Human Reproduction — BIOLOGY STD 12 Science — Question

Explain the different stages of oogenesis in humans starting from foetal life till its completion. When and where in the body is oogenesis completed?

State the law of independent assortment.

Diseases like dysentery, cholera, typhoid etc., are more common in over crowded human settlements. Why?

Differentiate between:

1. Predator and parasite.
2. S-Shaped and J-Shaped growth curve.

What are the factors which led to flourishing fishery industry in India?

For question 1-4, use this key:Key-

1. Ecology.
2. Population.
3. Community.
4. Ecosystem.

1. A community plus its physical environment.
2. Study of the interactions of organisms with each other and with the physical environment.
3. All populations that are found in a particular area.
4. All members of the same species that inhabit a particular area.

Write three important characteristics of population.

Answer the following questions:
Name the stages in a human female where:

1. Corpus luteum and placenta co–exist.
2. Corpus luteum temporarily ceases to exist.

Sakshi's father announced that the children are going to spend this weekend with their grandparents. During the journey, Sakshi saw some farmers who were spraying agrochemicals in their field. She requested her father to stop them. Her father praised her and contacted the farmers. He explained the side effects of such agrochemicals. He also suggested them to use biopesticides and biofertilisers instead of such chemicals. The farmers gave up spraying agrochemicals.

1. What did Sakshi's father explain to the farmers?
2. What are agrochemicals?
3. Why are biofertilisers or biopesticides preferred to chemical fertilisers or pesticides?
4. What values did Sakshi promote?

If a desired gene is identified in an organism for some experiments, explain the process of the following:
i. Cutting this desired gene at specific location.
ii. Synthesis of multiple copies of this desired gene.