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[3]: 126 The most common example is sexual dimorphism, which occurs in many organisms. Other examples are mimetic forms of butterflies (see mimicry), and human hemoglobin and blood types. According to the theory of evolution, polymorphism results from evolutionary processes, as does any aspect of a species.
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.
An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that has major differences from the ancestral group's condition, and is thus not considered part of the ancestral group, while still having enough similarities that we can group them under the same clade.
This example of acoustic aggressive mimicry is similar to the Photuris firefly case in that the predator's mimicry is remarkably versatile – playback experiments show that C. leucoviridis is able to attract males of many cicada species, including Cicadettine cicadas from other continents, even though cicada mating signals are species-specific ...
Polymorphic and/or mimetic females occur in the case of some taxa in the Papilionidae primarily to obtain a level of protection not available to the male of their species. The most distinct case of sexual dimorphism is that of adult females of many Psychidae species who have only vestigial wings, legs, and mouthparts as compared to the adult ...
If the basis for selection is at an individual level, altruism makes no sense at all. But universal selection at the group level (for the good of the species, not the individual) fails to pass the test of the mathematics of game theory and is certainly not the general case in nature. [30] Yet in many social animals, altruistic behaviour exists.
An example could be when a species becomes reproductively isolated on an island, as in peripatric speciation. fugitive species A species that only temporarily occupies environments or habitats (either because its members frequently migrate or because its environments frequently change) and so does not persist for many generations at any one ...
Agonistic behaviour is a result of evolution, [5] and this can be studied in a number of species facing different environmental pressures. Though agonistic behaviours can be directly observed and studied in a laboratory setting, it is also important to understand these behaviours in a natural setting to fully comprehend how they have evolved and therefore differ under different selective ...