Sexual Reproduction in Animals

• Reproduction is essential for the continuation of species.

Modes of Reproduction

• Animals reproduce through sexual and asexual modes.

Sexual Reproduction

• Involves the fusion of male and female gametes (sex cells).
• Offspring inherit genetic material from both parents, leading to variations.

Male Reproductive System

• Consists of testes, sperm ducts, and a penis.
• Testes produce male gametes called sperm.
• Sperm are motile and much smaller than the female gamete.

Female Reproductive System

• Consists of ovaries, oviducts (fallopian tubes), and a uterus.
• Ovaries produce female gametes called ova (eggs).
• In human females, a single mature egg is released into the oviduct every month.
• The uterus is where the development of the baby occurs.

Fertilization

• The process of fusion of a sperm and an ovum is called fertilization.
• Occurs in the oviduct.
• The fertilized egg is called a zygote.

Types of Fertilization

• Internal Fertilization: Occurs inside the female body (e.g., humans, cows, hens).
• External Fertilization: Occurs outside the female body (e.g., frogs, fish).
• Frogs lay eggs in water, and sperm are released over them.
• The fusion of gametes occurs externally in water.

Development of the Zygote

• The zygote divides repeatedly to form a ball of cells called an embryo.
• The embryo implants in the wall of the uterus for further development.

Embryo Development

• The embryo gradually develops body parts like hands, legs, head, eyes, etc.
• The stage of the embryo in which all the body parts are identifiable is called a fetus.

Viviparous and Oviparous Animals

• Viviparous Animals: Animals that give birth to young ones (e.g., humans, cows).
• Oviparous Animals: Animals that lay eggs (e.g., hens, frogs).
• In oviparous animals, the fertilized egg develops into an embryo inside the egg, which then hatches.

From Egg to Young One

• In hens, after fertilization, the zygote divides repeatedly and travels down the oviduct.
• As it travels, protective layers form around it, the hard shell is one such layer.
• Once the hard shell is formed, the hen lays the egg.
• The embryo takes about 3 weeks to develop into a chick.

Metamorphosis

• The transformation of the larva into an adult through drastic changes is called metamorphosis.
• Example: Frog – Egg → Tadpole → Adult Frog.
• Tadpoles look very different from adult frogs and live in water.
• They undergo metamorphosis to become adults capable of jumping on land.
• Insects like silkworms and butterflies also undergo metamorphosis.

Asexual Reproduction

• Reproduction without the fusion of gametes.

Types of Asexual Reproduction

• Budding: A new individual develops from a bud on the parent's body (e.g., Hydra).
• Binary Fission: An organism divides into two identical individuals (e.g., Amoeba).

Budding in Hydra

• Small outgrowth called a bud develops on the side of its body.
• The bud gradually grows and develops into a new individual.
• Eventually detaches from the parent and lives as an independent organism.

Binary Fission in Amoeba

• The nucleus of Amoeba divides into two.
• The cytoplasm divides, and the cell splits into two daughter cells.
• Each daughter cell receives a nucleus and grows into an independent Amoeba.

Cloning

• Production of an exact copy of a cell, any other living part, or a complete animal.
• Dolly the sheep was the first mammal to be cloned.
• Cloned animal is exactly similar to the parent.

Explore animal reproduction: sexual reproduction, male and female reproductive systems, fertilization, and zygote formation. Understand the roles of testes, ovaries, sperm, and ova in the reproductive process. Learn about internal and external fertilization.