REPRODUCTION AND EMBRYONIC DEVELOPMENT IN PLANTS AND ANIMALS

I. REPRODUCTION IN PLANTS

Plants reproduce through sexual and asexual reproduction.

A. Sexual Reproduction in Plants

• Involves the fusion of male and female gametes to produce genetically diverse offspring.

• Occurs in flowering plants (angiosperms) and non-flowering plants (gymnosperms, ferns, mosses).

1. Parts of a Flower (Reproductive Structures of Angiosperms)

• Stamen (Male Part)

  • Anther – Produces pollen (contains male gametes).

  • Filament – Supports the anther.

• Pistil/Carpel (Female Part)

  • Stigma – Receives pollen.

  • Style – Tube that connects stigma to ovary.

  • Ovary – Contains ovules (female gametes), develops into fruit after fertilization.

• Petals – Attract pollinators.

• Sepals – Protect the bud before blooming.

2. Fertilization in Angiosperm

• Pollination: Transfer of pollen from anther to stigma, via wind, water, insects, or animals; can be self- or cross-pollination.

• Seed and Fruit Development: Ovule becomes a seed; ovary turns into a fruit, which protects and aids in seed dispersal.

• Germination: Seed absorbs water, activates growth, and the radicle (root) and shoot emerge, starting a new plant.

B. Asexual Reproduction in Plants (Vegetative Propagation)

• Produces offspring identical to the parent (clones).

• Common methods:

  • Runners (Stolons) – Horizontal stems (e.g., strawberry).

  • Rhizomes – Underground stems (e.g., ginger).

  • Tubers – Swollen underground stems (e.g., potato).

  • Bulbs – Modified leaves (e.g., onion).

2. Artificial Methods of Asexual Reproduction

Humans have developed artificial propagation techniques to grow plants efficiently.

• Cuttings – A stem, leaf, or root is cut and planted (e.g., roses, sugarcane).

• Grafting – A stem from one plant is attached to another (e.g., mango, apple).

• Budding – A bud is inserted into another plant (e.g., citrus trees).

• Micropropagation (Tissue Culture) – Plant cells are grown in a lab to create clones (used for orchids, bananas).

Artificial propagation helps in faster plant production, disease resistance, and preserving rare species.

II. REPRODUCTION IN ANIMALS

Animals reproduce through sexual and asexual reproduction.

A. Sexual Reproduction in Animals

• Involves the fusion of sperm (male gamete) and egg (female gamete) to form a zygote.

• Produces genetic variation in offspring.
  
  Types of Sexual Reproduction in Animals
  
  

• Gametogenesis: Formation of sperm and eggs through meiosis. (e.g., Humans, Frogs)

• Hermaphroditism: Organism has both male and female reproductive organs. (e.g., Earthworms, Clownfish)

• Fertilization: Fusion of sperm and egg to form a zygote. (External: Fish, Internal: Humans)

• Mating: Physical connection for sperm transfer. (e.g., Mammals, Fish)

1. Types of Fertilization

• External Fertilization

  • Sperm and egg unite outside the female body.

  • Common in aquatic animals (e.g., fish, amphibians).

  • Requires large numbers of gametes for successful fertilization.

• Internal Fertilization

  • Sperm is deposited inside the female reproductive tract.

  • Common in terrestrial animals (e.g., mammals, birds, reptiles).

  • Ensures a higher survival rate for offspring.

3. Modes of Reproduction Based on Embryo Development

• Oviparous (Egg-laying animals)

  • Embryo develops outside the mother’s body inside an egg.

  • Found in birds, reptiles, amphibians, insects, and fish.

• Ovoviviparous (Eggs hatch inside the mother’s body)

  • Embryo develops in an egg inside the female but is born live.

  • Found in sharks, rays, and some reptiles.

• Viviparous (Live-bearing animals)

  • Embryo develops inside the mother’s body and receives nutrients through the placenta.

  • Found in mammals (humans, dogs, cats, whales, etc.).

B. Asexual Reproduction in Animals

• Offspring produced without fertilization (identical to parent).

• Common in simple organisms like sponges, hydra, and starfish.

1. Types of Asexual Reproduction

• Budding – Small individual grows on parent (e.g., hydra, coral).

• Binary Fission – Parent splits into two equal parts (e.g., bacteria, amoeba).
  Types of Binary Fission - Irregular,Transverse, Longitudinal and oblique

• Fragmentation – Body breaks into pieces that develop into new individuals (e.g., starfish, flatworms).

• Parthenogenesis – Egg develops into an organism without fertilization (e.g., some insects, reptiles, fish).

• Regeneration – An organism can regenerate lost body parts, and in some cases, a whole new individual can grow from a part of the parent’s body.

• Drones, Workers, and Queens in Honeybees  – In honeybee colonies, a queen produces eggs that can develop into either queens, workers, or drones based on the diet and care they receive.