Science

Reproduction in Animals

• Importance of Reproduction

  • Reproduction is crucial for the continuation of a species.

  • It ensures the generation of similar individuals over time.

  • Without reproduction, extinction would be inevitable.

Modes of Reproduction

• Two main modes of reproduction in animals:

  1. Sexual Reproduction

  2. Asexual Reproduction

Sexual Reproduction

• Involves the fusion of male and female gametes (sperms and ova).

• Gametogenesis: Male and female reproductive organs produce gametes (sperms in males, ova in females).

• The fusion of gametes forms a zygote, marking the start of a new individual.

• Human Reproductive Organs:

  • Male organs: Testes (produce sperm), two sperm ducts, penis.

    1.Testes - Produce the male gametes called sperms .

    • Produces the male sex hormone, testosterone that causes puberty in males

    • Present in a pouch like structure called scrotum outside the male body to provide 1-3 °C less temperature than the body temperature for the production of a healthy sperm .

      2. Sperm ducts - Also known as vas deferens, these ducts transport sperm from the testes to the penis during ejaculation.

      3. Seminal Vesicles - These glands produce a fluid that nourishes the sperm and makes up a significant portion of semen, providing energy and facilitating sperm motility.

      4. Penis - Delivers sperms into the vagina of a female body

      5. Urethra- Carries semen or urine ouside the body.

  • Female organs: Ovaries (produce ova), oviducts (fallopian tubes), uterus.

    1. Ovaries- produce the female sex hormones , estrogen and progesterone .

       Also responsible for the production of female gamete, Ova or Egg.

    2. Uterus - A muscular organ where the fertilized egg implants and develops during pregnancy.

    3. Oviducts - The tubes that transport the ova from the ovaries to the uterus, playing a crucial role in fertilization as this is where sperm meets the egg.

    4. Vagina- A tube like structure that facilitates the movement of sperms into the female reproductive system and also acts as a birth canal along with the cervix .

Fertilisation

• Fertilisation: The process where a sperm and an ovum combine to form a zygote.

• Internal Fertilisation occurs within the female body (e.g., humans, cows).

• External Fertilisation happens outside the female body, often in water (e.g., fish, frogs).

  Frogs lay hundreds eggs in slow streams or ponds .

  The eggs are not covered by a hard shell instead a jelly like substance guards them

  The male frog releases sperms in the water and when sperms come in contact withthe eggs fertilization takes place .

Development of Embryo

• Zygote undergoes division and develops into an embryo.

• The embryo embeds in the uterine wall for further development, leading to a foetus

  foetus- the embryo who's parts can be identified.

• Gestation period - the period from fertilization to birth . In humans- 9 months or 40 weeks

• Paturation- The act of giving birth to a young one .

• Viviparous animals (e.g., humans) give birth to live young.

• Oviparous animals (e.g., birds, reptiles) lay eggs that develop into young.

Asexual Reproduction

• Involves one parent with offspring being genetically identical to the parent.

• Types of Asexual Reproduction:

  1. Budding: Seen in hydra, where new individuals develop as outgrowths from the parent.

  2. Binary Fission: Seen in amoeba, where the organism divides into two identical cells.

• Cloning: An advanced form of asexual reproduction where an exact genetic copy is produced (e.g., Dolly the Sheep).

Keywords

• Asexual reproduction

• Binary fission

• Budding

• Eggs

• Embryo

• External fertilisation

• Fertilisation

• Foetus

• Internal fertilisation

• Metamorphosis

• Oviparous animals

• Sexual reproduction

• Sperms

• Viviparous animals

• Zygote

What You Have Learned

• Two modes of reproduction: Sexual and Asexual.

• Sexual reproduction involves the fusion of male and female gametes.

• The development of the embryo and its transition to a foetus occurs in the uterus for viviparous animals.

• Asexual reproduction leads to the formation of genetically identical offspring without gamete fusion.

• Understanding reproductive processes helps in understanding the growth and development of various

• species, as well as the evolutionary strategies that have emerged in different environments.

Important Questions

1. What are the two main modes of reproduction in animals?

2. Describe the process of fertilization and differentiate between internal and external fertilization.

3. Explain the significance of gestation periods in viviparous animals.

4. What are the roles of male and female reproductive organs in sexual reproduction?

5. Define asexual reproduction and name its different types.

6. How does binary fission differ from budding in asexual reproduction?

7. What is cloning, and how does it relate to asexual reproduction?

8. Discuss the importance of reproduction for the continuation of a species.

9. What are viviparous and oviparous