Evolutionary BiologyNatural Selection and Adaptation

Darwin’s observations:

- All species can produce more offspring than their environment can support and will not survive to reproduce

This suggest an unequal ability of individuals to survive and reproduce will lead to the accumulation of favourable traits in the population over time

- Members of the population often vary in their inherited traitsIndividuals whose traits give a higher probability of surviving and reproducing in an environment tend to leave more offspring than other individuals

Natural Selection:

Natural selection is a process by which individuals that have beneficial traits survive at a higher rate than those that don’t:- Populations evolve not individuals. Selection can diminish or amplify traits that differ between individuals in populations

Overtime selection can increase the match between organisms and their environment:- Environmental factors vary in space and time, traits that are favourable in place may not be in others

Environmental change or migration into new environments, natural selection may result in adaptation to these new conditions:- Could give rise to new species, selection continues and always happens

Homology:

Characteristics that share the same evolutionary origin but the function has changed

- Anatomy- Embryology- Genes and Proteins

Two types on homologous genes:

- Orthologous Genes - Paralogous Genes

Evolutionary control on the genes:

Mutations in genes

- Affects development and morphology

Population genetics: is the movement of alleles in populations

Alleles proliferate under positive selection

Alleles can be driven to extinction under purifying selection

Phylogenetic trees

Hypothesis of evolutionary relationships

Trees are constructed using characters A, T, G, C and amino acids

They are used to understand relationships between species, relationships between populations, epidemiology, population movements and speciation

Branches: Represents the evolutionary distance of a taxa from a common ancestor

Taxon: The organism

Taxa: A number of organisms

Node: Represents the most common ancestor between taxa

Clade: A number of closely related taxa

Polyphyletic Group

Some members have different ancestors

Monophyletic Group

A single common ancestor and all its descendants

Paraphyletic Group

Consists of an ancestral species and some but not all of the descendants

Phylogeography

Molecular relationships between populations

Provide ancestral and geographic history

Indicates population interactions with the environment and each other (predator/prey relationship)