Evolution Flashcards
What does population genetics investigate?
how allele frequencies within a population change over time
What is the gene pool of a population?
the sum of all genes in a population at any given time
What is allele frequency?
frequency of a particular allele in a population
not linked to whether its dom or rec- changes over time due to changing conditions
What doe the hardy-weinberg principle state
in a stable, non-evolving population, the allele frequency will remain constant
what is the hardy-weinberg principle used to calculate?
the proportion of people or number of individuals with a specific genotype based on monogenetic inheritance
What assumptions does the hardy-weinberg principle make?
large populations
random mating
no mutations
no selection pressure= no evolution happening
making the principle unrealistic to apply in a majority of cases
What are the 2 equations expressed in the hardy-weinberg principle?
no of dom alleles + no of recessive alleles = 1 = total
p + q = 1
What factors affect evolution?
lead to changes in allele frequency= affect rate of evolution
mutations- necessary for existence of diff alleles in first place, formation of new alleles= genetic diversity
sexual selection= increase in alleles that code for characteristics for mating success
gene flow- movement of alleles between populations- immigration and emigration
genetic drift- occurs in small populations, change in allele frequency due to random nature of mutations. Appearance of new allele= greater affect and is more likely to increase in a smaller population, as there is less alleles present in gene pool
natural selection- increase in alleles that code for beneficial characteristics, allowing organisms with these characteristics to survive
What is the impact of small populations?
smaller gene pool = less alleles = less genetic diversity = greater affected by new predators, climate change or human behaviour, less able to adapt over time
What are limiting factors?
factors which limit or decrease the size of a population
density-dependant factors- dependant on population size- competition, predation,, communicable disease
density-independent factors- affect populations of all sizes in the same way- climate change, natural disaster, seasonal change, human activities
What are genetic bottlenecks, and what is their affect?
large reduction in population size, lasting for at least one generation
gene pool and genetic diversity is greatly reduced,
effects seen in future generations
takes thousands of years for genetic diversity to redevelop through slow accumulation of mutations
What is a positive aspect of a genetic bottleneck?
beneficial mutation = greater impact
lead to quicker development of a new species
thought to have played role in early development of humans
What is the founder effect?
small populations arise through establishment of new colonies by a few isolated individuals
extreme example of genetic drift
smaller gene pool = less genetic variation
rare characteristic carried to new population = become more frequent
EG- Armish people from America
What is a normal distribution?
distribution of diff variations will take the form of a bell-shaped curve
What is stabilising selection?
the norms are selected for, and the extremes selected against
EG- birth weight of babies
average weight= form peak of graph = most common
light babies = prone to infection
heavy babies = difficult births
both extremes reduce survival chances = low survival rates of heavy and light babies
average weight babies are more likely to survive and reproduce = natural selection and survival of the fittest
Diagrams of selection types
