Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

What is population explosion? Discuss the various reason of population explosion.

Describe the roles of pitutary and ovarian hormones during the menstrural cycle in human female.###Explain the various phases of menstrual cycle. Give a diagrammatic representation of various events during a menstrual cycle.

a. Where is microsporangium located in an angiosperm? State the functions of tapetum and the other three layers of microsporangium.
b. Describe the structure of the male gametophyte produced as a result of microsporogenesis.
c. State the functions of each part of the male gametophyte.

Where does spermatogenesis occur in human testes? Describe the process of spermatogenesis upto the formation of spermatozoa.

A pea plant bearing axial flowers is crossed with a pea plant bearing terminal flowers. The cross is carried out to find the genotype of the pea plant bearing axial flowers. Work out the cross to show the conclusions you arrive at.

(a) Briefly explain the events of fertilization and implantation in an adult human female.
(b) Comment on the role of placenta as an endocrine gland.

a. Why did Hershey and Chase use radioactive ³²P and ³⁵S in their experiments? Explain.
b. Following the experiments conducted by them, write what conclusion did they arrive at and how.

Explain the embryonic development upto blastula formation in human ?###Draw a labelled diagram of blastocyst formation.###Define Cleavage ? Explain the development of the zygote upto blastocyst formation.

Describe the functions of the following:
Trophoblast.