Ecosystems — BIOLOGY STD 12 Science — Question

1. Explain the development of female gametophyte from a megaspore mother cell in an angiosperm.
2. Draw a leballed diagram of a fully-developed embryo sac.

OR

1. Describe the process of megasporogenesis in angiosperms, until 8-nucleate stage.
2. Draw the labelled structure of mature embryo sac.

(i) Define the pollination.
(ii) Explain the process of double fertilization.
(iii) Draw a well labelled diagram of fertilized
embryo sac.

Anukool is a big businessman in Delhi, but belongs to a small village. He went to his village during Christmas holiday. He was very disturbed to see women still using cowdung's cakes to prepare food there. He decided to set up a biogas plant so that people can use gas obtained from it for cooking. The villagers were very thankful to Anukool for his valuable help.

1. What is biogas?
2. What are the uses of biogas?
3. Name some microorganisms involved in biogas production.
4. What are the values shown by Anukool?

Read the following and answer any four questions from (i) to (v) given below:
Apomixis is a mode of reproduction which does not involve formation of zygote through gametic fusion. In plants, apomixis commonly mimics sexual reproduction but produces seeds without fertilization. There are several methods of atomistic development in seeds. Thee two common ones are recurrent agamospermy and advective embryony.

1. Apomixis is a type of reproduction in plants, in which?

1. Fertilization does not take place.
2. Male nucleus takes part in fertilization.
3. Pollen fusion takes place.
4. Generative nucleus takes part in fertilization.

2. Which of the following statements is incorrect regarding recurrent agamospermy?

1. It is the formation of seed that has an embryo formed without meiosis and syngamy.
2. All the cells of embryo sac are diploid.
3. An embryo develops directly from a diploid cell other than egg like that of nucleus and integument.
4. None of these.

3. Adventive embryony is found in:

1. Citrus.
2. Opuntia.
3. Apple.
4. Both (a) and (b).

4. Formation of embryo directly from diploid egg without fertilization is called:

1. Apospory.
2. Diplospory.
3. Polyembryony.
4. Diploid parthenogenesis.

5. If any somatic cell of sporophyte produces gametophyte without reduction division, it is called:

1. Parthenogenesis.
2. Apogamy.
3. Apospory.
4. Amphimixis.

State the Mendelian principle which can be derived from such a cross and not from monohybrid cross.

Describe the experiment conducted by Hershey and Chase on the basis of the result obtained, write the condusion also.

Why is aerobic degradation more important than anaerobic degradation for the treatment of large volumes of waste waters rich in organic matter. Discuss.

Write an article on vaccination and immunization.

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

We are told that evolution is a continuing phenomenon for all living things. Are humans also evolving? Justify your answer.