Lesson 2: Natural selection Flashcards
(16 cards)
What causes variation in a population?
Mutation, meiosis (crossing over + independent assortment), and random fertilisation.
Where must a mutation occur to affect natural selection?
In a gamete (sperm or egg), so it can be passed to offspring.
What is overproduction of offspring?
Species produce more offspring than the environment can support, leading to competition for resources.
What are selection pressures?
Environmental factors that influence which individuals survive and reproduce.
What is stabilising selection?
Selection that favours the average phenotype and removes extremes.
What is directional selection?
Selection that favours one extreme phenotype.
What is disruptive selection?
Selection that favours both extremes, but not the average.
What is sexual selection?
A form of natural selection where individuals with certain traits are more likely to attract mates and reproduce.
What are the assumptions of Hardy-Weinberg equilibrium?
No mutations
No natural selection
No migration
Random mating
Large population size
What is the Hardy-Weinberg principle?
A model that predicts allele frequencies in a non-evolving population will remain constant.
What is the Hardy-Weinberg equation for allele frequencies?
p+q=1
(one is dominant and the other is recessive allele)
What is the Hardy-Weinberg equation for genotype frequencies?
p^2 + 2pq + q^2 = 1
What is genetic drift?
Random changes in allele frequencies in a population
What is the bottleneck effect?
When a population is drastically reduced causing a loss of genetic diversity.
What is the founder effect?
When a few individuals colonise a new area, leading to reduced genetic variation in the new population.
Define gene pool.
The total set of all alleles present in a population at a given time.
