Evolution — BIOLOGY STD 12 Science — Question

Describe various methods of contraception for the population control.###What are the main types of methods of birth control?###Discuss use of Various Contraceptive measures used for population.

What are ecological pyramids? Mention its limitations.

What is nucleosome. Draw a labelled diagram of nucleosome. Explain the structures of DNA helix.

a. How did Meselson and Stahl reach the conclusion that DNA replication is semi-conservative while working with E. coli in their experiment?
b. Explain the contribution of Taylor and his colleagues in DNA replication in flowering plants.

What is meant by the term bio-pesticide? Name and explain the mode of action of a popular bio-pesticide.

Give the term/ reason:
Sperm cannot reach ovum without seminal plasma.

Describe the law of independent by using punnet's square.

Vicky's mother was using the same mosquito repellent cream from last six years. She was regularly complaining that this cream has no effects on mosquitoes now. Hearing this, Vicky advised his mother to change the cream as regular usage has led the mosquitoes to develop resistance against it. His mother changed the cream and could notice its effect on mosquitoes.

1. Explain how mosquitoes were not affected by the previous cream?
2. On what factors, Darwin's theory was based?
3. Can you relate this incident to Darwin's concept? How?
4. Identify the values shown by Vicky.

State the similarity and differences between geitonogamy and xenogamy. Why do cleistogamous flowers assure seed sets?

Give a schematic labelled diagram to represent oögenesis (without descriptions)