Biology

Ecosystem

Question:

Give any two examples of xerarch succession.

Answer:

(a) Bare rocks (xerosere)
(b) Sandy areas (psammosere)

previuos
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Ecosystem

Q 1.

Write important features of a sedimentary cycle in an ecosystem.

Q 2.

Given below is a figure of an ecosystem. Answer the following questions.
ncert-exemplar-problems-class-12-biology-ecosystem-2
(i) What type of ecosystem is shown in the figure?
(ii) Name any plant that is characteristic of such ecosystem.

Q 3.

Fill in the blanks.
(a)Plants are called as————- because  they fix carbon dioxide.
(b)In an ecosystem dominated by trees, the  pyramid (of numbers) is————- type.
(c)In aquatic ecosystems, the limiting factor  for the productivity is————- .
(d)Common detritivores in our ecosystem  are————- .
(e)The major reservoir of carbon on earth  is————- .

Q 4.

What is primary productivity? Give brief description of factors that affect primary productivity.

Q 5.

What is the ultimate source of energy for the ecosystems?

Q 6.

Name any two organisms which can occupy more than one trophic level in an ecosystem.

Q 7.

Among bryophytes, lichens and fern which one is a pioneer species in a xeric succession?

Q 8.

Why is the rate of assimilation of energy at the herbivore level called secondary productivity?

Q 9.

Human activities interfere with carbon cycle. List any two such activities.

Q 10.

Arrange the following as observed in vertical stratification of a forest: Grass, Shrubby plants, Teak, Amaranths

Q 11.

Why are nutrient cycles in nature called biogeochemical cycles?

Q 12.

Primary productivity varies from ecosystem to ecosystem. Explain.

Q 13.

What is common to earthworm, mushroom, soil mites and dung beetle in an ecosystem.

Q 14.

A farmer harvests his crop and expresses his harvest in three different ways.
(a) I have harvested 10 quintals of wheat.
(b) I have harvested 10 quintals of wheat today in one acre of land.
(c) I have harvested 10 quintals of wheat in one acre of land, 6 months after sowing.
Do the above statements mean one and the same thing. If your answer is yes, give reasons. And if your answer is ‘no' explain the meaning of each expression.

Q 15.

The number of trophic levels in an ecosystem are limited. Comment.

Q 16.

Is the common edible mushroom an autotroph or a heterotroph?

Q 17.

What are the shortcomings of ecological pyramids in the study of ecosystem?

Q 18.

A part from plants and animals, microbes form a permanent biotic component in an ecosystem. While plants have been referred to as autotrophs and animals as heterotrophs, what are microbes referred to as? How do the microbes fulfil their energy requirements?

Q 19.

What will happen to an ecosystem if:
(a) All producers are removed;
(b) All organisms of herbivore level are eliminated; and
(c) All top carnivore population is removed

Q 20.

Name an organism found as secondary carnivore in an aquatic ecosystem.

Q 21.

In relation to energy transfer in ecosystem, explain the statement "10 kg of deer's meat is equivalent to 1 kg of lion's flesh".

Q 22.

Define self sustainability.

Q 23.

Give any two examples of xerarch succession.

Q 24.

Flow of energy through various trophic levels in an ecosystem is unidirectional and non-cyclic. Explain.

Q 25.

Give an account of energy flow in an ecosystem.

Q 26.

What is an incomplete ecosystem? Explain with the help of suitable example.

Q 27.

What does the base tier of the ecological pyramid represent?

Q 28.

In the North East region of India, during the process of Jhum cultivation, forests are cleared by burning and left for regrowth after a year of cultivation. How would you explain the regrowth of forest in ecological term?

Q 29.

What could be the reason for the faster rate of decomposition in the tropics?

Q 30.

Why are oceans least productive?

Q 31.

Fill in the trophic levels (1, 2, 3 and 4) in the boxes provided in the figure.
ncert-exemplar-problems-class-12-biology-ecosystem-3

Q 32.

Which of the following ecosystems will be more productive in terms of primary productivity? Justify your answer. A young forest, a natural old forest, a shallow polluted lake, alpine meadow.

Q 33.

Define decomposition and describe the processes and products of decomposition.

Q 34.

Justify the following statement in terms of ecosystem dynamics. "Nature tends to increase the gross primary productivity, while man tends to increase the net primary productivity".

Q 35.

Organisms at a higher trophic level have less energy available. Comment.

Q 36.

Poaching of tiger is a burning issue in today's world. What implication would this activity have on the functioning of the ecosystem of which the tigers are an integral part?

Q 37.

Is an aquarium a complete ecosystem?

Q 38.

Climax stage is achieved quickly in secondary succession as compared to primary succession. Why?

Q 39.

Give an account of energy flow in an ecosystem.

Q 40.

Describe the components of an ecosystem.

Q 41.

Sometimes due to biotic/abiotic factor the climax remain in a particular serai stage (pre climax) without reaching climax. Do you agree with this statement? If yes, give a suitable example.

Q 42.

Name an omnivore which occurs in both grazing food chain and the decomposer food chain.

Q 43.

What is a biogeochemical cycle? What is the role of the reservoir in a biogeochemical cycle? Give an example of a sedimentary cycle with reservoir located in earth's crust.

Q 44.

Distinguish between
(a)Grazing food chain and detritus food chain
(b)Production and decomposition
(c)’Upright and inverted pyramid
(d)Food chain and food web
(e)Litter and detritus
(f)Primary and secondary productivity

Q 45.

The biodiversity increases when one moves from the pioneer to the climax stage. What could be the explanation?

Q 46.

Under what conditions would a particular stage in the process of succession revert back to an earlier stage?

Q 47.

Justify the pitcher plant as a producer.

Q 48.

Given below is a list of autotrophs and heterotrophs. With your knowledge about food chain, establish various linkages between the organisms on the principle of ‘eating and being eaten'. What is this inter-linkage established known as?
Algae, Hydrilla, grasshopper, rat, squirrel, crow, maize plant, deer, rabbit, lizard, wolf, snake, peacock, phytoplankton, crustaceans, whale, tiger, lion, sparrow, duck, crane, cockroach, spider, toad, fish, leopard, elephant, goat, Nymphaea, Spirogyra.

Q 49.

Define’ecological pyramids and describe with examples, pyramids of number and biomass.

Q 50.

The rate of decomposition of detritus is affected by the abiotic factors like availability of oxygen, pH of the soil substratum, temperature etc. Discuss.