Definition of Sexual Reproduction
Sexual reproduction is the process in which new organisms are created, by combining the genetic information from two individuals of different sexes. The genetic information is carried on chromosomes within the nucleus of specialised sex cells called gametes. In males, these gametes are called sperm and in females the gametes are called eggs. During sexual reproduction the two gametes join together in a fusion process known as fertilisation, to create a zygote, which is the precursor to an embryo offspring, taking half of its DNA from each of its parents. In humans, a zygote contains 46 chromosomes: 23 from its mother and 23 from its father. The combination of these chromosomes produces an offspring that is similar to both its mother and father but is not identical to either.
Sexual reproduction differs from asexual reproduction, which only requires one parent. In asexual reproduction, unlike sexual reproduction, there is no fusion of gametes, so the offspring are genetically identical to their parents and are therefore clones. Asexual reproduction does occur in some animals, although it is rare; most asexual reproduction occurs in bacteria, fungi, starfish, corals, hydras (jellyfish) and some flowering plants such as strawberries.
Types of Sexual Reproduction
Allogamy
Allogamy occurs when the gametes which join together during fertilisation come from two different individuals. The female gamete is usually in the form of an egg or ovum while the male gamete takes the form of a sperm. Both egg and sperm are cells specialised to perform the task of reproduction; each sex cell contains only 23 chromosomes (these are called haploid cells) rather than the normal 46 chromosomes present in other cells of the body. The two haploid cells fuse together to create a diploid cell which then undergoes mitosis, in order to grow and form an individual organism. Mitosis is the division of one cell into two, after the DNA has been replicated within the nucleus.
Internal Fertilisation
Internal fertilisation is the fertilisation of the egg by the sperm within the body of one of the parents, usually by means of sexual intercourse. Internal fertilization usually takes place within the female body, after the male implants sperm. However there are exceptionally rare examples, such as seahorses (Sygnathidae), where the female implants her eggs into the male and the zygote is formed within the male’s body.
External Fertilisation
External fertilisation occurs when a sperm cell and an egg cell join outside of the body. Most amphibians and fish and many invertebrates use external fertilisation, producing anything from hundreds to billions of gametes at a time into close proximity. The quick release of gametes into aquatic environments is called spawning. However, sometimes females will lay eggs on a particular substrate which are subsequently fertilised by males.
Autogamy
Autogamy, also known as self-fertilisation or self-pollination, is the fusion of male and female gametes, which are produced by a single individual. Species which are able to produce both male and female gametes are called hermaphrodites.
Advantages of Sexual Reproduction
Deleterious mutations accumulate within DNA over time, through cell mitosis. Organisms which produce asexually simply pass these mutations on to their offspring, while organisms which combine their DNA through sexual reproduction allow only a portion of their deleterious mutations to pass to their offspring, increasing their chances of survival. This effect is increased through natural selection, where individuals with exceptionally harmful mutations are unable to pass on their genes through sexual reproduction.
Increased diversity of genes within a population also allows natural selection to improve an organism’s ability to adapt to environmental changes. Random mutations, which are of no use to one generation, may become key to survival in future generations under a change of environmental pressures. This is the driving force behind.
List of the Disadvantages of Sexual Reproduction.
- It takes time and energy to find a mate and reproduce.
To reproduce sexually, the two genders must find each other. Finding a suitable partner with the desired traits takes time and effort in order for the kids produced by the union to thrive. For certain species, mating is an all-consuming task that necessitates entire concentration on the reproductive cycle until it is accomplished.
- Reproduction through sexual means is uncertain.
Sexual reproduction is not a 100% effective means of producing children. Some of your chosen partners might be infertile. Others, despite multiple tries to have kids, may not have the gametes come together. Although this method of reproduction has a variety of advantages, it is a risky procedure.
- Favorable genetics might not be passed to the offspring.
The genetics of two parents are combined in the offspring of two parents. With sexual reproduction, inheritance patterns are prevalent. Autosomal dominant and recessive, x-linked dominant and recessive, and mitochondrial patterns are all possible.
- Fewer offspring are typically produced.
Multiple offspring can be produced by sexual reproduction at the same time. Humans normally have one kid, but twins, triplets, and bigger multiples are possible. Horses usually only have one foal every litter, although cats and dogs can have up to a dozen.
- It can be deadly.
The purpose of sexual reproduction is to have an orgasm, yet success might come at a cost. A brain aneurysm affects up to 5% of the population, and the process of sexual reproduction can cause the aneurysm to rupture.
CONCLUSION:
In conclusion, sexual reproduction brings about many advantages such as genetic variation, recombination function to eliminate mutations, also increase resistance to parasites and producing organisms different to each other.