4.4 Variance and evolution Flashcards
(32 cards)
What is the definition of variance?
Differences within a species
What are the characteristics of discontinuous variation?
Discrete grouping (e.g. blood type)
controlled by a single gene
What are the characteristics of continuous variation?
Continuous grouping
controlled by a number of genes (polygenetic)
influenced by environment
What is assumed when using the t-test?
Sample size is suitable
Sample is normally distributed
How does sexual reproduction produce genetic variation?
Independent assortment of chromosomes
crossing over during prophase 1
mixing of parental genotypes
What is a gene pool?
Total number of alleles for all genes in a population
What is genetic drift?
a change in allele frequencies in a population from generation to generation that occurs due to chance events
Why do genetic frequencies change?
Genetic drift
mutation
Natural selection (selection pressure)
What is selection pressure?
When an organisms environment determines the spread of alleles within a gene pool
What is the bottle neck effect?
reduced gene frequency caused by a natural disaster
What is the founder effect?
A few individuals from a population start their own population with varied allele frequency to the original population
What issues can arise with the founder effect?
Non representative group
Inbreeding causing health issues
What group is an example of the founder effect?
Pennsylvania Amish
What is an example of selection pressure?
MRSA
What are the similarities between bottlenecking and the founder effect?
followed by genetic drift
initial loss of biodiversity
small circle of breeding (inbreeding)
Untrue ratio of alleles to gen pop
What are the differences between bottlenecking and the founder effect?
Bottlenecking reduces choice of mates due to death whilst founders are geographically separated
What is allopatric speciation?
Different groups of the same species are geographically isolated
What is sympatric speciation?
reproductive barriers arising with in a population as a result of natural selection
What are isolation mechanisms?
Factors that prevent gene exchange between the population
What are some examples of isolation mechanisms?
Geographical features
habitat changes
behavioural changes
morphology changes
breeding mechanism changes
What are some examples of how sympatric speciation occurs?
morphological isolation (sex organ variation)
seasonal isolation (time of maturity)
Gametic isolation (gametes incompatible)
hybrid inevitability
hybrid sterility
What is hardy Weinberg’s assumption?
The frequency of alleles and genotypes will remain the same
What are the conditions of the Hardy Weinberg equation?
No natural selection
no mutation
No Migration
Random mating
Large population size
What is the Hardy Weinberg equation?
p^2 + 2pq + q^2 = 1
p + q = 1
