Chapter 18 - Populations and evolution Flashcards
What is the gene pool?
All the allele of all the genes of a population
What is allelic frequency?
The number of times an allele occurs within the gene pool
What will the allelic frequency always be?
Less than one
What does the Hardy-Weinberg principle predict?
The frequency of alleles will stay constant over generations providing there are no mutations
What are the five conditions required for the Hardy-Weinberg principle to work?
No mutations Population is isolated - no new alleles No selection Large population Mating is random
What does p equal?
Dominant allele
What does q equal?
Recessive allele
What are the two Hardy-Weinberg equations?
p + q = 1
p^2 + q^2 + 2pq = 1
What are the three ways in which variation occurs?
Mutations, meiosis, random fertilisation of gametes
How does meiosis produce variation?
Nuclear division produces new combinations of alleles
What does stabilising selection do?
Preserves the average phenotype by reducing the variation of values around the mode
What does directional selection do?
Favours an extreme phenotype
What does disruptive selection do?
Favours both extreme phenotypes
How does directional selection occur?
Natural selection
What may disruptive selection result in?
Speciation