CBSE Class 10 Science Our Environment Worksheet

Question. What is a food web? Give few characteristics of a food web? Give an example of a food web?
Answer: Food web is a network of food chains which become interconnected at various trophic levels so as to form a number of feeding connections amongst different organisms of a biotic community.
Some characteristics of a food web are:
(a) Food web is an interlink of different food chains.
(b) It provides alternative pathways of food availability.
(c) Due to greater alternatives for food, it makes the ecosystem stable.
(d) It helps in development of an ecosystem.
Example of food web: 

Question. Describe how decomposers facilitate recycling of matter in order to maintain balance in the ecosystem?
Answer: Decomposers act upon dead and decay organisms to convert them into simpler forms. These simple substances get mixed up in the soil and are used as nutrients by the producers. From producers it goes to consumers and so on. Thus there is recycling of matter which is done by decomposers that maintain
the balance in the ecosystem.

Question. Define a food chain. Design a terrestrial food chain of four trophic levels. If a pollutant enters at the producer level, the organisms of which trophic level will have the maximum concentration of the pollutant in their bodies? What is this phenomenon called?
Answer: It is the sequence of arrangement of living organism in a community in which one organism consumes another organism to transfer food energy. 

The organism at higer tropic level will have the maximum concentration of pollutants. This phenomenon is called biological magnification.

Question. Give any two ways in which biodegradable substances would affect the environment.
Answer: The two ways in which biodegradable substances would affect the environment are:
(a) Decomposition of biodegradable substances results in production of foul smell.
(b) The area where biodegradable wastes are accumulated serves as a good breeding place for mosquitoes, flies etc.
which are the main carriers of germs for diseases like cholera, jaundice, typhoid etc.

Question. Give some characteristics of a food chain?
Answer: Some characteristics of food chain are:
(a) A food chain always progress in a straight chain.
(b) There is an unidirectional flow of energy from sun to producers to a series of consumers.
(c) There are 3-4 trophic levels or maximum upto 5 levels in a food chain.
(d) It helps in understanding the food relationships and interaction among various living organisms present in an ecosystem.

Question. Briefly describe different methods of wastes disposal?
Answer: The various methods of waste disposal are:
(a) Land-fills: In urban areas wastes are filled or deposited in low lying areas. These are also known as dumping grounds where wastes are buried.
(b) Recycling of wastes: Some wastes like papers, plastics, metals etc., which can be recycled are send to special recycling treatment plants so that new substances can be made from them.
(c) Preparation of compost: Biodegradable wastes like kitchen wastes, peels of fruits and vegetables etc., can be used to prepare compost which serves as a good manure to the plants.
(d) Incineration: Some wastes like medical wastes, chemical wastes are burnt at very high temperature in an incinerator and the ashes left behind are disposed by landfills.
(e) Production of biogas: Biodegradable wastes can be used in biogas plants to produce biogas which is used for several purposes like as a fuel.

Question. If all the waste we generate is biodegradable, will this have no impact on the environment? 
Answer: If all the waste we generate is biodegradable then their decomposition at right time will not be possible as number of decomposers would be less as compared to the amount of biodegradable substances. It will get accumulated in the environment causing foul smell and will form a good breeding place for flies, mosquitoes etc., which will carry many disease
causing germs. Thus various diseases like cholera, typhoid, jaundice, malaria, dengue etc., will be spread

Question. Suggest any four activities in daily life which are ecofriendly?
Answer: The four activities in daily life which are ecofriendly are:
(a) Carrying paper bags instead of polythene bags for shopping.
(b) Use of compost and biofertilisers, biopesticides instead of chemical fertilisers and pesticides.
(c) Segregating biodegradable and non-biodegradable substances and putting them in separate dustbins.
(d) Rain water harvesting.

Question. Define an ecosystem. Draw a block diagram to show the flow of energy in an ecosystem.
Answer: Ecosystem refers to the interaction of all the biotic and abiotic components present in a particular area. Energy flows across the trophic levels following the 10% law. Only 10% of the energy, available to a trophic level is passed on to the next trophic level. 

Question. What are the problems caused by the non-biodegradable wastes that we generate? 
Answer: The problems caused by the non-biodegradable wastes are:
(i) mulate in the soil causing pollution and also reduces the fertility of the soil.
(ii) Some pesticides like DDT, mercury etc., which are nonbiodegradable undergo biological magnification by entering into food chain.
(iii) If these substances do not undergo proper disposal techniques they will accumulate in soil thus reduces the fertility of soil.
(iv) Some harmful non-biodegradable substances may caus diseases in living organisms.

Question. What are decomposers? What will be the consequence of their absence in an ecosystem?
Answer: Decomposers are the microbes that feed on dead and decay organisms. Dead plants and animals will get accumulated in the ecosystem as there would be no decomposers to decompose them. The decomposers will act upon dead and decayed organisms into simpler forms and get mixed in the soil which is used by producers again. But in the absence of decomposers this whole process would not occur and the dead organisms will get accumulated in the ecosystem.

Question. The following organisms form a food chain. Insects, hawk, grass, snake, frog. Arrange them in proper sequence to form a food chain? Which of these will have the highest concentration of non-biodegradable chemicals? Name the phenomenon associated with it?
Answer: Grass, insects, frog, snake, hawk.
Hawk will have the highest concentration of non-biodegradable chemicals as it is placed at the top level of the food chain. This phenomenon is called Biomagnification.

Question. What are trophic levels? Give an example of food chain and state the different trophic levels in it?
Answer: The distinct sequential steps or levels in the food chain where transfer of energy occurs are referred to as trophic levels.
Example of a food chain is:
Grass → Grasshopper → Lizard → Snake → Hawk
Grass is producer, it belongs to first trophic level. Grasshopper is
primary consumer, it belongs to second trophic level. Lizard is
secondary consumer, it belongs to third trophic level. Snake is
tertiary consumer and it belongs to fourth trophic level and hawk is
quaternary consumer, it belongs to fifth trophic level.