2.2 evolution Flashcards
what are three types of symbiotic interactions?
mutualism (+/+), commensalism (+/0), parasitism (+/-)
in what kind of interaction does co-evolution usually occur?
A symbiotic interaction
in co-evolution, how does a change in the traits of one species affect the other species?
it acts as a selection pressure
what is co-evolution?
change in the genetic composition of one species (or group) in response to a genetic change in the other
how is relative fitness calculated?
number of surviving offspring per individual of a particular genotype/number of surviving offspring per individual of the most successful genotype
what is relative fitness?
the ratio of surviving offspring of one genotype compared with the most successful genotype
what does an absolute fitness of 1 mean?
the number of individuals of that genotype is stable
what does an absolute fitness of <1 mean?
there is a decrease in individuals of that genotype
what does >1 mean?
there is an increase in individuals of that genotype
what is absolute fitness?
the ratio that compares the frequency of a particular genotype from one generation to the next
what is fitness?
a term used to measure an individual’s ability to be successful at surviving and reproducing, and refers to the genetic contribution made to the next generation
what does q2 represent?
frequency of homozygous recessive genotype
what dos 2pq represent?
frequency of heterozygous genotype
what does p2 represent?
frequency of homozygous dominant genotype
what does q represent?
frequency of recessive allele
what does p represent?
frequency of dominant allele
what is the equation used to calculate allele, genotype and phenotype frequencies in a population?
p2 + 2pq + q2 = 1
what can the HW principle be used to determine?
whether a change in allele frequency is occurring in a population over time
what does the Hardy-Weinberg principle state?
in the absence of evolutionary influences, allele and gene frequencies in a population will remain constant over generations
name some abiotic selection pressures
- change of temperature
- light
- himidity
- pH and salinity
name some biotic selection pressures
- competition<div>
- predation</div><div>
- disease</div><div>
- parasitism</div>
<p>what are selection pressures?</p>
the environmental factors that influence which individuals in a population pass on their alleles
what can cause the rate of evolution to be rapid?
when selection pressures are high
how does natural selection affect the population?
non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles.
how does sexual selection affect the population?
inbreeding or selection of mates for specific phenotypes will reduce heterozygosity.
how do mutations affect the population?
increases or decreases allele frequencies, and may introduce new alleleforms
what is gene flow?
movement of alleles due to immigration and emigration of individuals between populations
what are some male rivalry strategies to gain access to females?
- acquiring and defending territories and harems
- direct conflict
- superior size and weaponry
- alpha male approach
which aspects of a male play a role in female choice and why?
male resources, appearance and courtship as it shows the levels of male fitness
what does sexual selection refer to?
it is females who retain primary control over reproduction
how do behavioural sex differences affect the organism?
they can decrease its chance of survival as it is more visible to predators, but allow for greater success in mating
what are common examples of behavioural sex differences?
- pronounced coloration<div>
- increased size</div><div>
- striking adomments</div><div>
- elaborate courtship behaviours</div>
what is the clearest sexual dimorphism amongst vertebrates?
gamete size
describe the process of natural selection
- populations produce more offspring than the environment can support
- individuals with variations that are better suited to the environment survive longer and reproduce more
- meaning that favourable alleles are passed on to future generations
how do founder effects alter a gene pool?
certain alleles may be under/over-represented, causing allele frequencies to change
what are founder effects caused by?
the isolation of a few members of a population that are not representative of the original gene pool
when do bottleneck effects occur?
when a population size is reduced for at least one generation
how can genetic drift reduce genetic diversity?
it causes the random loss of rare alleles
what kind of population does genetic drift have a greater impact on and why?
small, isolated populations - alleles are more likely to be lost from the gene pool
what is genetic drift caused by?
chance events or unpredictable fluctuations
what is genetic drift?
the random change in how frequently a particular allele occurs within a population
what is a non-random process in evolution?
natural selection, sexual selection
what is a random process in evolution?
genetic drift
what is evolution?
the change over time in the proportion of individuals in a population differing in character traits
