process of reproduction in sexual reproduction?
Answers
Explanation:
=>the production of new living organisms by combining genetic information from two individuals of different types (sexes). In most higher organisms, one sex (male) produces a small motile gamete which travels to fuse with a larger stationary gamete produced by the other (female).
There are two main processes during sexual reproduction: meiosis, involving the halving of the number of chromosomes, and fertilization, involving the fusion of two gametes and the restoration of the original number of chromosomes
Sexual reproduction was an early evolutionary innovation after the appearance of eukaryotic cells. During sexual reproduction, the genetic material of two individuals is combined to produce genetically-diverse offspring that differ from their parents. The fact that most eukaryotes reproduce sexually is evidence of its evolutionary success. In many animals, it is actually the only mode of reproduction. The genetic diversity of sexually-produced offspring is thought to give species a better chance of surviving in an unpredictable or changing environment.
Scientists recognize some real disadvantages to sexual reproduction. On the surface, creating offspring that are genetic clones of the parent appears to be a better system. If the parent organism is successfully occupying a habitat, offspring with the same traits would be similarly successful. Species that reproduce sexually must maintain two different types of individuals, males and females, which can limit the ability to colonize new habitats as both sexes must be present. Therefore, there is an obvious benefit to an organism that can produce offspring whenever circumstances are favorable by asexual budding, fragmentation, or asexual eggs. These methods of asexual reproduction do not require another organism of the opposite sex. Indeed, some organisms that lead a solitary lifestyle have retained the ability to reproduce asexually. In addition, in asexual populations, every individual is capable of reproduction. In sexual populations, the males are not producing the offspring themselves. In theory, an asexual population could grow twice as fast.
Nevertheless, multicellular organisms that exclusively depend on asexual reproduction are exceedingly rare. Why is sexuality (and meiosis ) so common? This is one of the important unanswered questions in biology and has been the focus of much research beginning in the latter half of the twentieth century. There are several possible explanations, one of which is that the variation that sexual reproduction creates among offspring is very important to the survival and reproduction of the population. Thus, on average, a sexually-reproducing population will leave more descendants than an otherwise similar asexually-reproducing population. The only source of variation in asexual organisms is mutation. This is the ultimate source of variation in sexual organisms, but, in addition, those different mutations are continually reshuffled from one generation to the next when different parents combine their unique genomes and the genes are mixed into different combinations by the process of meiosis. Meiosis is the division of the contents of the nucleus, dividing the chromosomes among gametes.
The process of meiosis produces unique reproductive cells called gametes, which have half the number of chromosomes as the parent cell. Fertilization, the fusion of haploid gametes from two individuals, restores the diploid condition. Thus, sexually-reproducing organisms alternate between haploid and diploid stages. However, the ways in which reproductive cells are produced and the timing between meiosis and fertilization vary greatly. There are three main categories of sexual life cycles: diploid-dominant, demonstrated by most animals; haploid-dominant, demonstrated by all fungi and some algae; and the alternation of generations, demonstrated by plants and some algae.