Respiration and Circulation — BIOLOGY STD 12 Science — Question

1. Why did Hershey and Chase use radioactive sulphur and radioactive phosphorus in their experiment?
2. Write the conclusion they arrived at and how.

What percent of all bird species and mammal species, respectively face the threat of extinction?

The establishment of genomic library is more meaningful in prokaryotes than in eukaryotes.

Draw the next mature stage and label the parts.

The species diversity of plants (22 per cent) is much less than that of animals (72 per cent). What could be the explanations to how animals achieved greater diversification?

Give the applications of PCR technique.

Explain the cause of chromosomal disorders in humans. Describe the effect of such disorders with the help of an example each involving.

1. autosomes, and
2. sex chromosomes.

Ornithologists observed a decline in the bird population in the area near a lake after the setting of an industrial unit in the same area. Explain the cause responsible for the decline observed

A non–haemophilic couple was informed by their doctor that there is possibility of a haemophilic child be born to them. Explain the basis on which the doctor conveyed this information. Give the genotypes and the phenotypes of all the possible children who could be born to them.

Describe physiological effect and applications of gaseous hormone in plants.