Question

In humans at the end of the first meiotic division, the male germ cells differentiate into
A. Primary spermatocytes
B. Secondary spermatocytes
C. Spermatids
D. Spermatogonia

Answer 1

Hint:- Testes are the primary sex organs in males. These are oval in shape and are descended into the
scrotum which is an extra-abdominal sac. The male germ cells in the testes undergo meiotic division
leading to sperm formation.

Complete step-by-step solution:-
The site for spermatozoa formation is the seminiferous tubules of the testes. It includes two stages:
- Formation of spermatids
- Metamorphosis of spermatids
Spermatids are formed by three phases namely phase multiplication, growth and maturation.
Phase of multiplication involves mitosis. During phase of growth, the primary spermatocyte which is the
main germ cell, enlarges in size and prepares to undergo maturation division.
In the phase of maturation, the primary spermatocyte undergoes meiosis I, and gives rise to two haploid
(n) secondary spermatocytes. The secondary spermatocytes undergo meiosis II resulting in the
formation of spermatids.
A spermatid is non-motile and heavy. It has organelles like mitochondria, Golgi bodies, centrioles, etc.
During spermiogenesis the weight of the gamete is reduced and it also develops locomotory structures.
Nucleus becomes compact, forming the major part of the head of the spermatozoa. Golgi complex gives
rise to acrosome and the two centrioles of the spermatids become arranged one after the other behind
the nucleus.
Mitochondria from different parts of the spermatid get arranged in the middle piece around axial
filaments and much of the cytoplasm of the spermatid is lost.
The sperm of a mammal is flagellated, consisting of four parts namely head, neck, middle piece and tail.
So, the correct option is B.

Note:- The male gamete is a highly specialized structure. The main functions of sperms are to swim to the egg, fuse with the egg surface, to cause the egg to start its development and contribute the haploid component of the genome.