It is the process by which an individual multiplies in number by producing more individuals of its own type.
Basic Features of Reproduction include :
- Synthesis of RNA and proteins
- Replication of DNA
- Cell division
- Formation of reproductive units or bodies
- Development of reproductive units into young ones.
Types of Reproduction
I. Asexual Reproduction
Asexual Reproduction is the process of multiplication of individuals without the formation or fusion of gametes.
It involves a single parent and the young ones produced through it are genetically similar to the parent.
Asexual reproduction occurs in several ways :
It involves the division of the nucleus followed by that of the cytoplasm, breaking the body into two young ones.
It occurs in unicellular organisms, e.g., Amoeba, Euglena, Paramecium, etc.
2. Multiple Fission
In this the nucleus divides into several daughter nuclei, followed by the simultaneous division of the cytoplasm.
The nuclei move towards the periphery and each one is surrounded by small amount of cytoplasm which gives rise to new daughter cells.
It occurs in protozoa e.g., Plasmodium.
In many protozoa and bacteria the asexual reproduction occurs by the division of nucleus into several daughter nuclei, and then each daughter nucleus gets enclosed by small amount of cytoplasm to form a spore.
Budding is an unequal division of the parent where the identity of the parent body is still maintained.
It is in contrast to binary fission where parent body divides equally into two and no identity of the parent is left.
Bud is an outgrowth formed on the surface of the body which finally gets detached and develops into a young one.
It is common in Hydra.
The body may break into two or more fragments, and each fragment develops into a complete individual e.g., Filamentous algae, Spirogyra.
II. Sexual Reproduction
The process of sexual reproduction involves the formation and fusion of gametes (Syngamy) and results in the formation of a new organism genetically different from parent.
Sexual reproduction is usually biparental, i.e., involves a male and a female individual producing a male and a female gamete respectively.
Such animals are called unisexual or dioecious e.g., frog, cockroach, humans.
In certain animals, the male and female sex organs are present in the same individual.
Such species are called monoecious or bisexual. e.g., earthworm, leech.
Parthenogenesis is a specialized reproduction in which eggs develop without fertilization e.g., bees, ants, wasps, etc.
Mammalian Reproductive System
The reproductive system of sexually reproducing animals consists of :
- Primary Sex Organs (called gonads) which produce gametes and hormones.
- Secondary Sex Organs / Glands which participate in reproduction but do not form gametes.
- Accessory Sex Organs / Characters which distinguish the two sexes in appearance.
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