Science (English Medium) Class 12 - CBSE Important Questions

Read the statement and answer the questions that follow.

A flower of brinjal has 520 ovules in its ovary. However, it produces a fruit with only 480 viable seeds.

(a) What could have prevented the rest of the 40 ovules from maturing into viable seeds? Explain giving a reason.

(b) Describe the development of a dicot embryo in a viable seed.

(c) Why certain angiospermic seed albuminous while others are exalbuminous? Explain.

A capsicum flower has 240 ovules in its ovary. But, it produces a fruit with only 180 viable seeds.
 

Draw a diagram of a section of a megasporangium of an angiosperm and label funiculus, Micropyle, embryosac and nuclleus.

Why does endosperm development preceeds that of zygote ?

Describe the development of an endosperm in a viable seed. Why does endosperm development precedes embryo development?

Give an example of an angiosperm seed that has a perisperm. Name the part the perisperm develops from.

Compare the characteristic features of insect pollinated and wind pollinated flowers. Explain how the respective features assist in pollination.

Answer the following question.
You are conducting artificial hybridization on papaya and potato. Which one of them would require the step of emasculation and why? However, for both, you will use the process of bagging. Justify giving one reason.

Answer the following question.
Express the process of pollination in Vallisneria.

Differentiate between geitonogamy and xenogamy (allogamy).

Answer the following question.
Write the difference in the characteristics of the progeny produced as a result of the two processes.

Can a plant flowering in Mumbai be pollinated by pollen grains of the same species growing in New Delhi? Provide explanations to your answer.

Answer the following question.
When a seed of orange is squeezed, many embryos, instead of one are observed. Explain how it is possible.

Coelacanth was caught in South Africa. State the significance of the discovery of Coelacanth in the evolutionary history of vertebrates.

Emasculation and bagging are the two important steps carried during artificial hybridization to obtain superior varieties of desired plants. Explain giving reasons, in which types of flowers and at what stages are the two processes carried out.

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

1. Nucellus
2. Antipodals
3. Synergids
4. Micropyle

Flowers which have single ovule in the ovary and are packed into inflorescence are usually pollinated by ______.

Assertion: Apomictic embryos are genetically identical to the parent plant.

Reason: Apomixis is the production of seeds without fertilization.

Trace the development of a megaspore mother cell to the formation of a mature embryo sac in a flowering plant.