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The Ka/Ks ratio test compares the number of non-synonymous to synonymous substitutions, and a ratio that is greater than 1 indicates directional selection. [12] The relative ratio test looks at the accumulation of advantageous traits against a neutral model, but needs a phylogenetic tree for comparison.
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).
In the evolutionary biology of sexual reproduction, operational sex ratio (OSR) is the ratio of sexually competing males that are ready to mate to sexually competing females that are ready to mate, [1] [2] [3] or alternatively the local ratio of fertilizable females to sexually active males at any given time. [4]
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.
In mathematics, two sequences of numbers, often experimental data, are proportional or directly proportional if their corresponding elements have a constant ratio. The ratio is called coefficient of proportionality (or proportionality constant) and its reciprocal is known as constant of normalization (or normalizing constant).
Sexual selection creates colourful differences between sexes in Goldie's bird-of-paradise.Male above; female below. Painting by John Gerrard Keulemans.. Sexual selection is a mechanism of evolution in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ...
is the average number of people infected from one other person. For example, Ebola has an of two, so on average, a person who has Ebola will pass it on to two other people.. In epidemiology, the basic reproduction number, or basic reproductive number (sometimes called basic reproduction ratio or basic reproductive rate), denoted (pronounced R nought or R zero), [1] of an infection is the ...