated in your house daily. What measures would you take for their disposal?


WasteMeasures for disposal
Vegetable/fruit peels/Stale foodKeep in garbage bins and give to sanitation workers who come to collect garbage.
Plastic bagsShould be dumped in garbage bins which are meant for non-biodegradable materials.
Old newspapersShould be sent for recycling.

Question 36: Suggest suitable mechanism (s) for waste management in fertiliser industries.

Answer: Effluents and harmful gases are the main wastes which are produced in a fertiliser factory.

Treatment of Polluting Gases: For reducing the amount of gaseous pollutants, catalytic converters should be fitted in the chimneys.

Effluent Treatment: Effluent from the factory should be sent to effluent treatment plant. Sedimentation, flocculation, filtration and chlorination are various steps of effluent treatment. Once effluent is treated, then clean water can be sent to the nearest water bodies. The sludge can be allowed to decompose which can later be used as manure.

Question 37: What are the by-products of fertiliser industries? How do they affect the environment?

Answer: The by-products of fertiliser industries are oxides of sulphur and nitrogen, some solid waste and some other chemiclas. When oxides of sulphur and nitrogen get mixed with rainwater, then acid rain is formed. Acid rain is harmful for plants and animals. It also harms historic monuments.

Question 38: Explain some harmful effects of agricultural practices on the environment.

Answer: Some of the harmful effects of agricultural practices on the environment are as follows:

Climate Change: As farming means growing a selected number of species on a large tract of land, it promotes monoculture. Thus farming affects the biodiversity of a region in a negative way.

Deforestation: Clearing of forests for agriculture has resulted in loss of habitat to wildlife. Deforestation has also affected the natural recharge process of groundwater.

Soil degradation: Intensive farming robs off the soil of its nutrients. In the long run, it can lead to soil erosion and finally to desertification.

Water shortage: Overexploitation of groundwater for irrigation has resulted in acute water shortage at many places.

Pollution: Use of synthetic fertilisers and pesticides creates soil pollution, water pollution and air pollution.