Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Biology

Write the scientific name of the source organism of the thermostable DNA polymerase used in PCR.

State the advantage of using Thermostable DNA polymerase.

"Biodiversity plays a major role in many ecosystem services that nature provides."

Describe any two broadly utilitarian arguments to justify the given statement.

"Biodiversity plays a major role in many ecosystem services that nature provides."

State one ethical reason for conserving biodiversity.

Bioreactors are the containment vehicles of any biotechnology-based production process. For large scale production and for economic reasons the final success of biotechnological process depends on the efficiency of the bioreactor.

Answer the following questions w.r.t. the given paragraph:

1. List the operational guidelines that must be adhered to so as to achieve optimisation of the bioreactor system. Enlist any four.
2. Mention the phase of the growth we refer to in the statement "Optimisation of growth and metabolic activity of the cells".
3. Is the biological product formed in the bioreactor suitable for the intended use immediate? Give reason in support of your answer.

Interaction between clown fish living among the stinging tentacles of sea anemone is an example of ______.

"Abingdon tortoise in Galapagos islands became extinct within a decade on introduction of goats in the island." Explain giving reason.

Many copepods live on the body surface of marine fish. This relationship is an example of ______.

"Some species of insects and frogs have evolved with various specific features that help them from being detected."

1. Justify the statement giving reasons.
2. Mention any two such features.

A pregnant human female was advised to undergo MTP. It was diagnosed that the fetus she was carrying had developed from a zygote having 45 chromosomes with only one X chromosome.

1. What is this condition called and how does it arise?
2. Why was she advised to undergo MTP?

A farmer grew 2 varieties of corn crops in fields A and B. He grew normal corn crops in field A and GM corn crops in field B. He observed corn borers attacked only in field A. To control it, spores of Bt were sprayed in field A.

1. Name the gene in the spores responsible for the control of this pest.
2. What effect will the spores of Bt have on the insect pest?
3. How has field B developed resistance against this pest?

Observe the graph given below.

a) Which species is competitively superior? Support it with the data provided in the graph.

b) State the underlying principle for the above result and name the scientist associated with this principle.

c) Explain the mechanism in which two or more species competing with each other can co-exist.

OR

Graphs A and B shown below depict interaction of two species. Which graph indicates Mutualism? Give reason.

A	B

Give one example of commensalism.

Give one example of parasitism.

Give one example of camouflage.

What is the role of sacred groves in conservation?

“It is often said that the pyramid of energy is always upright. On the other hand, the pyramid of biomass can be both upright and inverted.” Explain with the help if examples and sketches.

Name the group of genes that have been identified in normal cells that could lead to cancer. How do these genes cause cancer?

Why the pyramid of energy is always upright? Explain.

Indiscrimate diagnostic practices using X-rays etc., should be avoided. Give one reason.