Class 8 Reproduction In Animals Notes

Reproduction In Animals Notes

Reproduction :-

Reproduction is the ability of the living organism to produce young ones of their own kind.

Modes of Reproduction :-

1. Asexual Reproduction
2. 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.

Fertilization :-

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.

Metamorphosis :-

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 :-

Budding :-

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