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Encyclopedia > Reproductive isolation

An important concept in evolutionary biology, reproductive isolation is a category of mechanisms that prevent two or more populations from exchanging genes. The separation of the gene pools of populations, under some conditions, can lead to the genesis of distinct species. Reproductive isolation can occur either by preventing fertilization, or by the creation of a degenerate or sterile hybrid, such as the case with the common mule and the hinny. The gene pool of a species or a population is the complete set of unique alleles that would be found by inspecting the genetic material of every living member of that species or population. ... In biology, a species is one of the basic units of biodiversity. ... Categories: Biology stubs ... In biology, hybrid has three meanings. ... In its common modern meaning, a mule is the offspring of a male donkey and a female horse. ... A hinny is the offspring of a male horse and a female donkey (jennet or jenny). ...


Fertilization Barriers (pre-zygotic)

Pre-zygotic barriers to fertilization include everything from a physical barrier (such as an ocean) formed between two populations to errors in cell division that cause incompatibility between populations.


Speciation by repANISHAAAAroductive isolation is frequently seen in plants, with errors in division during mitosis doubling the number of chromosomes and thereby preventing even pairing of chromosomes with normal gametes during fertilization. For various species that bloom seasonally, the time of gamete release can prevent hybridization, a temporal isolation. For animal species, mating might be stymied. Incompatible genitalia forms a mechanical reproductive isolation, and members of opposite sexes often fail to recognize one another, due to some morphological difference used to identify a potential mate. Speciation refers to the evolutionary process by which new biological species arise. ... Light micrograph of a newt kidney cell in early anaphase of mitosis. ... Figure 1: Chromosome. ... Gametes, from the ancient Greek γαμετης (spouse), are the specialized germ cells that come together during fertilization (conception) in organisms that reproduce sexually. ... Blossom is a term given to the flowers of stone fruit trees (Genus Prunus) and of some other plants with a similar appearance that flower profusely but for a short period of time. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis...


The gametes of different species are frequently incompatible, and do not form a viable zygote. SpermTANNNA may not possess the proper enzymes for penetrating the coat of the ovum, or have the proper chemical markers to signal the egg cell to accept it. This article or section does not cite its references or sources. ... A human ovum An ovum (from Latin, loosely, egg or egg cell) is a female sex cell or gamete. ...


Hybrid Barriers (post-zygotic)

If fertilization does occur, several other barriers for the hybrid exist. The first is, in animals, spontaneous abortion of the hybrid fetus. For a hybrid that has been born, there is a considerable chance that the hybrid will be sterile and produce no offspring of its own, isolating its genes from both parental groups. Hybrids can be unfit, and die before developing into sexual maturity and passing on their genes. Finally, hybrids that do produce offspring can, potentially, produce sterile progeny. These mechanisms prevent the recycling of genetic material in distinct species. Fetus at eight weeks Foetus redirects here. ... Fitness (often denoted in population genetics models) is a central concept in evolutionary theory. ...

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