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

"Biodiversity plays a major role in many ecosystem services that nature provides."

State one ethical reason for conserving biodiversity.

As a senior biology student you have been asked to demonstrate to the students of secondary level in your school, the procedure(s) that shall ensure cross-pollination in a hermaphrodite flower. List the different steps that you would suggest and provide reasons for each one of them.

Why do moss plants produce very large number of male gametes? Provide one reason. What are these gametes called?

Geitonogamous flowering plants are genetically autogamous but functionally cross-pollinated. Justify.

Describe the characteristic features of wind pollinated flowers.

Some organisms suspend their metabolic activities to survive in unfavourable conditions. Explain with the help of any four examples.

Why are some seeds referred to as apomictic seeds?

Angiosperms bearing unisexual flowers are said to be either monoecious or dioecious. Explain with the help of one example each.

A flower of tomato plant following the process of sexual reproduction produces 240 viable seeds.

Answer the following questions giving reasons :

(a) What is the minimum number of pollen grains that must have been involved in the pollination of its pistil?

(b) What would have been the minimum number of ovules present in the ovary?

(c) How many megaspore mother cells were involved?

(d) What is the minimum number of microspore mother cells involved in the above case?

(e) How many male gametes were involved in this case?

A non biology person is quite shocked to know that apple is a false fruit, mango is a true fruit and banana is a seedless fruit. As a biology student how would you satisfy this person?

Describe the development of endosperm after double fertilisation in an angiosperm.

A flower of tomato plant following the process of sexual reproduction produces 200 viable seeds.

Answer the following questions giving reasons :

(a) What would have been the minimum number of ovules present in pre-pollinated pistil ?

(b) How many microscope mother cells would minimally be required to produce requisite number of pollen grains ?

(c) How many pollen grains must have minimally pollinated the carple ?

(d) How many male gametes would have used to produce these 200 viable seeds ?

(e) How many megaspore mother cells were required in this process ?

Name the part of the flower which the tassels of the corn- cob represent.

Sketch and label stages in the development of the angiospermic female gametophyte from the functional megaspore.

Mention two strategies that evolved to prevent self-pollination in flowers.

List the three stages the annuals and biennial angiosperms have to pass through during their life cycle.

In a flowering plant a microspore mother cell produces four male gametophytes, while a megaspore mother cell forms only one female gametophyte. Explain.

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.