How Do Organisms Reproduce?

Notes

Chapter Overview Reproduction

Reproduction is the biological process through which organisms produce offspring of their own kind.

Importance Maintains continuity of species. Transfers hereditary characters. Produces variations. Helps evolution.

Important Board Line

Reproduction is essential for the survival of the species but not for the survival of an individual.

DNA Copying

During reproduction, DNA is copied.

DNA copying is never completely accurate.

This causes:

Small variations Diversity among organisms Better adaptation

Board Question Why are variations important?

Answer Variations help organisms survive changing environmental conditions and are the basis of evolution.

Types of Reproduction

1. Asexual Reproduction

Only one parent is involved.

No fusion of gametes.

Offspring are genetically identical (clones).

Characteristics One parent Fast process No fertilization Less variation Methods of Asexual Reproduction (A) Binary Fission

One organism divides into two.

Examples

Amoeba Paramecium

Diagram

Amoeba

O ↓ O O (B) Multiple Fission

One parent divides into many offspring.

Example

Plasmodium (C) Budding

A small bud develops on parent.

Examples

Hydra Yeast

Diagram

Hydra

| ( ) | ( ) (D) Fragmentation

Body breaks into fragments.

Each fragment forms a new organism.

Example

Spirogyra (E) Regeneration

Lost body parts regenerate into complete organisms.

Examples

Planaria Hydra (F) Spore Formation

Spores are produced inside sporangia.

Example

Rhizopus (Bread mould) (G) Vegetative Propagation

New plants develop from roots, stems or leaves.

Examples

Plant Vegetative Part Potato Stem Ginger Stem Onion Stem Bryophyllum Leaf Sweet Potato Root Advantages Faster reproduction Seedless plants produced Desired characters retained Sexual Reproduction

Two parents participate.

Fusion of male and female gametes forms a zygote.

Produces greater variation.

Sexual Reproduction in Flowering Plants Parts of Flower Male Part

Stamen

Anther Filament

Produces pollen grains.

Female Part

Pistil (Carpel)

Stigma Style Ovary Ovule Pollination

Transfer of pollen from anther to stigma.

Types Self Pollination

Same flower or same plant.

Cross Pollination

Different plants of same species.

Fertilization

Fusion of male and female gametes.

Produces

Zygote Embryo Seed Fruit Human Reproductive System Male Reproductive System

Main Parts