UNIT 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 does natural selection act on?
natural selection acts on genetic variation in different populations
what is variation caused by?
mutations
what is the source of new DNA sequences?
mutation is the original source of new sequences of DNA, these sequences can be novel alleles
what is natural selection?
the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles
what processes cause changes in alleles?
the non-random processes of natural selection, sexual selection and the random process of genetic drift
are mutations beneficial?
most mutations are deleterious or neutral but in rare cases they may be advantageous to the fitness of an individual
what is the issue with current populations?
populations produce more offspring than the environment can handle
what does selection result in?
selection results in the non-random increase in the frequency of advantageous alleles and the non-random decrease in frequencies of deleterious alleles
what is sexual selection?
the non-random process involving the selection of alleles that increase the individuals chance of mating and producing offspring
what can sexual selection lead to?
sexual dimorphism - sexual selection may lead to differences in form between male and female individuals
what is sexual selection due to?
male-male rivalry and female choice
what is female choice?
females assessing the fitness of males
how does genetic drift occur?
genetic drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
when is genetic drift most important?
genetic drift is most important in smaller populations as alleles are more likely to be lost from the gene pool
what is the bottleneck effect?
the bottleneck is a genetic rift that can occur when a population size is reduced for generation
what is a founder effect?
founder effects are examples of genetic rift that can occur through the isolation of a few members from the larger population and the gene pool of the new population is not representative of the larger population
how is a gene pool altered by genetic drift?
a gene pool is altered by genetic drift because certain alleles may be under represented or over represented and so allele frequencies change
what are selection pressures?
they are the environmental factors that influence which individuals in a population pass on their allele
what is meant by abiotic selection?
temperature, light, humidity, pH, salinity
what is meant by biotic selection?
competition, predation, disease, parasitism
what happens when selection pressures are strong?
the rate of evolution can be rapid
what does the Hardy Weinberg principle state?
It 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 of maintaining the Hardy Weinberg principle?
random mating, no natural selection, no mutation, large population size and no gene flow due to migration
what is the Hardy Weinberg equation used to determine?
it is used to determine whether a change in allele frequency is occurring in a population over time, if it is then this would suggest that evolutionary processes are occurring
what is the Hardy Weinberg equation?
p^2+2pq+q^2=1
p^2 = frequency of dominant homozygous genotype q^2 = frequency of recessive homozygous genotype 2pq = frequency of heterozygous genotyppe
what is fitness an indication of?
fitness is the indication of an individuals ability to be successful at survival and reproducing
what is fitness a measure of?
fitness is a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species
what is absolute fitness?
it is the ratio between the frequency of a genotype in individuals after selection, to those before selection
what does it mean if absolute fitness is 1?
this means that the frequency of that genotype is stable. a value greater than 1 means an increase in the genotype and less means a decrease
what is relative offspring?
this is the ratio of surviving offspring per individual with the most successful genotype
what does co-evolution mean?
this is the process by which two or more species evolve in response to selection pressures imposed by each other.
what can a change in traits act as?
a change in traits of one species acts as a selection pressure on the other
where is coevolution usually seen?
in pairs of species that have symbiotic interactions
symbiosis meaning?
a coevolved intimate relationship between members of two different species
what type of effect does a symbiotic relationship have?
the effects of this can be both negative and positive or neutral for the species involved
what is mutualism?
mutualism is a symbiosis where species in the interaction rely on each other for resources or other services and since both species gain the interaction is positive for both parties
what is commensalism?
is a symbiosis in which only one of the species substantially benefits from and for the other species the relationship is usually neutral
what is parasitism?
is a sybiosis in which the parasite species benefits in terms of energy or nutrients while the host is harmed by the loss of nutrients
what is the the red queen hypothesis?
states that in a coevolutionary relationship, change in the traits of one species can act as selection pressure on the other species which must adapt to avoid extinction
what is sexual dimorphism?
females are generally inconspicuous; males usually have more conspicuous markings, structures and behaviours
what factors can cause a genetic drift?
disease
abiotic factors
isolation
natural disasters
what is intrasexual?
selection within the same sex
what is intersexual?
selection between individuals of different sexes
what are the stages of coevolution?
1) individuals of species A has a trait that gives them an advantage over species b
2) proportion of individuals with the treat in species A increases
3) some individuals within species B now have a trait that gives them an advantage
4) proportion of individuals with said trait in population b increases
steps of natural selection?
1) too much offspring for the environment to sustain
2) individuals struggle for survival until reproductive age
3) better-adapted individuals survive, reproduce and pass on their favoured alleles
4) less well adapted individuals die and dont pass on their genes
what is 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
what are the equations for absolute and relative fitness?
AF -
(New generation/Previous generation)
Frequency of a particular genotype after selection/Frequency of a particular genotype before selection
RF - (AF of the genotype/AF of most successful genotype)
The frequency of surviving offspring per individual of a particular genotype/The frequency of surviving offspring per individual of the most successful genotype
