NAVODAYA VIDYALAYA SAMITI, NOIDA
e-Content Preparation
CLASS: VIII SCIENCE
Unit: 9. Reproduction
in Animals
SARALA MI, TGT SCIENCE,
JNV TRIVENDRUM, KERALA
At the end of this chapter the pupil will be able to:
system
life cycle of frog, binary fission in amoeba etc.
from experiences.
Learning outcomes and Goals
Topics to be covered
Reproduction is a process by which an organism produces offsprings that are biologically or genetically similar to the parent organism
Reproduction in animals is of two types –
Reproduction in animals
Sexual reproduction is the process in which new organisms are created by combining the genetic information from two individuals of different sexes.
In higher animals a specialised Reproductive System helps in carrying out sexual reproduction
Sexual Reproduction
Male Reproductive System
It consists of a pair of testes, sperm ducts and penis. The testes produce numerous male gametes called sperm. Sperms are carried through sperm ducts to the urethra which passes through muscular penis.
Sperm is a microscopic, motile, male reproductive cell or gamete composed of a head, middle piece and tail. The tail helps sperms in swimming. The sperm helps in transferring the genetic material to the female body during the mating.
Sperm
Female Reproductive System
It consists of a pair of ovaries, oviducts (fallopian tubes) and uterus. The ovary produces the female gamete called ovum or egg. The oviduct collects the ovum and passes it to the hollow muscular structure called uterus. The lower side of the uterus is called cervix. A narrow muscular passage called vagina connects the outside with uterus
Ovum or egg cell is a microscopic, female reproductive cell or gamete. Each ovum is a rounded and non-motile structure. Egg is much larger than the sperm.
Ovum
Fertilisation
Fertilisation is the process of fusion of the sperm and the ovum (egg). The nucleus of the sperm fuses with the nucleus of the ovum to form a zygote or fertilised egg
The type of fertilisation in which the fusion of sperm and ovum takes place inside the female body is known as internal fertilisation. Eg. Human beings, cat , lion, snake , birds ,deer etc.
Internal Fertilisation
The process of releasing the eggs and sperms into the water by frogs and fishes is termed spawning
Hundreds of eggs are produced by the female frog at a time. The eggs are delicate and are protected by a jelly like envelope
Spawning
The type of fertilisation in which the fusion of
sperm and ovum/egg occurs outside the female body is called external fertilisation. Eg. Fish, frog, starfish, sea anemone, sea urchin, coral etc.
External Fertilisation
In-vitro fertilisation (IVF) is a process of fertilisation
where an egg is combined with sperm outside the body (in glass test tube). After the fertilisation the embryo is deposited in same or another woman's uterus for successful pregnancy.
In- Vitro Fertilisation
Embryonic development in Human
Zygote Embryo Foetus
Embryonic development in Hen
The animals which undergo internal fertilisation and later give birth to young ones are called viviparous animals. Eg. Human beings, elephant, dog, giraffe, zebra, tiger etc.
The animals which undergo internal fertilisation and later lay eggs which hatch into young ones are called oviparous animals. Eg. Snakes, insects, birds, lizards tortoise, turtle etc.
Metamorphosis
Frogs have multiple stages in their life cycle such as egg, tadpole, tadpole with legs, froglet and frog. The drastic changes taking place during the development of egg into an adult is termed metamorphosis
Asexual Reproduction
Asexual reproduction is a type of reproduction which does not involve the fusion of gametes.The offspring that arise by asexual reproduction from a single cell or from a multicellular organism inherit the genes of that parent.
Budding in Hydra
Hydra develops a bud on its tubular body. The bud grows in size and gets detached from the parent hydra. The newly formed hydra is called daughter hydra. This type of asexual reproduction in hydra is termed budding.
Binary Fission in Amoeba
The nucleus of the amoeba divides into two followed by the division of the cell. Each daughter amoeba receives one nucleus. The process of producing new amoebae by splitting the parent amoeba into two is termed binary fission.
Cloning is a process of generating a genetically identical copy of a cell or any other body part or a complete organism.
Cloning
Cloning of Dolly
1. What is the function of sperm?
2. Where does fertilisation take place in fish ?
3. Why do female frogs produce hundreds of eggs at a time?
4. What is the difference between frog’s egg and hen’s egg?
5. Mention some examples of oviparous animals.
6. What is common between budding and binary fission?
Recapitulation
THANK YOU