List of top Biology Questions asked in CBSE CLASS XII

With the help of suitable diagram describe the logistic population growth curve.

Define the following terms and give one example for each:
(a) Commensalism
(b) Parasitism
(c) Camouflage
(d) Mutualism
(e) Interspecific competition

Define population and community.

Give an example for:
(a) An endothermic animal
(b) An ectothermic animal
(c) An organism of benthic zone

Define decomposition and describe the processes and products of decomposition.

Write a short note on
(a) Adaptations of desert plants and animals
(b) Adaptations of plants to water scarcity
(c) Behavioural adaptations in animals
(d) Importance of light to plants
(e) Effect of temperature or water scarcity and the adaptations of animals.

What is the ecological principle behind the biological control method of managing with pest insects?
An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?
Name important defence mechanisms in plants against herbivory.
If a population growing exponentially double in size in 3 years what is the intrinsic rate of increase (r) of the population?
Most living organisms cannot survive at temperature above 45°C°. How are some microbes able to live in habitats with temperatures exceeding 100°C?
Define phenotypic adaptation. Give one example.
If a marine fish is placed in a fresh water aquarium will the fish be able to survive? Why or why not?
How is diapause different from hibernation?
How do biofertilisers enrich the fertility of the soil?
Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd

Find out the role of microbes in the following and discuss it with your teacher.

(a) Single cell protein(SCP)
(b) Soil

Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.

Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?

Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.
Do you think microbes can also be used as source of energy? If yes,how?
What is sewage? In which way can sewage be harmful to us?
Name any two species of fungus which are used in the production of the antibiotics.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Name some traditional Indian foods made of wheat rice and bengal gram (or their products) which involve use of microbes.