Sexual Reproduction in Flowering Plants — BIOLOGY STD 12 Science — Question

What is vector? Which cloning vector was discovered first?

During reproduction, the chromosome number (2n) reduces to half (n) in the gametes and again resume the original number (2n) in the offspring, what are the processes through which these events take place?

Explain the roles of the following with the help of an example each in recombinant DNA technology:

1. Restriction Enzymes.
2. Plasmids.

The following graph represents the organismic response to certain environmental condition (e.g. temperature):

1. Which one of these, 'a' or 'b', depicts conformers?
2. What does the other line graph depict?
3. How do these organisms differ from each other with reference to homeostasis?
4. Mention the category to which humans belong.

What are carcinogens? Describe their categories.

What is the role of cervix of the human female system in reproduction?

Your school has been selected by the Department of Education to organise and host an interschool seminar on 'Reproductive Health-Problems and Practices'. However, many parents are reluctant to permit their wards to attend it. Their argument is that the topic is 'too embarrassing'. Put forth four arguments with appropriate reasons and explanations to justify the topic to be very essential and timely.

State what is apomixis. Comment on its significance. How can it be commercially used?

Explain three basic steps to be followed during genetic modification of an organism.

State the views of Oparin and Haldane on evolution. How does S.L. Miller's experiment support their views?

OR

1. Explain the theory of abiogenesis.
2. How did Miller demonstrate experimentally the chemical evolution that happened three billion years ago?