Branching descent and natural selection are the two key concepts of Darwinian Theory of Evolution. Explain each concept with the help of a suitable example.

Scientists have succeeded in recovering healthy sugarcane plants from a diseased one.

1. Name the part of the plant used as explant by the scientists.

2. Describe the procedure the scientists followed to recover the healthy plants.

3. Name this technology used for crop improvement.

A. Name the enzyme that catalyses the transcription of hnRNA.

B. Why does the hnRNA need to undergo changes ? List the changes hnRNA undergoes and where in the cell such changes take place.

(i) Write the scientific names of the two species of filarial worms causing filariasis.

(ii) How do they affect the body of infected person(s)?

(iii) How does the disease spread?

Name the genus to which baculoviruses belong. Describe, their role in the integrated pest management programmes.

Unambiguous, universal and degenerate are some of the terms used for the genetic code. Explain the salient features of each one of them.

27.

Water is very essential for life. Write any three features both for plants and animals which enable them to survive in water scarce environment. 

How do organisms cope with stressful external environmental conditions which are localised or of short duration?

A. State the consequence if the electrostatic precipitator of a thermal plant fails to function.

B. Mention any four methods by which the vehicular air pollution can be controlled.

A. Draw a labelled diagram of L.S. of an embryo of grass (any six labels).

B, Give reason for each of the following:

(i) Anthers of angiosperm flowers are described as dithecous.
(ii) Hybrid seeds have to be produced year after year.