Organisms & Populations: Class 12 Previous Year Questions

Organisms & Populations 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 17 of 24 { } 29. The diagram below shows the distribution of two barnacle species, Chthamalus and Balanus on a rocky sea shore. When Balanus is experimentally removed, Chthamalus expands its range in lower intertidal zone. _________ Page 18 of 2…
   Board 20264 marksshort answer
2. _________ Page 5 of 24 { } 6. In an ecosystem, different species occupy different levels and vertical distribution of species is found. This is called _________. 1 (A) Stratification (B) Layering (C) Fragmentation (D) Population _________ Page 6 of 24 { } 7. …
   Board 20261 markMCQ
3. Assertion (A) : The population of melanized moths increased in industrial areas after Industrial Revolution. Reason (R) : In Industrial environment lichen covered trees were replaced by soot-covered trees offering better camouflage to dark coloured moths.
   Board 20261 markAssertion-Reason
4. What could be the reason of extinction of Abingdon Tortoise from Galapagos Islands ? 1 (A) Intraspecific Competition (B) Predation (C) Parasitism (D) Interspecific Competition
   Board 20261 markMCQ
5. Read the following passage and answer the questions that follow : majority of them live in groups in a well-defined geographical area, share or compete for similar resources, potentially interbreed and thus constitute a population. The population has certain a…
   Board 20254 markscase-based
6. (a) Draw a graph for a population whose population density has reached the carrying capacity. (b) Out of the two population growth curves, which one is considered a more realistic for most populations ? Why ? (c) Draw a growth curve where resources are not lim…
   Board 20253 marksshort answer
7. A population is in genetic equilibrium/Hardy-Weinberg equilibrium for a f the 0·6, then the frequency of genotype Aa is : (A) 0·21 (B) 0·42 (C) 0·48 (D) 0·32
   Board 20241 markMCQ
8. Predation is referred to as a detrimental interaction. Explain any three positive roles, supported by an example each, that a predator plays in an ecosystem.
   Board 20243 marksshort answer
9. JJJJ Page 23 28. Explain the following population interactions with the help of one example each : 3 (a) Brood Parasitism (b) Co-evolution of mutualists JJJJ Page 24 IÊS> K 29. MmQ>© Ûmam Xem©`m J`m h¡ & MmQ>© H$m AÜ``Z H$s{OE VWm CgHo$ ZrMo {XE JE àíZm| Ho$ C…
   Board 20233 marksshort answer
10. Human settlement often leads to habitat loss which leads to fragmentation, forming smaller patches of habitats. Select the statements that describe how a small patch differs from a large patch of the same habitat. (i) Invasive species will never be seen here. …
    Board 20231 markMCQ
11. Identify the option that does not exhibit a parasitic relationship. (a) Head lice in humans (b) Cuscuta on a mango tree (c) Female Anopheles (d) Ticks on dogs
    Board 20231 markMCQ
12. What is the importance of female Anopheles mosquitoes in the life of a malarial Parasite Plasmodium ? "A' Ph lnhlh le /· I, () 6. 1200- 1000- 800 ·2)600 - 5h 400 200 1993 1994 1996 1997 1998 1999 2000 2002 1992 1995 2001 2003 : Fijisharkdiving.blogspot.com a h…
    Board 20221 markvery short
13. Study the graph given below, showing the population growth curves ·A' and ·B' respectively. Answer the following questions : Carrying Capacity Population size Time/ Generation· (a) What is ·Carrying Capacity' in respect of Curve ·B' indicative of ? (b) Mention…
    Board 20221 markvery short
14. (a) Study the given graphs (X) and (Y) depicting the annual variation in solar radiation on Earth from January to December and answer the undermentioned questions. (i) Identify the graph that depicts (I) tropical region, and (II) temperate region, respectively…
    Board 20221 markvery short
15. In a population of 1000 individuals, 25% of individuals show the phenotype for sickle cell anaemia (genotype - ss). (a) Assuming the population meets Hardy-Weinberg equilibrium, how many individuals would be carriers of the sickle cell allele but will not show…
    CBSE practice 2022-233 marksshort answer
16. In a huge culture flask with unlimited supply of nutrient medium, bacteria were grown. Their population kept on increasing as they were dividing by binary fission. a) What type of growth pattern will be seen in this population? b) Write the equation which can …
    CBSE practice 2023-244 marksshort answer
17. Populations of organisms respond differently to the abiotic factors of the environment. Organisms that are able to maintain physiological homeostasis ensuring constant body temperature are called regulators while others that cannot, are termed as conformers. C…
    CBSE practice 2021-223 marksshort answer
18. State whether each of these statements given below is/are true or false. Justify your answer. (a) Flocs reduce the pollution in water by increasing its BOD. (b) Mycorrhiza is a type of parasitic relationship in which only the plants benefit from fungi.
    CBSE practice 2023-243 marksshort answer
19. The nematode Myrmeconema neotropicum lives inside the abdomen of certain tropical ants (Cephalotes atratus). Inside the ant’s body, the nematode develops slowly without killing it. Once mature, it changes the color of the ant’s abdomen to bright red, making it…
    Sample paper 2026-273 marksshort answer
20. The population growth can be exponential (unimpeded) or logistic (competitive). These growth curves can be represented by the graphs as shown below: (a) Define carrying capacity. (b) What limits the growth of organisms as seen in the graphs above? [2 marks]
    CBSE practice 2021-222 marksshort answer

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