Q24 of 43 Page 1

Describe the phosphorus cycle in an ecosystem.

• The natural reservoir of phosphorus is rock, which contains phosphorus in the form of phosphates.

• When rocks are weathered, minute amounts of these phosphates dissolve in soil solution and are absorbed by the roots of the plants.

• Herbivores and other animals obtain this element from plants.

• The waste products and the dead organisms are decomposed by phosphate-solubilising bacteria releasing phosphorus in soil.

How can childless couples be helped by the following assisted reproductive technologies:

→a) GIFT

→b) Cytoplasmic Sperm Injection

Compare the mechanism of evolution as put forth by Charles Darwin and de Vries.

Write by taking a suitable example, the convention followed for naming the restriction enzymes.

→a) Describe the experiment conducted by F. Griffith in 1928 with Streptococcus pneumoniae and write the conclusions he arrived at.

→b) State the contribution of Avery, MacLeod and McCarty in providing biochemical nature to the results as obtained by Griffith.

→a) Differentiate between convergent and divergent evolution by taking one suitable example of each.

→b) Explain adaptive radiation with the help of suitable examples.