Evolution Flashcards
What is evolution?
the change over time in the proportion of individuals in a population differing in one or more inherited traits
What is sexual selection?
the non-random process involving the selection of alleles that increase the individuals chances of mating and producing offspring
Sexual selection may lead to
sexual dimorphism
Sexual selection can be due to
male-male rivalry and female choice
When does genetic drift occur?
when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
Why is genetic drift more important in small populations
alleles are more likely to be lost from the gene pool
Why is a gene pool altered by genetic drift?
because certain alleles may be under-represented or over-represented and allele frequencies change
When can the rate of evolution be rapid?
When selection pressures are strong
What does the Hardy-Weinberg (HW) principle state?
In the absence of evolutionary influence, allele and genotype frequencies in a population will remain constant over the generations
What can the HW principle be used to determine?
Whether a change in allele frequency is occurring to a population over time. Changes suggest evolution is occurring
What is male-male rivalry?
large size or weaponry increases access to females through conflict
What does female choice involve?
females assessing the fitness of males
When do population bottlenecks occur?
When a population size is reduced for at least one generation
How do founder effects occur?
Through the isolation of a few members of a population from a larger population
The gene pool of the new population is not ______________ of that in the original gene pool
(founder effects)
representative
(founder effects)
What are selection pressures?
the environmental factors that influence which individuals in a population pass on their alleles.
What are the conditions for maintaining the HW equillibrium?
no natural selection, random mating, no mutation, large population size, no gene flow
What is the Hardy-Weinberg formula?
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 is fitness?
Fitness is an indication of an individuals ability to be successful at surviving and reproducing
Absolute fitness formula
frequency of a particular genotype after selection/frequency of a particular genotype before selection
Fitness is a measure of
the tendency of some organisms to produce more surviving offspring than competing members of the same species
If the absolute fitness is 1, then
the frequency of that genotype is stable
If the value for absolute fitness is greater than 1 it conveys
an increase in the genotype
If the value for absolute fitness is less than 1 it conveys
a decrease in the genotype
Relative fitness formula
number of surviving offspring per individual of a particular genotype/number of surviving offspring per individual of the most successful genotype
What is co-evolution?
The process by which two or more species evolve in response to selection pressures imposed by each other.
Co-evolution is frequently seen in pairs of species that have
symbiotic interactions
The Red Queen hypothesis states that
A change in the traits of one species acts as a selection pressure on the other species. This means that species in these relationships must adapt to avoid extinction
What is symbiosis?
a co-evolved intimate relationship between members of two different species
Mutualism
both organisms in the interaction are interdependent on each other for resources or other services. Both organisms gain from the relationship (+/+)
Commensalism
only one of the organisms benefits (+/0)
Parasitism
the parasite benefits in terms of energy or nutrients and the host is harmed (+/-)
