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VIII-9-Reproduction in animals.pptx

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1. Reproduction is the process by which new individuals are produced of the same species. There are two modes of reproduction: asexual and sexual. 2. In sexual reproduction, gametes from two parents (a male sperm and female egg) fuse to form a zygote through fertilization. The zygote then develops into a new individual with traits from both parents. 3. Fertilization can occur internally within the female body or externally outside the female body, depending on the species. After fertilization, the fertilized egg undergoes cell division and develops into an embryo and fetus before birth or hatching.

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CHAPTER - 9 REPRODUCTION IN ANIMALS CLASS :- VIII SUBJECT :- SCIENCE
1) Reproduction :- Reproduction is the process by which new individuals of the same species are produced. Reproduction is important for the continuation of similar kinds of individuals for generations. 2) Modes of reproduction :- There are two modes of reproduction. They are :- i) Asexual reproduction ii) Sexual reproduction In asexual reproduction new individuals are produced from a single parent. In sexual reproduction two parents are needed to produce new individuals. In sexual reproduction a male gamete fuses with a female gamete to form a zygote which later develops into a new individual.
3) Sexual reproduction :- a) Male reproductive system :- • The main reproductive organs in humans consists of a pair of testes (singular testis), two sperm ducts and a penis. • The testes produces the male gametes called sperms. • The testes produces millions of sperms. A sperm is a single cell. • The sperm has a head, a middle piece and a tail. Male reproductive organs Human sperm
b) Female reproductive organs :- • The female reproductive organs consists of a pair of ovaries, a pair of oviducts (fallopian tubes) and uterus. • The ovary produces the female gametes called ova (eggs). • A single egg is produced by the ovary every month. The egg is a single cell. Human ovum (egg) Female reproductive organs
4a) Fertilsation :- The fusion of the sperm and ovum (egg) is called fertilisation. The fertilised egg is called zygote. The fertilised egg then develops into a new individual. Since the sperm from the father fuses with the egg from the mother, the new individual inherits some characters from the father and some from the mother. Fertilised egg
b) Types of fertilisation :- Fertilisation is of two types. They are :- i) Internal fertilisation ii) External fertilisation In internal fertilisation the fertilisation takes place inside the female body. Eg :- humans, cows, dogs, hens etc. In external fertilisation the fertilisation takes place outside the female body. Eg:- frogs, fishes, starfish etc.
5) Development of embryo :- After fertilisation the fertilised egg divides to form a group of cells called the embryo. The embryo then attaches to the wall of the uterus and then develops the body parts like hands, legs, head, eyes, ears .This is called foetus. When the development of the foetus is complete the mother gives birth to the baby. Animals which give birth to their young ones are called viviparous animals. Eg:- humans, dog, cow, cat etc. Animals which lay eggs are called oviparous animals. Eg:- frog, fish, butterfly, lizard etc
6) Life cycle of animals :- Some animals show different stages in their life cycles. Eg:- The stages in the life cycles of silk worm, butterfly etc. are:- Egg Larva Pupa Adult (Caterpillar) The stages in the life cycle of frog are:- Egg Larva Adult (Tadpole) The transformation of the larva into an adult is called metamorphosis.
7) Asexual reproduction :- Asexual reproduction in some organisms takes place by different methods like budding, binary fission etc. Budding :- In this method a small bulge develops from the body called bud. The bud then grows and develops into a new individual. Eg: Hydra, Yeast etc. Binary fission :- In this method the nucleus first divides and forms two nuclei. Then the cytoplasm also divides into two parts and forms two daughter cells. Eg :- Amoeba, Paramaecium etc. Budding in hydra Binary fission in amoeba

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VIII-9-Reproduction in animals.pptx

  • 1. CHAPTER - 9 REPRODUCTION IN ANIMALS CLASS :- VIII SUBJECT :- SCIENCE
  • 2. 1) Reproduction :- Reproduction is the process by which new individuals of the same species are produced. Reproduction is important for the continuation of similar kinds of individuals for generations. 2) Modes of reproduction :- There are two modes of reproduction. They are :- i) Asexual reproduction ii) Sexual reproduction In asexual reproduction new individuals are produced from a single parent. In sexual reproduction two parents are needed to produce new individuals. In sexual reproduction a male gamete fuses with a female gamete to form a zygote which later develops into a new individual.
  • 3. 3) Sexual reproduction :- a) Male reproductive system :- • The main reproductive organs in humans consists of a pair of testes (singular testis), two sperm ducts and a penis. • The testes produces the male gametes called sperms. • The testes produces millions of sperms. A sperm is a single cell. • The sperm has a head, a middle piece and a tail. Male reproductive organs Human sperm
  • 4. b) Female reproductive organs :- • The female reproductive organs consists of a pair of ovaries, a pair of oviducts (fallopian tubes) and uterus. • The ovary produces the female gametes called ova (eggs). • A single egg is produced by the ovary every month. The egg is a single cell. Human ovum (egg) Female reproductive organs
  • 5. 4a) Fertilsation :- The fusion of the sperm and ovum (egg) is called fertilisation. The fertilised egg is called zygote. The fertilised egg then develops into a new individual. Since the sperm from the father fuses with the egg from the mother, the new individual inherits some characters from the father and some from the mother. Fertilised egg
  • 6. b) Types of fertilisation :- Fertilisation is of two types. They are :- i) Internal fertilisation ii) External fertilisation In internal fertilisation the fertilisation takes place inside the female body. Eg :- humans, cows, dogs, hens etc. In external fertilisation the fertilisation takes place outside the female body. Eg:- frogs, fishes, starfish etc.
  • 7. 5) Development of embryo :- After fertilisation the fertilised egg divides to form a group of cells called the embryo. The embryo then attaches to the wall of the uterus and then develops the body parts like hands, legs, head, eyes, ears .This is called foetus. When the development of the foetus is complete the mother gives birth to the baby. Animals which give birth to their young ones are called viviparous animals. Eg:- humans, dog, cow, cat etc. Animals which lay eggs are called oviparous animals. Eg:- frog, fish, butterfly, lizard etc
  • 8. 6) Life cycle of animals :- Some animals show different stages in their life cycles. Eg:- The stages in the life cycles of silk worm, butterfly etc. are:- Egg Larva Pupa Adult (Caterpillar) The stages in the life cycle of frog are:- Egg Larva Adult (Tadpole) The transformation of the larva into an adult is called metamorphosis.
  • 9. 7) Asexual reproduction :- Asexual reproduction in some organisms takes place by different methods like budding, binary fission etc. Budding :- In this method a small bulge develops from the body called bud. The bud then grows and develops into a new individual. Eg: Hydra, Yeast etc. Binary fission :- In this method the nucleus first divides and forms two nuclei. Then the cytoplasm also divides into two parts and forms two daughter cells. Eg :- Amoeba, Paramaecium etc. Budding in hydra Binary fission in amoeba