population and evolution Flashcards
Gene pool
all alleles of all genes of all individuals in a species
allellic frequency
the number of times an allele appears in a population
wardy weinburg
is a maths equation that shows allele frequency of a specific gene
what does the hardy Weinburg equation assume?
no mutation occur no migration occurs no selection large population random mating isolated population
variation in phenotype
differences in physical characteristics caused by genetic and environmental reasons
mutations
These sudden changes to genes and chromosomes
may, or may not, be passed on to the next generation. Mutations are a main source of variation.
meiosis
random segregation
crossing over of alleles
fertilisation
random
environment factors for variation in phenotype
Environmental influences include
climatic conditions (e.g., temperature. rainfall. and sunlight), soil
conditions, pH. and food availability.
continuous features are shown in
normal curves
The environmental factors that limit the population of a species are called
selection pressures
the process that affects selections
organisms produce more offspring than can be supported by the
the available supply of food, light, space, etc.
• there is a genetic variation within the populations of all species.
• a variety of phenotypes that selection operates against.
overpopulation
increases intraspecific competition
individuals best fitted outcompete and produces
stabilising selection
preserves the average phenotype (phenotypes
around the mean) of a population by favouring average individuals,
selection against the extreme phenotypes
directional selection
changes the phenotypes of a population by
favouring phenotypes that vary in one direction from the mean of the population.
selection for one extreme phenotype
disruptive selection
favours individuals with extreme phenotypes
rather than those with phenotypes around the mean of the population.
what affects allele frequency
selection
speciation
the process where a new species develops from an existing species that have a common ancestor that could reproduce to have fertile young
speciation process
one or more populations of a species become separated
different mutations will occur in a population
populations have different selections pressures
natural selection-
leads to different allelic frequency
genetic drift
this happens in small populations where genetic variation is small
as there is a small number of alleles there is not an equal ratio for them to be passed on.
