CBSE Class 12 Biology Ecosystem Question Bank

Class 12 Biology Study Guide: CBSE Class 12 Biology Ecosystem Question Bank

Review targeted academic resources with the CBSE Class 12 Biology Ecosystem Question Bank. Built according to official CBSE standards for the 2026-27 term, these downloadable Class 12 Biology study materials support effective daily practice and deeper conceptual understanding for Chapter 12 Ecosystem.

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CBSE Class 12 Biology Ecosystem Question Bank. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects. 

ECOSYSTEM
1. How is a food web formed? 
2. What is stratification in a forest?
3. Define standing crop? How is it measured?
4. What is the importance of humus? 
5. Why is secondary succession faster than primary succession?
6. Name the pioneers and climax of primary succession in water and on rocks. 
7. As succession proceeds the type and number of animals and decomposers also change.
8. Define ecological succession.What is sere 
9. What characteristic features are seen in Ecological succession? 
10. Why is there a restriction on trophic levels in a grazing food chain? Is there such a limitation in the detritus food chain? Explain. 
11. Schematically show the flow of energy in a grazing food chain from the sun. 
12. Justify the statement succession and evolution would have been parallel processes at that time when life started on earth. 
13. In general all pyramids are upright. Explain. What are the exceptions to this generalization? 
14. What are the limitations of ecological pyramids? 
15. What are the producers in grass land and oceans .How is GPP different from NPP? Why is the productivity in oceans lesser than on land?
16. Why is it reasonable to think that biodiversity should carry a hefty price tag? Justify. 
17. a, Why are Carbon and Phophorus essential to living organisms?
a. b, What are the natural reservoirs of these elements and in what form?
b. c, Give the important differences between the two cycles in nature ? 
18. With a flow chart explain the process of decomposition .What factors affect this process? work as a unit to perform the function? 
20. Humans do a disservice to nature by creating a desert from a forest. Comment and say why should it be a cause of concern?
 ECOSYSTEM
(QUESTION BANK)
ANSWER KEY
1 Interconnecting foodchains/one organism in different trophic levels 
2 The vertical levels of trees in a forest 
3 The mass of living matter at a given time measure of biomass ,dry weight of living matter at a given time
4 The colloidal matter resistant to microbial action ,reservoir of nutrients,breaks down slowly 
5 Soil already formed,spores,seeds remnants of vegetation
6 Phytoplanktons and forest,lichens and forest 
7 Vegetational changes, affect food and shelter for various types of animals 
8 Gradual fairly predictable change, in the species composition of a given area.The entire  sequence of communities that change in a given area during the succession
9 There is increase in diversity,species increase and increase in number,increase in biomass 
10 Energy decreases with successive levels. 10% only transferred to next level.
11 Sun----1%------- plants----2-10%-------herbivores------10%------carnivore 
12 Succession starts from the pioneer species giving way to seral communities before establishing the climax.Evolution also involves change of environmental factors followed by change in the communities containing fittest species
13 The producers are the most ,in terms of energy,biomass and number and subsequent levels are fewer in number,energy and Biomass .Energy decreases with successive
levels, The pyramid of Biomass in the oceans and pyramid of number in the case of a fruiting tree supporting hundreds of consumers ,the pyramids can be inverted.
14 Decomposers are not taken into account,two trophic levels may be taken up by the same species which is not considered,a food wb is not accomodated
15 Grass,phytoplanktons,GPP is the rate of Biomass production /g/yr whereas NPP is the rate of Biomass converted into plant matter and available for the consumers
(NPP=GPP-Respiration),Oceans have less solar energy available compared to land hence productivity is lower.
16 Ecosystem services include 1) maintaining soil 2) regulating rainfall 3) preventing erosion of soil,4) pollination 5)providing materials of medicinal,food and other values
17 Carbon part of all organic compounds ,Phosphorus for ATP,DNA etc Gaseous-Reservoir in atmosphere,Nitrogen cycle b)Sedimentary-Soil,eg-phosphorus. No gaseous component in phosphorus and reservoirs of the two are atmosphere and sediments respectively
18 Breakdown of complexorganicmatterbydecomposers.a)Process-i)fragmentation ii)leaching iii)catabolism.Humificationandmineralization–humificationleadsto accumulationofdarkcoloursubstancecalledhumus.Mineralisationresultinreleaseof inorgranic substances
a)climaticfactor– i)tempii)soilb)chemicalqualityofdetritus.Highertempandmoist condition – high rate of decomposition.Drysoil ,High temp–Lowrate
19 Productivity-producers,nutrient cycling and energy flow through the food chains-GFC & DFC,decomposition by the detritivores and decomposers
20 Ecosytem services include regulating the climate,hence livelihood and food of animals and people. Conversion of range land fedcropland, rainorirrigated cropland to desert like and,withadropinagriculturalproductivityof10%ormore.Itisusuallycausedbyacombination ofovergrazing,soilerosion,prolongeddrought,and climatechange. The soil becomes unsuitable for crops and vegetation food would also become scarce besides water and oxygen.
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Useful Resources and Notes for Class 12 Biology Chapter 12 Ecosystem

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Designed around the official curriculum, these study guides guarantee standard compliance. Reviewing step-by-step solutions clarifies complex sub-topics within Chapter 12 Ecosystem and demystifies standard marking schemes for Biology evaluations.

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Our advanced study package for Chapter 12 Ecosystem includes detailed concepts, diagrams, Mind Maps, and explanation of complex topics to ensure Class 12 students learn as per syllabus for 2026 exams.

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Does this material cover rationalized content for the 2026-27 CBSE session?

Yes, our subject matter experts have updated the Chapter 12 Ecosystem material to align with the rationalized NCERT textbooks and have removed deleted topics and added new competency-based questions.