Evolution — BIOLOGY STD 12 Science — Question

What are recombinant DNA vaccines? Give two examples of such vaccines. Discuss their advantages.

Naman entered into a quarrel with some farmers who were spraying DDT in their field. Many people gathered at the spot to see and enjoy the incident. The angry mob demanded that Naman should not interfere in the farmer's job. Naman tried to explain his point and finally succeeded in explaining the harmful effects of DDT.

1. What is biomagnification? Explain with an example.
2. Is biomagnification related with DDT only? Comment.
3. What is the effect of DDT on birds?
4. What values did Naman promote?

Life cycle of Plasmodium.

Directional, Stabilizing and Disruptive selection.

Study the table given below and answer the questions that follow:

Species A	Species B	Name of interaction
(+)	(+)	(A)
(-)	(-)	(b)
(+)	(-)	(c)
(+)	(0)	(d)

+ = Beneficial interaction
- = Detrimental interaction
0 = Neutral interaction
Identify a, b, c and d in the given table and explain any three of them with the help of an example each.

Using Punnett square demonstrate the law of independent assortment in a dihybrid cross involving two heterozygous parents.

Describe the process of double fertilization.

Explain the steps involved in a polypeptide synthesis. How are the amino acids activated during polypeptide synthesis?

How is cardiac activity regulated?

Give schematic representation of nitrogen cycle and enlist important steps of this cycle.