2.2 Organisms and Evolution: Evolution Flashcards
2.2 (26 cards)
what is evolution?
the change over time in the proportion of individuals in a population differing in one or more inherited traits
change in allele frequency can occur as a result of three processes, what are these?
genetic drift
natural selection
sexual selection
what are the non-random processes that cause a change in allele frequency?
natural selection
sexual selection
what are the random processes that cause a change in allele frequency?
genetic drift
where is genetic drift more significant?
because alleles are more likely to be lost from the gene pool
What does natural selection act on in populations?
genetic variation
(These variations help individuals survive and reproduce better, passing on beneficial traits.)
why does selection occur?
Because populations produce more offspring than the environment can support.
why do individuals with variations that are better suited to their environment tend to survive longer and produce more offspring?
they breed to pass on the alleles that conferred an advantage to the next generation
what is sexual selection?
the non-random process involving the selection of alleles that increase the individuals chances of mating and producing offspring
what is the main source of new alleles arising in a population?
mutation
what can sexual selection lead to?
sexual dimorphism, where males can develop slightly different traits to females
what is genetic drift?
random change in how frequently a particular allele occurs within a population
what is the Hardy-Weinberg principle?
in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations
what does a change in allele frequency suggest?
that evolution is occurring
what is meant by fitness?
an indication of an individuals ability to be successful at surviving and reproducing, it refers to all the contributions made to a gene pool of the next generation by individual genotypes.
how can fitness be measured?
absolute and relative terms
what is absolute fitness?
the ratio between the frequency of individuals of a particular genotype
after selection, to those before selection
what is 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?
A change in the traits of one species acts as a selection pressure on the other species
what is symbiosis?
an interrelationship between two organisms of different species whereby at least one species benefits
what is mutualism?
a symbiotic relationship where both species benefit (+/+)
what is commensalism?
a symbiotic relationship where only one of the organism benefits from the relationship and the neither benefits nor suffers (+/0)
what is parasitism?
a symbiotic relationship where one species benefits from the relationship at the expense of the host (+/-)
what is the Red Queen’s Hypothesis?
in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species
