SEXUAL REPRODUCTION
The process by which the parent(s) produce another individual (offspring), usually of the same species, is known as reproduction. It is one of the characteristics that distinguishes a living creature. And by sexual, we mean reproduction in which two parents’ genetic material is combined in order to make offspring. When two haploid gametes combine, genetically unique diploid offspring are produced.
TYES OF SEXUAL REPRODUCTION
Allogamy
When the gametes that come together during fertilisation come from two distinct individuals, it’s called allogamy. The female gamete normally takes the shape of an egg or ovum, whereas the male gamete is a sperm. Both the egg and the sperm are cells that are specialised for reproduction; each sex cell has just 23 chromosomes (called haploid cells) rather than the regular 46 chromosomes found in other cells of the body. The two haploid cells combine to make a diploid cell, which then goes through mitosis to expand and form an individual creature. After the DNA has been replicated within the nucleus, mitosis is the division of one cell into two.
Internal Fertilization
Internal fertilisation is the fertilisation of an egg by sperm within one of the parents’ bodies, generally through sexual intercourse. After the male implants sperm, internal fertilisation takes place within the female body. There are a few exceptions, such as seahorses, where the female implants her eggs in the male and the zygote develops inside the male’s body.
The next step of internal fertilisation is dependent on the types of species. Birds, insects, and reptiles, for example, lay an egg containing the cells undergoing mitosis as well as a reserve of yolk to feed and sustain the embryo’s growth. A fully developed individual will emerge from the egg after a period of time (typically after being incubated). This is referred to as oviparity.
Most mammal embryos develop and mature within their mother’s body, resulting in the live delivery of a fully grown offspring: this is known as viviparity. The placenta supports embryos by providing food intake, waste disposal, and thermoregulation in placental creatures (most mammals).
External Fertilization
When a sperm cell and an egg cell combine outside of the body, it is called external fertilisation. External fertilisation is used by most amphibians and fish, as well as many invertebrates, to produce hundreds to billions of gametes at a time in close proximity. Spawning is defined as the rapid release of gametes into aquatic settings. Females will occasionally lay eggs on a specific substrate, which are then fertilised by males.
Externally fertilising species’ sex cells typically have particular adaptations for mobility, such as the inclusion of strong flagella for independent movement.
Autogamy
Autogamy is the fusion of male and female gametes produced by a single organism, often known as self-fertilisation or self-pollination. Hermaphrodites are species capable of producing both male and female gametes.
Although autogamy is similar to asexual reproduction in that it does not require a mate, the recombination of chromosomes between male and female gametes results in children with slightly changed genetic information, which might differ phenotypically from their parents. Autogamy is used by most plants and earthworms to reproduce. Hermaphrodites can breed with other hermaphrodites on rare occasions. In this instance, the population’s genetic diversity increases.
ASEXUAL REPRODUCTION
The process of reproducing without the use of sex cells or gametes is known as asexual reproduction. In contrary to sexual reproduction, asexual reproduction does not need the union of male and female gametes to produce offspring. The organism may reproduce in the absence of a mate, producing offspring that are frequently clones of the parent. Bacteria, archaea, a variety of plants, fungi, and certain mammals are examples of asexually reproducing organisms.
TYPES OF ASEXUAL REPRODUCTION
Fission
A parent splits into two or more offspring of almost equal size in fission (or binary fission). Single-celled creatures such as bacteria, archaea, and unicellular eukaryotes like protists and certain fungi use this kind of reproduction. When a single cell splits into two daughter cells, it is called a division.
Fragmentation
In fragmentation, a body breaks into many fragments, which eventually evolve into whole creatures. For example, A single ray, or arm, might evolve into a new starfish This method of reproduction is frequent in worms, fungi, and plants, in addition to starfish. Many of these species can reproduce sexually as well. Most lichens, which are formed when a fungus and photosynthetic algae or bacteria develop a symbiotic relationship, reproduce via fragmentation. This guarantees that both symbionts are present in new individuals.
Budding
Organisms reproduce by splitting off new individuals from existing ones, resulting in genetically identical parent and daughter organisms. The bud may remain linked to the parent or may break free. Budding occurs in eukaryotic species such as single-cell yeast and multicellular Hydra.
Vegetative Reproduction
Plants use vegetative reproduction, which is a sort of asexual reproduction. New individuals are created without the need of seeds or spores in this type of reproduction. The development of new plants from rhizomes or stolons, as in the strawberry plant, is an example of vegetative reproduction. Other plants reproduce by means of bulbs, tubers, shoots, and suckers that grow along lateral roots.
Agamogenesis
Any type of reproduction that does not include a male gamete is known as agamogenesis. Parthenogenesis and apomixis are two examples. Parthenogenesis is a type of asexual reproduction in which embryos grow and develop without being fertilised. Aphids, rotifers, nematodes, and other invertebrates, as well as numerous plants and reptiles like the Komodo dragon, naturally undergo parthenogenesis.
CONCLUSION
Living species have a variety of reproduction techniques, but the majority of them fall cleanly into one of two categories: sexual or asexual reproduction. Asexual reproduction produces genetically identical offspring from a single parent. Two parents contribute genetic information to make unique children during sexual reproduction.