© examsnet.com
Question : 2
Total: 7
(a) Define ecosystem.
(b) Autotrophs are at the first level of food chain. Give reason.
(c) In a food chain of frogs, grass, insects and snakes assign trophic level to frogs. To which category of consumers do they belong to ?
OR
(a) Explain the role of UV radiation in producing ozone layer.
(b) Mention the reaction involved.
(c) Why is excessive use of CFCs a cause of concern?
(b) Autotrophs are at the first level of food chain. Give reason.
(c) In a food chain of frogs, grass, insects and snakes assign trophic level to frogs. To which category of consumers do they belong to ?
OR
(a) Explain the role of UV radiation in producing ozone layer.
(b) Mention the reaction involved.
(c) Why is excessive use of CFCs a cause of concern?
Solution:
(a) An ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.
(b) The autotrophs or the producers are at the first trophic level because they prepare their own food by using the solar energy and in turn makes it available for hetero trophs or the consumers, since they depend on them for their food.
(c) In a grassland food chain, the initial organisms are grass. They are producers which produces food using solar energy. Insects are primary consumers. Who eat plants. They are called herbivores. Frogs are secondary consumers. Who eat insects. They are called carnivores. Snake are tertiary consumers. They are carnivores and eat frogs.
Thus, the correct answer is 'Grass > Insect > Frog > Snake.
The grass occupies the first trophic level which consists of producers. The second trophic level consist of primary consumers which is Insect and the Frog is assigned the Third trophic level of food chain consisting of secondary consumers.
OR
(a) Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen( O 2 ) ( O 2 ) ( O )
(b)
O 2
O . + O .
O . + O 2 → O 3
Ozone
(c) The use of the chemicals such as CFCs damages the ozone layer and leads to its depletion. At the higher levels of the atmosphere, ozone performs an essential function, it shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, since it is known to cause skin cancer in human beings.
(b) The autotrophs or the producers are at the first trophic level because they prepare their own food by using the solar energy and in turn makes it available for hetero trophs or the consumers, since they depend on them for their food.
(c) In a grassland food chain, the initial organisms are grass. They are producers which produces food using solar energy. Insects are primary consumers. Who eat plants. They are called herbivores. Frogs are secondary consumers. Who eat insects. They are called carnivores. Snake are tertiary consumers. They are carnivores and eat frogs.
Thus, the correct answer is 'Grass > Insect > Frog > Snake.
The grass occupies the first trophic level which consists of producers. The second trophic level consist of primary consumers which is Insect and the Frog is assigned the Third trophic level of food chain consisting of secondary consumers.
OR
(a) Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen
(b)
Ozone
(c) The use of the chemicals such as CFCs damages the ozone layer and leads to its depletion. At the higher levels of the atmosphere, ozone performs an essential function, it shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, since it is known to cause skin cancer in human beings.
© examsnet.com
Go to Question: