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Evolution
The change over time in the proportion of individuals in a population differing in one or more inherited traits
Changes in allele frequency
Caused by the non-random processes of natural selection and sexual selection, and the random process of genetic drift
Mutations
The original source of new sequences of DNA. These new sequences can be novel alleles. Most are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.
Selection
Results in the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles. Can be natural or sexual.
Sexual selection
The non-random process involving the selection of alleles that increase the individual's chances of mating and producing offspring. May lead to sexual dimorphism
Male-male rivalry
Large size or weaponry increases access to females through conflict.
Female choice
Involves assessing the fitness of males
Genetic drift
Chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. More important in small populations
Population Bottleneck
This occurs when a population size is reduced for at least one generation.
Founder effect
This occurs through the isolation of a few members of a population from a larger population. The gene pool of the new population is not representative of that in the original gene pool.
Selection pressures
Environmental factors that influence which individuals in a population pass on their alleles. They can be biotic: competition, predation, disease, parasitism; or abiotic: changes in temperature, light, humidity, pH, salinity.
The Hardy-Weinberg (HW) principle
In the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations.
Conditions for the HW equilibrium
No natural selection, random mating, no mutation, large population size and no gene flow (through migration, in or out)
Hardy-Weinberg equation
p^2 + 2pq + q^2 = 1
Fitness
An indication of an individual's ability to be successful at surviving and reproducing
Absolute fitness
The ratio between the frequency of individuals of a particular genotype after selection, to those before selection
Relative fitness
The ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype
Co-evolution
The process by which two or more species evolve in response to selection pressures imposed by each other. A change in the traits of one species acts as a selection pressure on the other species
Mutualism
Both organisms in the interaction are interdependent on each other for resources or other services. As both organisms gain from the relationship, the interaction is (+/+).
Commensalism
Only one of the organisms in a symbiotic relationship benefits (+/0).
Parasitism
One organism benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources (+/-).
The Red Queen Hypothesis
In a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species. This means that species in these relationships must adapt to avoid extinction
