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In 1973, M. J. D. White, then at the end of a long career investigating karyotypes, gave an interesting summary of the distribution of chromosome polymorphism. "It is extremely difficult to get an adequate idea as to what fraction of the species of eukaryote organisms actually are polymorphic for structural rearrangements of the chromosomes.
In biology, polymorphism [1] is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (one with random mating).
It operates on polymorphic species, species which have different forms. In apostatic selection, the common forms of a species are preyed on more than the rarer forms, giving the rare forms a selective advantage in the population. [1] It has also been discussed that apostatic selection acts to stabilize prey polymorphisms.
This condition has been detected in many species. Trichomycterus davisi, for example, is an extreme case where the polymorphism was present within a single chimeric individual. [1] It has also been studied in alfalfa, [2] shrews, [3] Brazilian rodents, [4] and an enormous variety of other animals and plants. [5] In one instance it has been ...
The extreme case of genetic polymorphism is that of the papilionid great Mormon (Papilio memnon), where four male forms and many as twenty-six female forms are reported. This species, and others in its genus, have been extensively studied for understanding the genetic basis for polymorphism and Batesian mimicry. [3] [4] [5]
Endangered species by reason(s) they are (or were) threatened — the cause(s) for species being endangered in their native habitats.; This is primarily a sub-category for IUCN Red List species by the external threat(s) stated in IUCN reports for each listed species (hyperlinked under 'References' &/or 'External links' on most wikipedia articles when species are on IUCN Red List).
The good news for the milkvetch plant is that they usually need wildfire to sprout — meaning dormant seeds now have a massive new habitat for a new crop of the rare shrub.
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs .