Q44. How does fertilization take place in frog?
How do frog eggs get fertilized?
How does fertilization occur in frog?
Ans. During spring or rainy season, frogs and toads
move to ponds and slow flowing streams. When the male and female come together
in water, the female lays hundreds of eggs. Frog’s egg is not covered
by a shell and it is comparatively very delicate. A layer of jelly holds the
eggs together and provides protection to the eggs. As the eggs are laid, the
male deposits sperms over them. Each sperm swims randomly in water with the help
of its long tail. The sperms come in contact with the eggs. This results in
Q45. What is ‘in vitro fertilization’ technique of reproduction?
What are test-tube babies?
In some women oviducts are blocked. These women are unable to bear babies
because sperms cannot reach the egg for fertilization. In such cases, doctors collect
freshly released egg and sperms and keep them together for a few hours for IVF
or in vitro fertilization (fertilization outside the body). In case
fertilization occurs, the zygote is allowed to develop for about a week and
then it is placed in the mother’s uterus. Complete development takes place in
the uterus and the baby is born like any other baby. Babies born through this
technique are called test-tube babies.
Q46. How could a single cell become such a big individual?
Ans. Fertilization results in the formation of zygote.
The zygote divides repeatedly to give rise to a ball of cells. The cells then
begin to form groups that develop into different tissues and organs of the
body. This developing structure is termed an embryo. The embryo gets embedded
in the wall of the uterus for further development. The embryo continues to
develop in the uterus. It gradually develops the body parts such as hands, legs,
head, eyes, ears, etc. The stage of the embryo in which all the body parts can
be identified is called a foetus. When the development of the foetus is complete,
the mother gives birth to the baby.
Q47. What are the steps involved in sexual reproduction in
Ans. Steps involved in sexual
reproduction in animals are:
The male parent produces male gametes
called sperms. Sperm is a single cell with all the usual
The female parent produces female gametes
called eggs (or ova). Like the sperm, an egg is also a single cell.
The sperm enters into the egg. The nucleus
of sperm fuses with the nucleus of egg cell to form a new cell called zygote.
The zygote divides repeatedly to form a
hollow ball of hundreds of cells which is called embryo.
Embryo grows and becomes a foetus in which
all main body features of the baby animal have formed.
Foetus grows and develops to form a new
Q48. How does an amoeba reproduce?
Ans. Amoeba is a single-celled organism. It begins the
process of reproduction by the division of its nucleus into two nuclei. This is
followed by division of its body into two, each part receiving a nucleus.
Finally, two amoebae are produced from one parent amoeba.
Image from NCERT