Lecture 6 Flashcards
Hybrid sterility examples
Liger (male lion female tiger)
Tigon (male tiger female lion)
Hinny (horse & donkey)
Mule (male donkey & female horse)
1st syllable is the male
Phylogenetics speices concept
species grouped together using phylogeny (evolutionary relatedness)
What is evolution (Darwin)
process driven by natural selection that changes populations of organisms over time, leading to speciation
What’s a Phenotype
- physical expression of a gene, i.e. behaviour, morphology or physiology
- influenced by both genes and the environment
What’s a genotype
set of genes an organism has
Phenotypic Plasticity
Variation we see in a phenotype due to environment
Heritability of a trait
h^2 = Vg / (Vg + Ve)
g = genome variation
e = environment variation
Index of heritability
0 (completely environmentally determined) to 1 (genetically determined)
Mechanisms of Evolution
Natural Selection and Genetic Drift
Natural Selection
- more offspring are produced than can survive
- traits vary and are heritable
- some heritable traits give an advantage
- advantageous traits provide higher fitness and becomes more common
Directional Selection
1 extreme phenotype becomes more favoured
What’s an adaptation
traits that have been selected for through natural selection
Stabilizing Selection
average phenotype (middle of a graph) is favoured (increases in frequency)
Disruptive selection
- 2 or more extreme phenotypes favoured
- average phenotype less frequent
Hardy-Weinberg Principle
- evolutionary forces are absent
- random mating
p^2 + 2pq + q^2 = 1
