Populations & Evolution (Topic 7B) Flashcards
the Hardy-Weinberg principle states that…
the frequencies of alleles in a population remains constant over time
the five conditions that have to be met for the Hardy-Weinberg principle are:
- no mutations
- no immigration
- no selection
- mating is random
- population is large
frequency of 1 allele will always be ___ than _ and will be expressed as a _____
less
1
decimal
give the equations associated with the hardy weinberg principle
p + q = 1
p^2 + 2pq + q^2 = 1
what does p stand for in the hardy-weinberg principle?
dominant
what does p^2 stand for in the hardy-weinberg principle?
homozygous dominant
what does q^2 stand for in the hardy-weinberg principle?
homozygous recessive
what does q stand for in the hardy-weinberg principle?
recessive
the three types of natural selection are….
stabilising selection
directional selection
disruptive selection
directional selection works against ___ of the _____ in a range of ____
one
extremes
phenotypes
directional selection results in…
one phenotype becoming rare and another becoming common
stabilising selection works against ___ _____ in a range of ____
both extremes
phenotypes
stabilising selection results in…
range about the phenotype decreases
what are the 6 steps of natural selection?
- within a population, there are random mutations, which can lead to an advantageous phenotype, which make an individual more likely to survive.
- they reproduce and pass on the gene.
- A greater proportion of the next Generation have it
- They in turn on more likely to survive and pass on their genes
- The frequency of the allele increase every generation
- This leads to evolution as the allele becomes more common
name the 3 types of adaptions..
behavioural
physiological
anatomical
when does stabilising selection occur?
in a constant environment
what does stabilising selection reduce?
the range of possible phenotypes
disruptive selection occurs when…
the environment favours more than one phenotype
what is speciation?
the formation of a new species from pre-existing species over time, as a results of changes to gene pools from generation to generation
a group of the same species can be living in the same place place but in order for speciation…
there must exist two populations within that group and no gene flow occurs between them
in sympatric speciation two things split or separate the population they are…
- ecological separation
- behavioural separation
sympatric speciation can be caused by ecological separation. what is ecological separation?
populations are separated because they live in different environments within the same area
give an example of ecological separation
soil pH can differ greatly in different areas which has a major effect on plant growth
sympatric speciation can be caused by behavioural separation. what is behavioural separation?
populations are separated because they have different behaviours
give an example of behavioural separation…
differences in feeding, communication or social behaviour
allopatric selection occurs as a result of…
geographical isolation
what is the most common type of speciation?
allopatric
in allopatric speciation if is there is sufficient selection pressure or genetic drift acting to change the gene pools then…
the populations will diverge and form separate species
what is geographical isolation?
a species population splits into one or more groups that then become separated by geographical barriers
geographical isolation creates…
two populations of the same species but no genetic exchange can occur between them
