Class 8 Reproduction In Animals Notes
Reproduction In Animals Notes
Reproduction is the ability of the living organism to produce young ones of their own kind.
Modes of Reproduction :-
- Asexual Reproduction
- Sexual Reproduction
Sexual Reproduction :-
The type of reproduction in which male and female Parents involved to give rise to an offspring is called sexual reproduction.
Male Reproductive Organs :-
Male Reproductive organs contains :
- A pair of testes( singular-testis ), Sperm ducts, urethra and a penis.
- Testis produce a male gamete called sperm.
- Sperm duct carry sperm to the penis.
- A sperm is unicellular has a head, a middle piece and a tail.
Female Reproductive Organs :-
Female reproductive organs contains :
- A pair of ovaries, oviduct (fallopian tubes) and uterus.
- Ovary produce female gametes called ova (eggs).
- A single natured egg is released into the oviduct by one of the ovaries every month.
- Uterus is the part where development of the baby takes place.
The fusion of male gamete (sperm) and female gamete (egg) is called fertilization.
During fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a
fertilized egg or zygote.
Internal fertilization :-
Fertilization which takes place inside the female body is called internal fertilization.
Internal fertilization occurs in many animals including humans, cows, dogs and hens.
External fertilization :-
Fertilization in which the fusion of a male and a female gamete takes place outside the body of the female is called external fertilization.
It is very common in aquatic animals such as fish, starfish, etc.
Development of Embryo :-
- 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.
Viviparous Animals :-
The animals which give birth to young ones are called viviparous animals.
Ex :- Human Beings, Dog, Cow etc.
Oviparous Animals :-
The animals which lay eggs are called oviparous animals.
Ex :- Hen, Frog etc.
The transformation of the larva into an adult through drastic changes is called metamorphosis.
Asexual Reproduction :-
The type of reproduction in which single parents involved to give rise to an offspring is called asexual reproduction.
Types of Asexual Reproduction :-
The reproduction in which the organism develops bulges called Buds. Since new individuals develops from buds. This type of asexual reproduction is known as budding.
Ex :- Hydra
Binary Fission :-
The type of asexual reproduction in which an animals reproduces by dividing into two individuals is called binary fission.
Ex :- Amoeba