2.1 Reproduction in Plants and Animals

Reproduction: Overview

• Biological process by which new individual organisms (offspring) are produced from parents.
• Fundamental feature of all life.
• Two main forms: Asexual and Sexual.

Plants: Asexual Reproduction

• Involves a single parent; offspring are genetically identical.
• Methods:
  • Binary Fission: Parent cell splits into two (e.g., Bacteria).
  • Budding: New individual develops from parent (e.g., Yeast, Potatoes).
  • Fragmentation: Organism splits into fragments, each grows into new individual (e.g., Spirogyra).
  • Spore Formation: Produces spores that grow into new organisms (e.g., Fungi, Ferns).
  • Vegetative Propagation: New plants from vegetative parts (roots, stems, leaves) (e.g., Potato, Strawberry).
  • Artificial Propagation (Tissue Culture): Growing new plants from small tissue pieces (e.g., Orchids).
  • Apomixis: Seed production without fertilization (e.g., Dandelions).

Plants: Sexual Reproduction

• Involves fusion of male and female gametes; results in genetic diversity.
• Occurs in the flower.
• Flower Parts: Calyx (sepals), Corolla (petals), Androecium (stamens - male), Gynoecium (carpels/pistil - female).
• Pollination: Transfer of pollen from anther to stigma.
  • Self-Pollination: Within same flower/plant.
  • Cross-Pollination: Between different plants of same species.
• Agents of Pollination: Insects, Water, Wind.

Plants: Fertilization

1. Pollen grain lands on stigma.
2. Pollen tube grows down to ovule.
3. Male gamete travels down pollen tube and fuses with female gamete (egg) in ovule to form a zygote.
4. Zygote develops into an embryo within a seed.
5. Ovary develops into a fruit protecting the seed.

• Artificial Pollination: Manual transfer of pollen.

Animals: Asexual Reproduction

• More common in invertebrates.
• Methods:
  • Fission: Parent splits into two or more individuals (e.g., Sea anemones).
  • Budding: New individual grows from parent's body (e.g., Hydras).
  • Fragmentation: Body breaks into pieces, each grows into new adult (e.g., Planarians).
  • Parthenogenesis: Egg develops without fertilization (e.g., some insects, reptiles).

Animals: Sexual Reproduction (Humans)

• Involves fusion of male (sperm) and female (egg) gametes.
• Male Reproductive System: Testes (sperm, testosterone), Scrotum, Epididymis, Vas Deferens, Urethra, Penis, Accessory Glands.
• Female Reproductive System: Ovaries (eggs, estrogen), Fallopian Tubes, Uterus, Cervix, Vagina.

Animals: Fertilization and Development

• Fertilization: Fusion of sperm and egg.
  • External Fertilization: Gametes released into environment (e.g., Fish).
  • Internal Fertilization: Sperm deposited directly into female tract (e.g., Humans, terrestrial animals).
• Development: Zygote develops into embryo.
  • Oviparity: Embryo develops in egg laid outside (e.g., Birds).
  • Viviparity: Embryo develops inside female, nourished by her (e.g., Humans).