Reproduction:
- Defined as a biological process in which an organism gives rise to young ones (offspring) similar to itself.
Reproduction is two types-
- Sexual reproduction
- Asexual reproduction
- When offspring is produced by a single parent without the involvement of gamete formation, the reproduction is called asexual reproduction
- When two parents ( opposite sex) participate in the reproduction process and also involve fusion of male and female gametes, it is called sexual reproduction
Asexual reproduction
In this method, a single individual (parent) is capable of producing offspring. As a result, the offspring that are produced are not only identical to one another but are also exact copies of their parent.
Methods of asexual reproduction:
- Binary fission
- Budding
- Fragmentation
- Parthenogenesis
Asexual reproduction
1. Budding:
an outgrowth or bud develops, grows, constricts at the base and separates from the parent body, e.g. yeast and Hydra. Unequal division of cytoplasm and parental identity is not lost.
2. Binary Fission
Binary fission – The body of an individual divides into two equal halves. Equal division of cytoplasm and parental identity is lost.It can be following types:
(a) Simple binary fission – When division occurs in any plane but it is always right angle to the elongated dividing nucleus,e.g. Amoeba.
(b) Longitudinal binary fission – When division occurs along the longitudinal axis, e.g. Euglena
(c) Transverse binary fission When division occurs along the transverse axis of the individual, e.g. Paramecium, diatoms.
d) Multiple fission The division of the parent body into many daughter organisms, e.g. Amoeba, Plasmodium, Monocystis (all Protozoa).
3. Spore Formation:
Members of the Kingdom Fungi and simple plants; like algae; reproduce by spore formation. Special asexual reproductive structures are formed in these organisms. Zoospores are the most common structure among such asexual reproductive structures. Zoospore is usually a microscopic motile structure. Other common asexual reproductive structures are conidia (Penicillium) and gemmules (sponge).
4. Fragmentation
Fragmentation occurs by breaking of the parent body into two or more parts, each of which grows to form an independent individual, e.g. algae like Spirogyra and bryophytes such as Marchantia, Riccia.
5. Regeneration
Regeneration is a type of asexual reproduction in which the missing part of the organism is repaired by the proliferation of cells, e.g. Hydra, Planaria and sponges.
6. Vegetative propagation
Vegetative propagation is the formation of a new plants from vegetative parts like root, stem, leaf, etc., naturally.