Human Reproduction — BIOLOGY STD 12 Science — Question

Ram saw a farmer spraying some chemicals on flowers. On asking farmer, he came to know that this act will lead to the formation of fruits without fertilisation. Ram thought that fruits developed in this way are not good to eat as chemicals are sprayed on it.
Next day, he asked his biology teacher about it, who explained him everything.

1. What chemicals were sprayed by the farmer?
2. Give difference between such a spray and usual pesticide spray?
3. What is parthenocarpy? Give its types.
4. What values are shown by Ram?

List the four important changes, taking place during biotic succession.

Ankit attended a blood donation camp to donate blood and came to know that he was HIV positive. He lost interest in studies knowing that. He remained absent from school for a long time. The biology teacher visited his house and talked to him. Ankit started coming to school again and showed interest in studies.

1. A person detected to be HIV positive should be isolated by the society. Do you agree? Why/ why not?
2. Write the processes through which, AIDS does not spread.
3. Who are at higher risk of encountering AIDS?
4. What sense of responsibility did the biology teacher exhibit?

Describe the structure of an antibody.

Describe the Polygonum type of embryo sac. Why is it referred to as monosporic?

Explain any three advantages the seeds offer to angiosperms.

Why should the spraying of DDT as an insecticide on vegetable crops be banned? Explain.

Explain the role(s) of the following in Biotechnology:

1. Restriction endonuclease.
2. Gel – electrophoresis.
3. Selectable markers in pBR322.

Suggest three features of plants that will prevent insect and pest infestation.

A sudden drop in active absorption of minerals is noticed if roots are deprived of oxygen supply.