Definition of Reproduction

• The process by which mature individuals produce offspring is called reproduction.
• Reproduction is a characteristic of all living organisms and prevents extinction of a species.
• There are two types of reproduction: sexual and asexual reproduction.

Asexual Reproduction

• Asexual reproduction is the formation of offspring from a single parent.
• The offspring are identical to the parent.
• Asexual reproduction does not involve gametes.

Types of asexual reproduction.

1. Binary fission in amoeba
2. Spore formation in Rhizopus
3. Budding in yeast

1. Binary Fission

• This involves the division of the parent organism into two daughter cells.
• The nucleus first divides into two and then the cytoplasm separates into two portions.
• Binary fission also occurs in bacteria, Paramecium, Trypanosoma and Euglena.

2. Spore Formation in Rhizopus

• Rhizopus is a saprophytic fungus which grows on various substrate such as bread, rotting fruits or other decaying organic matter.
• The vegetative body is called mycelium which has many branched threads called hyphae.
• Horizontal hyphae are called stolons.
• Vertical hyphae are called sporangiophore.
• The tips of sporangiophore become swollen to form sporangia, the spore bearing structure.
• Each sporangium contains many spores.
• As it matures and ripens, it turns black in colour.
• When fully mature the sporangium wall burst and release spores which are dispersed by wind or insects.
• When spores land on moist substratum, they germinate and grow into a new Rhizopus and start another generation.

Spore Formation in ferns

• The fern plant is called a sporophyte.
• On the lower side of the mature leaves are sari (Singular: sorus) which bear spores.

3. Budding in Yeast

• Budding involves the formation of a protrusion called a bud from the body of the organism.
• The bud separates from the parent cell, in yeast budding goes on so fast and the first bud starts to form another bud before the separation.
• A short chain or mass of cells is formed.

Advantages of Asexual Reproduction

• Good qualities from parents are retained in the offspring without variation.
• New individuals produced asexually mature faster.
• Process does not depend on external factors which may fail such as pollination.
• New individuals obtain nourishment from parent and so are able to survive temporarily under unsuitable conditions.
• No indiscriminate spreading of individuals which can result in wastage of offspring.
• Takes a shorter time and leads to rapid colonization.

Disadvantages of asexual reproduction

• New offspring may carry undesirable qualities from parents.
• Offspring may be unable to withstand changing environmental conditions.
• Faster maturity can cause overcrowding and stiff competition.
• Reduced strength and vigour of successive generations.

Sexual Reproduction

- Sexual reproduction involves the fusion of male and female gametes to form a zygote.
- The fusion of the male gamete and the female gamete is known as fertilization.
- Human beings reproduce through sexual reproduction.
- Animals and most plants also reproduce through sexual reproduction.
- In animals, the female gamete is known as egg cell and the male gamete is known as sperm cell

Advantages of sexual reproduction

• Leads to variations.
• Variations which are desirable often show hybrid vigour.
• High adaptability of individuals to changing environmental conditions.
• Variations provide a basis for evolutionary changes.

Disadvantages of sexual reproduction

• Fusion is difficult if two individuals are isolated.
• Some variations may have undesirable qualities.
• Population growth is slow.