Aasan
ORGANISMS AND DISEASE
Class 12 - Biology
Time Allowed: 1 hour Maximum Marks: 40
Section A
1. In asymptote state, population is: [1]
a) Increasing b) Changing
c) Stabilized d) Decreasing
2. Which should be considered a more realistic growth model? [1]
a) Allen's model b) Exponential growth
c) Verhulst-Pearl logistic growth d) Geometric growth
3. Which of the following is correctly matched? [1]
a. Stratification- Population
b. Aerenchyma - Opuntia
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c. Age pyramid - Biome
d. Parthenium hysterophorus - Threat to biodiversity
a) Age pyramid - Biome b) Stratification - Population
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c) Aerenchyma - Opuntia d) Parthenium hysterophorus - Threat to
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biodiversity
4. An interaction favourable to both the populations, but not obligatory to either is: [1]
a) Commensalism b) Mutualism
c) Proto-cooperation d) Parasitism
5. An example of predation is [1]
a) Dog gives birth twice in a year b) Cuckoo laying eggs in crow’s nest
c) Biological control of pest population d) Penicillium whose toxins kill bacteria
6. A cuckoo laying eggs in the nest of other species of birds, is an example of: [1]
a) Hyperparasitism b) Brood parasitism
c) Ectoparasitism d) Adephoparasitism
7. A sedentary sea anemone gets attached to the shell lining of hermit crab. The association is : [1]
a) Symbiosis b) Ectoparasitism
c) Commensalism d) Amensalism
8. A population has more young individuals compared to the older individuals. What would be the status of the [1]
population after some years?
a) It will stabilise b) It will increase
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c) It will first decline and then stabilise d) It will decline
9. Assertion (A): Cuscuta is an example of holoparasite. [1]
Reason (R): Cuscuta does not depend on other plants for nutrition requirements.
a) Both A and R are true and R is the correct b) Both A and R are true but R is not the
explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.
10. Assertion (A): Predators also help in maintaining species diversity in a community, by reducing the intensity of [1]
competition among competing prey species.
Reason (R): When all the starfish (Pisaster) were removed from an enclosed intertidal area, of the American
Pacific Coast more than 10 species of invertebrates became extinct within a year, because of interspecific
competition.
a) Both A and R are true and R is the correct b) Both A and R are true but R is not the
explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.
11. Assertion (A): Mycorrhizal relation exists between Boletus and Pinus. [1]
Reason (R): It is a symbiotic interaction. AN
a) Both A and R are true and R is the correct b) Both A and R are true but R is not the
explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.
Section B
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12. Give two examples of mutualism in living organisms. [2]
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13. a. Explain how it is ensured that the orchid Ophrys is pollinated by a specific species of bee. [2]
b. Describe co-evolution with the help of this example.
14. The population of a metro city experiences fluctuations in its population density over a period of time. [2]
a. When does the population in a metro city tend to increase?
b. When does the population in metro city tend to decline?
c. If N is the population density at the time t, write the population
density at the time t + 1.
Section C
15. Study the table showing the population interaction between species Z and Y respectively. Assign the appropriate [3]
+/– signs for A, B, D, E and respective interactions for C and F.
Species 'Z' Species 'Y' Name of Interaction
A B Mutualism
– – C
D E Parasitism
+ O F
16. Differentiate between the following inter-specific interactions in a population - [3]
(i) Mutualism and completion.
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(ii) Commensalisms and Amensalism.
17. Discuss the various types of positive interactions between species. [3]
Section D
18. Study the figures given below that depict the comparative age distribution of human populations in Sweden and [4]
Rwanda. (International Data Base 2003) and answer the questions that follow:
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a. What can be inferred from the very broad base of Rwanda's age pyramid? Support your answer with the data
provided in the figure. (2)
b. Sweden has an age distribution that is approximately of the same width near its base as at the apex. What
does this indicate? (1)
c. Name the type of age pyramid shown above for Sweden. (1)
OR
Name the type of age pyramid shown above for Rwanda. (1)
Section E
19. Differentiate between the following: [5]
i. Intraspecific and Interspecific competition
ii. Mutualism and Commensalism
iii. Immigration and Emigration.
20. With the help of suitable diagram describe the logistic population growth curve. [5]
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