Reproduction in Living Organisms

Reproduction

• Reproduction is the process by which living organisms produce new organisms like themselves.
• Tigers, hens, mango trees, bacteria, Paramecium, and Amoeba all reproduce.
• Reproduction ensures the continuation of species.

Modes of Reproduction

• Two main types: asexual and sexual reproduction.

Asexual Reproduction

• Involves only one parent.
• Binary Fission: A single-celled organism divides into two, with the genetic material dividing first.
• Budding: New organisms grow as buds on the parent, then detach. (e.g., Hydra, sponges, sea anemones)
• Fragmentation: An organism's body breaks into pieces, with each piece developing into a new organism. (e.g., Planaria, some flatworms)

Sexual Reproduction

• Involves two parents.
• Most plants and animals reproduce sexually.
• Many animals have separate male and female individuals.
• Some animals (e.g., earthworms, garden snails) are hermaphrodites, possessing both male and female reproductive systems.

Gametes

• Specialized cells involved in sexual reproduction:
• Sperm (male gamete)
• Egg (female gamete)
• Their function is to produce a new organism

Fertilization

• Fusion of sperm and egg nuclei.
• External Fertilization: Occurs outside the body (e.g., frogs, many fish). The female releases eggs, male releases sperm, fertilization occurs in water.
• Internal Fertilization: Occurs inside the female reproductive system. (e.g., land animals, birds, mammals). Critical for animals that live in dry environments.

Oviparous Animals

• Lay eggs.
• Examples include insects (butterflies, moths, mosquitoes, grasshoppers), many reptiles, and all birds.
• Develops inside the egg.
• Young one hatches from egg
• Some undergo metamorphosis (e.g., caterpillar to pupa to butterfly)

Viviparous Animals

• Give birth to live young.
• Examples include all mammals (except platypuses and echidnas).
• Fertilization is internal, and the new individual develops inside the female's body.

Human Reproduction

• Separate male and female systems.

Male Reproductive System

• Testes: Produce sperm
• Sperm ducts
• Penis

Female Reproductive System

• Ovaries: Produce ova (eggs)
• Fallopian tubes
• Uterus

Fertilization and Embryo Development

• Sperm penetrates egg and nuclei fuse.
• Fertilized egg (zygote)
• Zygote moves to the uterus.
• Implantation in uterine wall (forming placenta)
• Developing zygote becomes embryo.
• Embryo enclosed in amnion (filled with amniotic fluid).
• Embryo matures into fetus.

Fetus Nourishment

• Umbilical cord connects fetus to placenta
• Placenta is attached to the uterine wall, provides nutrients & oxygen to fetus and removes waste.

Post-Birth

• Newborn infant depends on mother's milk.
• Proper nutrition crucial for both mother and child during pregnancy and breastfeeding.
• Malnutrition during pregnancy or breastfeeding can lead to health problems.