Q22 of 50 Page 1

Draw a labelled diagram of the sectional view of a human seminiferous tubule (six parts to be labelled)


1. Spermatozoa: It is the male sex cell that fertilises with ovu, to form a zygote.


2. Spermatid: It is a haploid male gamete formed by the division of secondary spermatocyte.


3. Secondary spermatocyte: These are haploid (n) cells formed by the meiotic division of primary spermatocytes.


4. Primary Spermatocyte: These are diploid (2n) cells which by meiotic division give rise to secondary spermatocytes.


5. Sertoli cell: These cells are present in the seminiferous tubules and helps in the nourishment of the spermatozoa.


6. Spermatogonium: It is an undifferentiated male germ cell it undergoes maturation to form mature spermatozoa.


Cells.PNG


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A cross between a normal couple resulted in a son who was haemophilic and a normal daughter. In course of time, when the daughter was married to a normal man, to their surprise, the grandson was also haemophilic.

(a) Represent this cross in the form of a pedigree chart. Give the genotypes of the daughter and her husband.


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(ii) State the relation between gross and net primary productivity.


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OR

(a) Why does endosperm development precede embryo development in angiosperm seeds? State the role of endosperm in mature albuminous seeds.


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