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
during evolution how do the changes in allele frequency occur
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
what does natural selection act on
Natural selection acts on genetic variation in populations
how does variation arise
Variation in traits arises as a result of mutation.
what is the result of selection
Selection results in the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles.
what does population produce
Populations produce more offspring than the environment can support
what are individuals with variations that are better for the environment tend to do
Individuals with variations that are better suited to their environment tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation
what is sexual selection
Sexual selection is the non-random process involving the selection of alleles that increase the individual’s chances of mating and
producing offspring
what may sexual selection lead to
Sexual selection may lead to sexual dimorphism
what may sexual selection be due to
Sexual selection can be due to male-male rivalry and female choice
what is male-male rivalry
Male-male rivalry: large size or weaponry increases access to females through conflict.
when does genetic drift occur
Genetic drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
in what type of population is genetic drift more important in
Genetic drift is more important in small populations, as alleles are more likely to be lost from the gene pool
when do population bottlenecks occur
Population bottlenecks occur when a population size is reduced for at least one generation.
how do founder effects occur
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 representative of that in the original gene pool.
what is a gene pool altered by
A gene pool is altered by genetic drift because certain alleles may be underrepresented or over-represented and allele frequencies change
what happens when rapid selection pressures are strong
Where selection pressures are strong, the rate of evolution can be rapid
what are selection pressures
Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles.
what can selection pressures be
They can be biotic: competition, predation, disease, parasitism; or abiotic: changes in temperature, light, humidity, pH, salinity.
what does the hw principle state
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 can the Hardy- Weinberg principle be used to determine
The HW principle can be used to determine whether a change in allele frequency is occurring in a population over time
what do changes suggest
Changes suggest evolution is occurring
Define fitness
Fitness is an indication of an individual’s ability to be successful at surviving and reproducing
what is fitness
Fitness is a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species
how can fitness be defined
Fitness can be defined in absolute or relative terms
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 do each of the letters represent in the Hardy-Weinberg theory
p squared+ 2pq +q squared = 2 1
p = frequency of dominant allele
q = frequency of recessive allele
p squared = frequency of homozygous dominant
genotype
2pq = frequency of heterozygous genotype
q squared = frequency of homozygous recessive
genotype
what is the hw principle used to calculate
Use the HW principle to calculate allele, genotype and phenotype frequencies in populations.
what happens if the absolute fitness is 1
If the absolute fitness is 1, then the frequency of that genotype is stable. A value greater than 1 conveys an increase in the genotype and a value less than 1 conveys a decrease.
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 does a change in the traits of one species acts as
A change in the traits of one species acts as a selection pressure on the other species
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
This means that species in these relationships must adapt to avoid extinction
what is co - evolution frequently seen in
Co-evolution is frequently seen in pairs of species that have symbiotic interactions
The impacts of these relationships can be positive (+), negative (-) or neutral (0) for the individuals involved Mutualism, commensalism, and
define symbiosis
Symbiosis: co-evolved intimate relationships between members of two different species.
define commensalism
Commensalism: only one of the organisms benefits (+/0).
define 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 (+/+).
define 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 are most mutations
Most mutations are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.
What are mutations the original source of
Mutation is the original source of new sequences of DNA. These new sequences can be novel alleles.
What does female choice involve
Female choice involves females assessing the fitness of males.
