NCERT Science Class 10 Chapter 14 Our Environment CBSE Board Sample Problems Long Answer

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Question

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Solution

  • Biological magnification is defined as the accumulation or increase in the concentration of some toxic substances in the body of living organisms at each trophic level of a food chain.

  • The levels of bio magnification will be different at different trophic levels because the animals at the highest trophic level or at the extreme right side of the food chain will have the maximum concentration of harmful chemicals in the body, and grass which is at the lowest trophic level will have minimum concentration of harmful chemicals.

  • Grass (Absorbs chemicals from soil) -Goat (Receives chemicals from fodder) - Humans

  • (Receives chemicals from milk/meat)

Question

What are the different methods of waste disposal?

Solution

Methods of waste disposal are as follows

  • Biogas plant: Biodegradable waste can be used in biogas plant to produce biogas and manure.

  • Sewage treatment plant: The drain water can be cleaned in sewage treatment plant before adding it to rivers.

  • Land fillings: The wastes are buried in low lying areas and are compacted by rolling with bulldozers.

  • Composting: Organic wastes are filled in a compost pit and covered with a layer of soil, after about three months garbage changes to manure.

  • (y) Recycling: Non-biodegradable wastes are recycled to make new items.

  • Reuse: It is a conventional technique to use an item again.

  • Example: newspaper for making envelopes.

Question

a) “Vegetarian food habits can sustain a larger number of people.” Justify the statement in terms of food chain.

Solution

  • Vegetarian food habits involve two step food chain. I.e. producers to herbivores.

  • According to 10% law energy flows from one trophic level to another. So vegetarians get more energy than non-vegetarians.

  • More energy in the producer plants can feed larger number of people thus, vegetarian food habits can sustain a larger number of people.

Question

State one important function of ozone layer in the atmosphere. How is it formed there? Which compounds are responsible for the depletion of ozone layer? How do these compounds enter into the atmosphere?

Solution

  • Ozone present the upper regions of the atmosphere protects us from dangerous UV radiations.

  • Formation of ozone layer:

  • Ozone at the higher levels of the atmosphere is a product of UV radiations acting on oxygen () molecule.

  • The higher energy UV radiations split a part some molecular oxygen () into free oxygen (O) atoms.

  • These atoms then combine with the molecular oxygen to form ozone as shown:

  • Chlorofluorocarbons (CFCs) are responsible for the depletion of ozone layer.

  • These compounds enter the atmosphere when aerosols, refrigerators and fire extinguishers are used.

Question

List three environmental friendly practices which you would like to form a part of your daily habits giving justification for each.

Solution

Three environmental friendly activities are:

  • Should walk short distance to reduce use of vehicle running on fossil fuels.

  • Use both sides of papers to reduce it suse. Less trees will be cut to make more paper.

  • Packing the gifts should not be practiced. It will reduce the use of shiny but non- biodegradable packing paper. Instead use the boxes and envelopes in which the gifts was received

Question

Monika was observing a lizard on the wall which chased an insect and ate it. She felt that lizard is cruel and ugly. Suddenly the lizard fell and was eaten by a cat.

She started thinking, how organisms are connected to each other for their food?

What is a food chain? Will the world be a better place without lizards?

Make a food chain of five organisms.

To which trophic level does the lizard belong?

Solution

  • Food chain is a sequence of who eats whom in an ecosystem.

  • No, lizard s are a part of many food chains.

  • Without them food chain will be disrupted.

  • Grass -grass hopper - frog -snake-peacock.

  • Third trophic level/Secondary consumer/ small carnivore

Question

Differentiate between autotrophs, heterotrophs and decomposers and give one example of each

Solution

  • Autotrophs are the organisms that can make their own food from carbon dioxide and water under the action of sunlight and in the presence of chlorophyll.

  • Example: All green plants.

  • Heterotrophs are the organisms which cannot make their own food by the process of photosynthesis and are dependent on others for food.

  • Example: All animals c. Decomposers are the organisms that de compose the complex molecules present i n the dead remains of plants and animals. Example: Bacteria Fungi