Science (English Medium) इयत्ता १२ - CBSE Important Questions for Biology

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.

The wall layer of microsporangium, which nourishes the pollen grain, is ______.

Explain the menstrual phase in a human female. State the levels of ovarian and pituitary hormones during this phase.

Describe the roles of pituitary and ovarian hormones during the menstrual cycle in a human female.