Ecosystems — BIOLOGY STD 12 Science — Question

What are the characteristic symptoms of Down’s syndrome?

Name the two forms of reservoir of carbon that regulate the ecosystem carbon cycle.

To which product, following projects are related?

1. Blue revolution.
2. White revolution.
3. Green revolution.

Short Answer Questions
Describe three devices by which cross pollination is encouraged in Angiosperms by avoiding self-pollination?

Name the two heart sounds. How and when are they produced?

A teacher wants his/her students to find the genotype of pea plants bearing purple coloured flowers in their school garden. Name and explain the cross that will make it possible.

1. A DNA segment has a total of 2,000 nucleotides, out of which 520 are adenine containing nucleotides. How many purine bases this DNA segment possesses?
2. Draw a diagrammatic sketch of a portion of DNA segment to support your answer.

What is 'green revolution? Give any two examples each of the improved varieties of wheat and rice.

A doctor prescribed morphine as a sedative and pain killer to your cousin who had undergone surgery. Even after recovery, he craved for the prescribed medicine. What do you conclude about his condition, had he continued with the same medication? After appraising yourself, what measures will you suggest to him to overcome this problem? Briefly explain any two.

1. Why does DNA replication occur in small replication forks and not in its entire length?
2. Why is DNA replication continuous and discontinuous in a replication fork?
3. Explain the importance of origin of replication' in a replication fork.