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

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.

When and where do chorionic villi appear in humans?

Explain the role of pituitary and the ovarian hormones in menstrual cycle in human females

During the reproductive cycle of a human female, when, where and how does a placenta develop? What is the function of placenta during pregnancy and embryo development?

Describe the changes that occur in ovaries and uterus in human female during the reproductive cycle.

Name the function of the following:

Corpus luteum

Arrange the following hormones in sequence of their secretion in a pregnant woman. Mention their source and the function they perform:

hcG, LH, FSH, Relaxin

Why is follicular phase in the menstrual cycle also referred as proliferative phase? Explain.

Explain the events that occur in a graafian follicle at the time of ovulation and thereafter.

State the Function of Chorionic Villi

Explain the ovarian and uterine events that occur during a menstrual cycle in a human female under the influence of pituitary and ovarian hormones respectively.

Explain the changes that occur in the ovary and uterus during menstrual cycle in human females. Mention the influence of pituitary and ovarian hormones in bringing these changes.

In the figure given below, parts A and B show the level of hormones which influence the menstrual cycle. Study the figure and answer the questions that follow:

1. Name the organs which secrete the hormones represented in parts A and B.
2. State the impact of the hormones in part B on the uterus of the human female during 6 to 15 days of the menstrual cycle.