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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.
The World's 100 most threatened species [1] is a compilation of the most threatened animals, plants, and fungi in the world. It was the result of a collaboration between over 8,000 scientists from the International Union for Conservation of Nature Species Survival Commission (IUCN SSC), along with the Zoological Society of London . [ 2 ]
A classic example of a population bottleneck is that of the northern elephant seal, whose population fell to about 30 in the 1890s. Although it now numbers in the hundreds of thousands, the potential for bottlenecks within colonies remains. Dominant bulls are able to mate with the largest number of females—sometimes as many as 100.
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).
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 Red List of 2012 was released 19 July 2012 at Rio+20 Earth Summit; [17] nearly 2,000 species were added, [18] with 4 species to the extinct list, 2 to the rediscovered list. [19] The IUCN assessed a total of 63,837 species which revealed 19,817 are threatened with extinction.
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
Polymorphism is the appearance of forms or "morphs" differing in color and number of attributes within a single species. [1]: 163 [2] In Lepidoptera, polymorphism can be seen not only between individuals in a population but also between the sexes as sexual dimorphism, between geographically separated populations in geographical polymorphism and ...