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Direct reciprocity was proposed by Robert Trivers as a mechanism for the evolution of cooperation. [1] If there are repeated encounters between the same two players in an evolutionary game in which each of them can choose either to "cooperate" or "defect", then a strategy of mutual cooperation may be favoured even if it pays each player, in the short term, to defect when the other cooperates.
The McDonald–Kreitman test [1] is a statistical test often used by evolutionary and population biologists to detect and measure the amount of adaptive evolution within a species by determining whether adaptive evolution has occurred, and the proportion of substitutions that resulted from positive selection (also known as directional selection).
Therefore, parents allot equal investment of effort in both sexes. More generally, the expected sex ratio is the ratio of the allotted investment between the sexes, and is sometimes referred to as Fisherian sex ratios. However, there are many examples of organisms that do not demonstrate the expected 1:1 ratio or the equivalent investment ratio.
The Trivers–Willard hypothesis has been applied to resource differences among individuals in a society as well as to resource differences among societies.Investigations in humans pose a number of practical and methodological difficulties, [6] but while a 2007 review of previous research found that empirical evidence for the hypothesis was mixed, the author noted that it received greater ...
These are direct phenotypic benefits, sensory bias, the Fisherian runaway hypothesis, indicator traits and genetic compatibility. In the majority of systems where mate choice exists, one sex tends to be competitive with their same-sex members [ 4 ] and the other sex is choosy (meaning they are selective when it comes to picking individuals to ...
Harvard evolutionary biologist Ernst Mayr (1961) [8] suggested that there are two fundamentally different types of causation in biology, ‘ultimate’ and ‘proximate’. Ultimate causes (e.g. natural selection ) were seen as (i) providing historical accounts for the existence of an organism's features, and (ii) explaining the function or ...
The tertiary sex ratio is equivalent to the adult sex ratio (ASR), which is defined as the ratio of adult males to females in a population. [ 6 ] [ 7 ] The operational sex ratio (OSR) is the ratio of sexually active males to females in a population, and is therefore derived from a subset of the individuals included when calculating the ASR. [ 7 ]
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...