Reproduction Definition

“Reproduction is the process of producing offspring that are biologically or genetically similar to the parent organism.”

Types of Reproduction

There is a large diversity in the biological world. Each organism has evolved its own mechanism to multiply and produce offsprings. Both external (habitat) as well as internal (physiology) factors are collectively responsible for how it reproduces. Broadly speaking there are two types of reproduction, asexual and sexual.

Asexual Reproduction

It is a mode of reproduction/multiplication in which new individuals develop from a single parent.

Features of asexual reproduction:

1. As there is involvement of only one parent so it is uniparental.
2. It can occur with or without gamete formation but gametic fusion is absent.
3. The individuals produced are exact copies of each other and their parents because the new organisms produced inherit all of its chromosomes from one parent. Moreover, it involves only mitotic division Such a group of morphologically and genetically similar individuals is called clone.
4. It can occur through unspecialised or specialised parts of parent.
5. It is widespread among different groups of organisms. It is common method of reproduction in organisms that have a relatively simple organisation like single celled organisms belonging to group monera, protist as well as plants and animals with relatively simple organisation like algae, fungi, sponges.
6. Though it is a common mode of reproduction in lower organisms, but it should be very much clear that higher plants also exhibit this type of reproduction where it is known as vegetative reproduction.
7. Simple and quick method of reproduction.

Let us discuss different ways of asexual reproduction

1. Binary Fission: In this process, the parent organism divides into two halves, each half forming an independent daughter organism, e.g., Amoeba.
2. Budding: The bud grows, constricts at the base and separates. So, bud remains attached initially to the parent cells which eventually separates and mature into new organism (cell). e.g., Yeast
3. Sporulation:  A new organism grows from the spores. These can be created without fertilization and can spread through wind and animals. e.g., Chlamydomonas
4. Fragmentation: Fragmentation is a form of asexual reproduction where an organsm splts into fragments. Each of these fragments develops into mature fully grown individual followed by mitosis. It occurs in some algae (Spirogyra), fungi, Hydra, etc.
5. Vegetative Reproduction/Propagation: It is a method of multiplication in which a somatic part of the plant detaches from the mother’s body and develops into a new Independent plant under suitable environmental conditions is called vegetative reproduction.

Sexual Reproduction

Sexual reproduction involves formation and fusion of gametes to form the zygote which develops to form a new organism.

Characteristics

1. Two fusing gametes can be produced by same individual or different individuals. So it can be both uniparental as well as biparental (mostly).
2. Offsprings produced are not identical to parents or amongst themselves because organisms produce inherits chromosome/genetic material contributed from two different gametes. So we can say it produces variations.
3. It involves meiosis and syngamy (fusion of gametes)
4. It is a slow, elaborate or complex process, so multiplication is not so rapid.

Events in Sexual Reproduction

1. Pre-fertilization Events

These are events in sexual reproduction which occur prior to the process of fertillzation. The two main prefertilization events are gametogenesis and gamete transfer.

2. Fertilisation

The most vital event of sexual reproduction is the fusion of gametes. This process is called syngamy or fertilisation which results in the formation of a diploid zygote.

3. Post-Fertilisation Events

Events in sexual reproduction after the formation of zygote are called post-fertilisation events.