NCERT Exemplar - Ecosystem (Part - 1 ) Notes | EduRev

Biology Class 12

Created by: Sushil Kumar

NEET : NCERT Exemplar - Ecosystem (Part - 1 ) Notes | EduRev

The document NCERT Exemplar - Ecosystem (Part - 1 ) Notes | EduRev is a part of the NEET Course Biology Class 12.
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MULTIPLE CHOICE QUESTIONS 

Q.1. Decomposers like fungi and bacteria are:
(i) Autotrophs
(ii) Heterotrophs
(iii) Saprotrophs

(iv) Chemo-autotrophs.
Choose the correct answer:
(a) i and iii,
(b) i and iv
(c) ii and iii,
(d) i and ii
Ans.
(c)
Solution.
Decomposers like fungi and bacteria are heterotrophs and saprotrophs.

Q.2. The process of mineralisation by micro organisms helps in the release of:
(a) Inorganic nutrients from humus
(b) Both organic and inorganic nutrients from detritus
(c) Organic nutrients from humus
(d) Inorganic nutrients from detritus and formation of humus.
Ans. 
(a)

  • The process of mineralisation by microorganisms helps in the release of inorganic nutrients from humus.
  • The humus is further degraded by some microbes and release of inorganic nutrients occur by the process called mineralisation.


Q.3. Productivity is the rate of production of biomass expressed in terms of:
(i) (kcal m-3) yr-1 
(ii) g-2 yr-1 
(iii) g-1 yr-1 
(iv) (kcal m-2) yr-1 
(a) ii,
(b) iii,
(c) ii and iv,
(d) i and iii
Ans.
(c)
Solution.
Productivity is the rate of production of biomass expressed in terms of g-1yr-1 and (heal m-2) yr-1.

Q.4. An inverted pyramid of biomass can be found in which ecosystem?
(a) Forest
(b) Marine
(c) Grass land
(d) Tundra
Ans. 
(b)
Solution.
In terrestrial ecosystem pyramid of biomass is generally upright. The pyramid of biomass in sea or lake is generally inverted because the biomass of fishes for exceeds that of phytoplankton.

Q.5. Which of the following is not a producer?
(a) Spirogyra
(b) Agaricus
(c) Volvox
(d) Nostoc
Ans. 
(b)
Solution.
Spirogyra, Volvox and Nostoc are producers. Agaricus is a fungus.

Q.6. Which of the following ecosystems is most productive in terms of net primary production?
(a) Deserts
(b) Tropical rain forests
(c) Oceans
(d) Estuaries
Ans.
(b)
Solution.
Tropical rain forests ecosystems is most productive in terms of net primary production.

Q.7. Pyramid of numbers is:
(a) Always upright
(b) Always inverted
(c) Ether upright or inverted
(d) Neither upright nor inverted
Ans.
(c)
Solution.
Pyramid of number in grassland or forest or pond ecosystem is upright. In parasitic food chain, the pyramid of number is inverted. In an ecosystem dominated by trees, the pyramid of number is spindle shaped/inverted.

Q.8. Approximately how much of the solar energy that falls on the leaves of a plant is converted to chemical energy by photosynthesis?
(a) Less than 1%
(b) 2-10%
(c) 30%
(d) 50%
Ans.
(b)
Solution.
Approximately how much of the solar energy that falls on the leaves of a plant is converted to chemical energy by photosynthesis 2-10%.

Q.9. Among the following, where do you think the process of decomposition would be the fastest?
(a) Tropical rain forest
(b) Antarctic
(c) Dry arid region
(d) Alpine region
Ans. 
(a)
Solution.

  • Warm and moist environment favour decomposition. Decomposition is largely an oxygen requiring process. Low temperature and anaerobiosis inhibit decomposition resulting in build up of organic materials.
  • The process of decomposition would be the fastest is tropical rain forest.


Q.10. How much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores?
(a) 1%
(b) 10%
(c) 40%
(d) 90%
Ans.
(b)
Solution.
10% of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores.

Q.11. During the process of ecological succession the changes that take place in communities are:
(a) Orderly and sequential
(b) Random
(c) Very quick
(d) Not influenced by the physical environment
Ans.
(a)
Solution.
The gradual and fairly predictable change in the species composition of a given area is called ecological succession. An important characteristic of all the communities is that their composition and structure constantly change in response to the changing environmental conditions. These changes are orderly and sequential parallel with the changes in the physical environment.

Q.12. Climax community is in a state of:
(a)
Non-equilibrium
(b) Equilibrium
(c) Disorder
(d) Constant change.
Ans. (b)

Q.13. Among the following bio-geo-chemical cycles which one does not have losses due to respiration?
(a) Phosphorus
(b) Nitrogen
(c) Sulphur
(d) All of the above
Ans.
(d)
Solution.
Phosphorus, nitrogen and sulphur bio-geo-chemical cycles does not have losses due to respiration.

