Unit 2: Organisms and Evolution, Evolution Flashcards
What is evolution?
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits.
What occurs during evolution?
During evolution, changes in allele frequency occur through the non-random processes of natural selection and sexual selection, and the random process of genetic drift
How does natural selection work?
Natural selection acts on genetic variation in populations
Variation in traits arises as a result of mutation. Mutation is the original source of new sequences of DNA. Most mutations are harmful or neutral but rarely they may be beneficial to the fitness of an individual.
What is sexual selection?
Sexual selection is the non random process by which individuals select alleles that increase the individuals chances of successfully mating and producing offspring.
What is genetic drift?
Genetic drift occurs when chance events
cause unpredictable fluctuations in allele
frequencies from one generation to the next
What is male - male rivalry?
Male-male rivalry: large size or weaponry
increases access to females through conflict.
This can cause sexual selection
What is female choice?
Female choice involves females assessing the fitness of males. This can cause sexual selection
p^2 + 2pq + q^2 = 1
What does each symbol mean?
Use the HW principle to calculate allele,
genotype and phenotype frequencies in
populations.
p^2 + 2pq + q^2 = 1
p = frequency of dominant allele
q = frequency of recessive allele
p^2 = frequency of homozygous dominant
genotype
2pq = frequency of heterozygous genotype
q^2 = frequency of homozygous recessive
genotype
What does the hardy Weinberg principle say?
The 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
What are the conditions required for the Hardy Weinberg principle to be possible?
The conditions for maintaining the HW equilibrium are: no natural selection, random mating, no mutation, large population size and no gene flow (through migration, in or
out).
What are selection pressures?
Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles.
What is fitness?
Fitness is an indication of an individual’s ability to be successful at surviving and reproducing
What is absolute fitness?
Absolute fitness is the ratio between the frequency of individuals of a particular genotype after selection, to those before selection.
What is 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 co evolution?
Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other
What are the three types of symbiotic relationships that can occur in co evolution?
Mutualism, parasitism and commensalism
What is mutualism
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 (+/+).
What is commensalism?
Commensalism: only one of the organisms benefits (+/0).
What is parasitism?
Parasitism: the parasite benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources (+/-).
What is the red queen hypothesis?
The Red Queen hypothesis states that, in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species
What is symbiosis?
Symbiosis: co-evolved intimate relationships between members of two different species.
