3. Natural Selection and Population genetics Flashcards
Metagenome
All genes available in a group of individuals
Macroevolution
Evolution over large taxonomic groups over a long period of time
- e.g. Archeopteryx to modern birds
Microevolution
Evolutionary changes within a population
Population Genetics
The study of genetic differences within and between populations
- Evolution acts on population
- Evolution = change in allele or gene frequency
Early belief on gene frequencies
Dominant alleles would take over recessive ones
Hardy - Weinberg Principle
Mathematically proved Mendelian inheritance
Limitation of Hardy-Weinberg Principle
Only for two alleles and simple dominant-recessive relationship
- Diploid
- Sexual reproduction only
- Generations are non-overlaping
- mating is random
- Population size is infinitely large
- Allele frequencies are equal in sexes
- No migration, mutation or selection
Population
Groups of organisms that share similar genes, that can exchange those genes
*Population in evolutionary theories = gene pool
Meta-population
All the individual isolated populations that are still capable of interbreeding but are reproductively isolated
- When put together can interbreed
Sub-population
sub-sample from a large population
Stratified populations
A single population that can interbreed but is starting to differ in gene frequencies in different parts of shared ranges
Unit of selection
The term/level we believe evolution is acting on
Unit of Selection in the Modern Synthesis
Genes
Natural Selection
The sum of all factors which cause differences in reproduction and survival among individuals in a population
Fitness
The extent to which a particular genotype contributes offspring to the next generation
Trait
A measurable and visible character in the phenotype of an organism
Discrete trait
A trait that consists of a smalle number of distinct alleles which do not vary along a continuous gradient
Continuous trait
Trait varies along a gradient
Fixed Trait
Determined genetically
- instinct
Plastic Trait
Influenced by environment
- learning
Stabilizing Selection
Extreme traits eliminated and the average stays
- Continuous or discrete
Disruptive Selection
Individuals with extreme variation have greater fitness
- Only continuous
Directional
Selection driven towards one genotype at the expense of others
- Continuous or discrete
Strength of Selection
Strong - Rapid evolution
- Low fitness will die or not reproduce
Weak - Slow evolution
- Low fitness has a disadvantage but still reproduces
Flight in birds - general
Usually stabilizing selection
Flight in birds - island
small wings
- strong wind makes harder to fly
- no predators
- less competitors
- directional selection
Convergent Evolution
Similar traits appear in vastly different species
- Not evolved from same trait
- e.g. blood
Trade-off
Selection of a trait in the cost of others
- Foundry cove worms - tolerance to Ni-Cd
- Dead with lower conc.
Gene-centered view of evolution
Gene is trying to survive
Organisms are only a vessel
