Reproductive Health — BIOLOGY STD 12 Science — Question

What is sewage? In which way can sewage be harmful to us ?

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?

Explain with the help of suitable examples the three different ways by which organisms overcome their stressful conditions lasting for short duration.

A person has to perform crosses for the purpose of studying inheritance of a few traits/ characters. What should be the criteria for selecting the organisms?

Write any four ways used to introduce a desired DNA segment into a bacterial cell in recombinant DNA technology experiments.

Define ecological succession. Give three differences between seral stages and climax community during succession.

Observe the diagram for genetic mapping of human DNA and answer the following questions:

i. Explain DNA polymorphism as the basis of genetic mapping of the human genome.
ii. State the role of VNTR in DNA fingerprinting.

What do you think is the significance of reproductive health in a society?

The graph given below shows species-area relationship of a certain region.

a. Study the graph and explain what it represents.
b. After a while, a small area was taken for constructing a road which divided the region into two. Write the impact this construction would have on species richness of the region.