Chapters

Reproduction

Reproduction is an integral feature of all living beings. The process by which a living being produces its own like is called reproduction.

Types of reproduction:

  1. Asexual Reproduction
  2. Sexual Reproduction

Asexual Reproduction

It is a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes, and almost never changes the number of chromosomes.

Sexual Reproduction

The production of new living organisms by combining genetic information from two individuals of different types (sexes). In most higher organisms, one sex (male) produces a small motile gamete which travels to fuse with a larger stationary gamete produced by the other (female)

Reproduction in simple organism

  1. Binary Fission
  2. Multiple Fission
  3. Budding
  4. Fragmentation
  5. Regeneration
  6. Spore Formation
  7. Vegetative reproduction

Binary Fission

The mother cell divides into two daughter cells; and each daughter cell begins its life like a new individual. The parent generation ceases to exist, after binary fission. Amoeba is a very good example of the organism which reproduces by binary fission.

Multiple Fission

When conditions become unfavourable, i.e. food, moisture, proper temperature, etc. are not available; this is the preferred mode of reproduction by unicellular organisms. A thick coating develops  are organism called cyst.  The nucleus divides into several nuclei and each daughter nucleus is surrounded by a membrane. All metabolic activities stop in the organism, after cyst formation. When favourable conditions return, the cyst dissolves or breaks down; releasing the daughter nuclei. 

Budding

Yeast typically grows asexually by budding. A small bud which will become the daughter cell is formed on the parent (mother) cell, and enlarges with continued grow. As the daughter cell grows, the mother cell duplicates and then segregates its DNA. The nucleus divides and migrates into the daughter cell.

Fragmentation

It is seen in filamentous algae. In this a single parent breaks into parts that regenerate into whole new individuals.

Regeneration

Some simple organisms can regenerate a new individual from a part which has been accidentally cut off.

Spore Formation

Most of the fungi, bryophytes and pteridophytes reproduce by this method. Spores are produced in special spore-bearing organs; called sporangium. When spores mature; the sporangium bursts open to release them.

Vegetative reproduction

Only one plant is involved and the offspring is the result of one parent. The new plant is genetically identical to the parent. New plants grow from parts of the parent plant. They include: Stems, roots, leaves, grafting, layering etc.


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