Unit 2 - KA2.2 Evolution Flashcards
Define evolution
evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits
What are the three type of mutations?
Neutral
Positive
Negative
What type of mutations increase the individual’s fitness?
Positive
Changes in allele frequency during evolution take place through random and non-random processes. What are these?
Random - Genetic drift
Non-random - natural selection and sexual selection
What are the three causes of evolution?
Genetic Drift, Natural Selection, Sexual Selection
What is Natural Selection?
Non random process which affects the allele frequency in the population over generations
What is Sexual Selection?
non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring
Explain what a sexual dimorphism is?
sexual selection may lead to sexual dimorphism (where the different sexes have different physical characteristics)
What two factors cause sexual selection?
male-male rivalry and female choice
Define Genetic Drift
Random increase/decrease in the frequency of inherited traits over a number of generations
What are the two mechanisms of genetic drift
bottleneck and founder effect
What type of populations does genetic drift have the biggest effect?
Small populations
When do population bottlenecks occur?
population bottlenecks occur when a population size is reduced for at least one generation, due to disease, human impact, natural disasters etc.
When is the rate of evolution fast?
When selection pressures are strong
What is a selection pressure?
Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles.
Give some examples of selection pressures?
selection pressures can be biotic: competition, predation, disease, parasitism; or abiotic: changes in temperature, light, humidity, pH, salinity.
Describe what the Hardy-Weinberg principle states?
Hardy-Weinberg (HW) principle states that, in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations
One of the conditions for maintaining the Hardy-Weinberg principle is that there is no natural selection. What are the other conditions?
the conditions for maintaining the HW equilibrium as: no natural selection, random mating, no mutation, large population size and no gene flow (through migration, in or out)
What do the letters in the Hardy-Weinberg principle mean?
“p2 + 2pq + q2 = 1”
p = frequency of dominant allele
q = frequency of recessive allele
p2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q2 = frequency of homozygous recessive genotype
What does fitness mean in evolution?
fitness is an indication of an individual’s ability to be successful at surviving and reproducing
Define absolute fitness
absolute fitness is the ratio between the frequency of individuals of a particular genotype after selection, to those before selection
What is the absolute fitness equation?
(frequency of a particular genotype after selection )/(frequency of a particular genotype before selection )
Define relative fitness
relative fitness is 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
What is the relative fitness equation?
(number of surviving offspring per individual of a particular genotype)/(number of surviving offspring per individual of the most successful genotype)
Co-evolution is the process by which ____________________ evolve in response to __________________ imposed by each other.
co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other
What is symbiosis
symbiosis is a co-evolved intimate relationship between members of two different species.
Define mutualism?
mutualism occurs when 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 (+/+).
Define commensalism?
commensalism occurs when only one of the organism’s benefits (+/0).
Define parasitism?
parasitism takes place when the parasite benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources (+/-).
Explain what is meant by the red queen hypothesis?
the red queen hypothesis states that in a co-evolutionary relationship a change in the traits of one species can act as a selection pressure on the other species. This means that both species must evolve to survive.
