Ecosystem: Class 12 Previous Year Questions

Ecosystem questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. _________ Page 19 of 24 { } 30. Below is shown a pond that represents a self-sustaining natural ecosystem with both biotic and abiotic components interacting in a balanced food web. Based on the diagram, answer the questions : (a) Mention two abiotic component…
   Board 20264 marksshort answer
2. _________ Page 13 of 24 { } 21. (a) Given below is a pyramid found in an ecosystem, where each bar represents the standing crop available in the trophic level. (i) Identify the kind of pyramid and with the help of an example explain the conditions where this k…
   Board 20262 marksshort answer
3. Assertion (A) : In terrestrial ecosystem much larger fraction of energy flows through grazing food chain. Reason (R) : Grazing food chain may be connected to Detritus food chain at some levels.
   Board 20261 markAssertion-Reason
4. Student to attempt either option-(A) or (B) : (A) Analyse the following ecosystems and discuss, which will be more productive in terms of primary productivity : A young forest, a natural old forest, a shallow polluted lake. OR (B) Differentiate between Net pri…
   Board 20252 marksshort answer
5. Student to attempt either option (A) or (B). (A) Identify the type of pyramid given below and write two identifying features of such a pyramid : OR (B) (i) Construct an ideal pyramid of energy when 10,00,000 Joules of sunlight is available. (i) Mention the ene…
   Board 20252 marksshort answer
6. Study the diagram of a pyramid of biomass given below. Name the two Name this type of pyramid and the ecosystem in which it is found.
   Board 20242 marksshort answer
7. The rate of formation of new organic matter by consumers, and the biomass available for consumption of herbivores as well as decomposers are referred to as : (A) Gross primary productivity and Net primary productivity (B) Net primary productivity and Secondary…
   Board 20241 markMCQ
8. Assertion (A) : Indian Government has set up an organisation known as GEAC to decide the validity of GM research. Reason (R) : Genetic modification of organisms has no effect when such organisms are introduced in the ecosystem. 10 IÊS> I 17. ZrMo Xr JB© Vm{bH$…
   Board 20241 markAssertion-Reason
9. JJJJ Page 16 22. Ho$db `moOZmË_H$ AmaoI H$s ghm`Vm go, BH$mo Ama dZ (EcoRI) Am¡a S>rEZE bmBJoµO à{V~§YZ H$s {H«$`m Ûmam nwZ`m}JO S>rEZE Ho$ {Z_m©U Ho$ VrZ MaUm| H$mo Xem©BE & 3 19. (a) (i) image given below : (ii) State their importance in various biotechnolog…
   Board 20233 marksshort answer
10. Given below is a food web that involves nine organisms. (a) Identify two producers and two carnivores shown in the food web. (b) Is it possible to make an ecological pyramid depicting this food web ? Give reason in support of your answer.
    Board 20232 marksshort answer
11. Which of the following is possible in an aquatic ecosystem? Pyramid of numbers Pyramid of biomass Pyramid of energy a) Inverted Upright Inverted b) Upright Upright Upright c) Inverted Inverted Inverted d) Upright Inverted Upright.
    CBSE practice 2023-241 markAssertion-Reason
12. Rupal says that in marine food chains where the pyramid of biomass is inverted, the 10% rule of energy transfer is not applicable. Is she CORRECT and why? (a) No, because every level still gets 10% of the energy from the lower level. (b) Yes, because there are…
    CBSE practice 2023-241 markAssertion-Reason
13. Biomass is expressed in terms of dry weight and / or fresh weight. Which of the weights is more accurate as a unit of standing crop? Justify your answer with a reason. OR Marshy areas often consist of hard outer coverings as detritus that are remains of organi…
    CBSE practice 2022-232 marksshort answer
14. Shown below is a food chain. (a) Millipedes have a hard exoskeleton whose composition is different from that of the leaves. Considering all other conditions to remain the same, which step is likely to be slower between A to B and B to C and why? (b) What would…
    CBSE practice 2023-242 marksshort answer
15. Explain how the ecosystem follows the first and the second law of thermodynamics. OR a) Study the ecological pyramid of numbers given below and suggest some situations in which it is applicable. b) Give two reasons why the percentage of energy transferred to c…
    CBSE practice 2023-242 marksshort answer
16. Attempt either option A or B. A. The table below is a hypothetical data on Seasonal Temperatures seen over two different zones Region Temp. in Spring (oC) Temp. in Summer (oC) Temp. in Autum n (oC) Temp. in Winter (oC) Primary Productivity (GPP) (g/m2/ year) R…
    Sample paper 2026-272 marksshort answer
17. Which of the following is most likely to be true about the percentage of energy received by a horse and a crow from the producers in different food chains? Horse Crow P always the same always the same Q always the same can be different R can be different alway…
    CBSE practice 2022-231 markMCQ

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