Page 97 - Science Class 08

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Reproduction in Animals
• Methods of Reproduc on
• Bisexual and nisexual organism U s
• Reproduc on in Humans
• Asexual Reproduc on
Reproduc on is defined as the process of
producing young ones. The process of reprodu-
c on is not essen al for the survival of an
individual, but reproduc on is essen al for the
con nua on of a species.
The benefits of reproduc on are as follows:
v Reproduc on ensures con nuity of life on
the earth.
v Reproduc on acts as a bridge to hereditary
transmission.
v It involves con nua on of characters from
the parents to daughter cells by copying of
DNA (Deoxyribonucleic Acid) molecules
present in the chromosomes of the cell.
v Copying of DNAs is also not a foolproof
exercise, even minute changes bring about
varia on in the blueprint of the offsprings.
v The useful varia ons are retained while the
harmful ones do not go beyond.
v Actually, varia ons help the species to
withstand dras c environmental changes,
Science-8
• Sexual Reproduc on
• Fer lisa on
• Test Tube Babies
thus, save the species from becoming
ex nct and promote their survival for a
longer me.
v This inbuilt tendency of varia on is the
“fuel” for evolu on.
METHODS OF REPRODUCTION
Some animals give birth to their babies, some
animals lay eggs which hatch to give babies,
some offsprings grows out of their parents
body like hydra and some unicellular organisms
like amoeba simply splits into two. Thus, there
are different methods of reproduc on.
These methods can be categorised into two
broad methods of reproduc on:
v Sexual Reproduc on
v Asexual Reproduc on
SEXUAL REPRODUCTION
In sexual reproduc on, two parents one male
and the other female of the same specie are
required. Each parent produces a reproduc ve
cell or gamete. Thus, we can say that sexual
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