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Sexual Reproduction in Animals:
Most animals reproduce sexually
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Formation of Gametes (Gametogenesis):
The formation of gametes is called
gametogenesis
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The male and
female gametes (sperms and egg cells or ova)
are produced in specialized organs called
gonads
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The production of sperms in
testes is called spermatogenesis and the
production of egg cells in ovaries is called
oogenesis (as per below fig)
Spermatogenesis:

Some cells present in the walls of the
seminiferous tubules of testes divide
repeatedly by mitosis to form large number of
diploid spermatogonia
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Each
primary spermatocytes undergoes meiosis-I
and produces two haploid daughter cells
called secondary spermatocytes
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In this way four haploid
spermatids are produced from each primary
spermatocyte
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Their nuclei shrink and
some structures are formed e
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After these changes, the spermatids are
called sperms
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Some oogonia produce diploid
primary oocytes
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The smaller cell is called first
polar body and the large one is called
secondary oocyte
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e a secondary polar body and
an egg cell

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