Q.14. The sequence of communities of primary succession in water is:
(a) Phytoplankton, sedges, free-floating hydrophytes, rooted hydrophytes, grasses and trees.
(b) Phytoplankton, free-floating hydrophytes, rooted hydrophytes, sedges, grasses and trees.
(c) Free-floating hydrophytes, sedges, phytoplankton, rooted hydrophytes, grasses and trees.
(d) Phytoplankton, rooted submerged hydrophytes, floating hydrophytes, reed swamp, sedges, meadow and trees.
Ans.
(b)
Solution.
The sequence of communities of primary succession in water is phytoplankton, free-floating hydrophytes, rooted hydrophytes, sedges, grasses and trees.

Q.15. The reservoir for the gaseous type of bio-geo chemical cycle exists in
(a)
Stratosphere
(b) Atmosphere
(c) Ionosphere
(d) Lithosphere
Ans. (b)

Q.16. If the carbon atoms fixed by producers already have passed through three species, the trophic level of the last species would be.
(a)
 Scavenger
(b) Tertiary producer
(c) Tertiary consumer
(d) Secondary consumer

Ans. (c)
Solution.
If the carbon atoms fixed by producer already have passed through three species then the trophic level of the last species (i.e., third species) would be tertiary consumer.

Q.17. Which of the following type of ecosystem is expected in an area where evaporation exceeds precipitation, and mean annual rainfall is below 100 mm
(a) Grassland
(b) Shrubby forest
(c) Desert
(d) Mangrove

Ans. (c)
Solution.
Desert ecosystem is expected in an area where evaporation exceeds precipitation, and mean annual rainfall is below 100 mm.

Q.18. The zone at the edge of a lake or ocean which is alternatively exposed to air and immersed in water is called:
(a)
Pelagic zone
(b) Benthic zone
(c) Lentic one
(d) Littoral zone
Ans. (d)

Q.19. Edaphic factor refers to:
(a)
Water
(b) Soil
(c) Relative humidity
(d) Altitude
Ans. (b)

Q.20. Which of the following is an ecosystem service provided by a natural ecosystem?
(a) Cycling of nutrients
(b) Prevention of soil erosion
(c) Pollutant absorption and reduction of the threat of global warming
(d) All of the above
Ans.
(d)
Solution.
Cycling of nutrients, prevention of soil erosion and pollutant absorption and reduction of the threat of global warming is an ecosystem service provided by a natural ecosystem.


VERY SHORT ANSWER TYPE QUESTIONS 

Q.1. Name an organism found as secondary carnivore in an aquatic ecosystem.
Ans. 
Catfish/water snake etc.

Q.2. What does the base tier of the ecological pyramid represent?
Ans.
Producers

Q.3. Under what conditions would a particular stage in the process of succession revert back to an earlier stage?
Ans.
Natural or human induced disturbances like fire, deforestation etc.

Q.4. Arrange the following as observed in vertical stratification of a forest: Grass, Shrubby plants, Teak, Amaranths.
Ans.
Grass, Amaranths, Shrubby plants, Teak

Q.5. Name an omnivore which occurs in both grazing food chain and the decomposer food chain.
Ans.
Sparrow/crow

Q.6. Justify the pitcher plant as a producer.
Ans. 
It is chlorophyllous and is thus capable of photosynthesis.

Q.7. Name any two organisms which can occupy more than one trophic level in an ecosystem.
Ans.
Man and sparrow etc.

Q.8. 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?
Ans.
The regrowth of forest is called secondary succession.

Q.9. Climax stage is achieved quickly in secondary succession as compared to primary succession. Why?
Ans.
The rate of succession is much faster in secondary succession as the substratum (soil) is already present as compared to primary succession where the process starts from a bare area (rock).

Q.10. Among bryophytes, lichens and fern which one is a pioneer species in a xeric succession?
Ans.
Crustose lichens.

Q.11. What is the ultimate source of energy for the ecosystems?
Ans.
Sunlight (solar radiation)

Q.12. Is the common edible mushroom an autotroph or a heterotroph?
Ans.
Heterotroph (as it does not have chlorophyll)

Q.13. Why are oceans least productive?
Ans.
Oceans are least productive because they do not receive sufficient sunlight which is necessary for 1° productivity.

Q.14. Why is the rate of assimilation of energy at the herbivore level called secondary productivity?
Ans.
It is because the biomass available to the consumer for consumption is a resultant of the primary productivity from plants.

Q.15. Why are nutrient cycles in nature called biogeochemical cycles?
Ans.
Nutrient cycles in nature called biogeochemical cycles because the cycling of nutrients occurs between living organisms (bio) and non-living things-geo- (rocks, air and water, etc.)

Q.16. Give any two examples of xerarch succession.
Ans.
 
(a) Bare rocks (xerosere)
(b) Sandy areas (psammosere)

Q.17. Define self sustainability.
Ans.
The degree at which the system can sustain itself without external support is called self sustainability.

Q.18. Given below is a figure of an ecosystem. Answer the following questions.

NCERT Exemplar - Ecosystem (Part - 1 ) Notes | EduRev

(i) What type of ecosystem is shown in the figure.
(ii) Name any plant that is characteristic of such ecosystem.
Ans.
 
(i) Desert ecosystem
(ii) Opuntia, Cacti and Acacia

Q.19. What is common to earthworm, mushroom, soil mites and dung beetle in an ecosystem.
Ans.
They are all detritivores i.e., decomposing organisms which feed on dead remains of plants and animals.

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