Selection & Speciation Flashcards
Causes of variation of phenotypes in sexual reproduction? (3)
- Mutation
- Meiosis
- Random fertilisation/ fusion of gametes
Graph of stabilising selection?
Graph of directional selection?
What is stabilising selection? (3)
- Selection pressure at both ends of distribution
- Favours the average + eliminates both extremes
- Reduces variability + evolutionary changes
What is directional selection? (2)
- Environmental change produces new selection pressure that favours an extreme
- Favour allele combination for survival
Graph of disruptive selection?
What is disruptive selection?
- Environment has selection pressures that favour 2 extreme phenotypes
What does Hardy-Weinberg predict? (6)
Allelic frequencies will remain constant from one generation to another as long as:
- Mating is random
- No mutations
- No migration
- No natural selection
- Large population
Definition of genetic drift?
Random change in allelic frequency within a small population
(e.g. natural disaster)
Definition of gene flow?
Change in allele frequency due to migration of fertile individuals
Definition of gene pool?
All the alleles of all the genes within a population
What is allopatric speciation? (2)
What is sympatric speciation? (2)
Types of reproductive isolation mechanisms? (6)
- Temporal - breed at different time of year
- Ecological - different habitats
- Behavioural
- Mechanical
- Gametic - incompatibility to prevent hybrid forming
- Hybrid - interbreed but offspring are infertile
(How does sympatric speciation occur?)
