Evolution — BIOLOGY STD 12 Science — Question

Correct the following statements:

1. Surgical methods of contraception prevent gamete formation.
2. All sexually transmitted diseases are completely curable.
3. Oral pills are very popular contraceptives among the rural women.
4. In E. T. techniques, embryos are always transferred into the uterus.

Explain in detail about pollen-pistil interaction.

How is PCR technique beneficial in biotechnology? How are the developed countries related to biopiracy cases? Explain with an example.

In the given diagram, write the names of parts shown with lines.

Name any six venereal diseases.

With an example explain lattitude gradient, as a pattern of biodiversity.

Prior a sports event blood and urine samples of sportspersons are collected for drug tests.

1. Why is there a need to conduct such tests?
2. Name the drugs the authorities usually look for.
3. Write the generic names of two plants from which these drugs are obtained.

What accounts for the greater ecological diversity of India?

In cattle, hornless (H) is dominant over horned (h) and black (B) is dominant over red (b). Consider that these two pairs of genes assort independently.

1. What proportion of the offspring from the cross, BbHh x bbhh, would be black and hornless?
2. From the cross Bbhh x Bbhh, how many will be:

1. Black and horned.
2. Red and horned.

1. Name the enzyme that catalyses the transcription of hnRNA.
2. Why does the hnRNA need to undergo changes? List the changes hn RNA undergoes and where in the cell such changes take place.