Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

What is oogenesis? Give a brief account of oogenesis.

(i) Define translation.
(ii) Explain the translation process.
(iii) Draw a labelled diagram of the translation.

(a) Write the name of primates existing on earth about 15 million years ago. Write its important characteristics also?
(b) (i) From where did the animals similar to human being meet?
(ii) In which sequence were neanderthal, homohabilis and homo erectus evolved on earth?
(iii) When did modern man evolve on this planet?

Which of the following ecosystems will be more productive in terms of primary productivity? Justify your answer.
A young forest, a natural old forest, a shallow polluted lake, alpine meadow.

Trace the origin and evolution of Man.

1. Draw the embryo sac of a flowering plant and label:

1. Central cell
2. Chalazal end of the embryo sac
3. Synergids.

2. Name the cell that develops into the embryo sac and explain how this cell leads to the formation of embryo sac. Also mention the role played by the various cells of the embryo sac.

Give reasons why:
Most zygotes in angiosperms divide only after certain amount of endosperm is formed.

Unless the vector and source DNAs are cut, fragments separated and joined, the desired recombinant vector molecules cannot be created.

1. How are the desired DNA sequences cut?
2. Explain the technique used to separate the cut fragments.
3. How are the resultant fragments joined to the vector molecule?

About 8% of human male population suffers from colourblindness whereas only about 0.4% of human female population suffers from this disease. Write an explanation to show how it is possible.