2.3: Agents of Evolutionary Change - Natural Selection

macroevolution

evolutionary changes among taxonomic groups above species level. includes origin diversification and extinction across long periods of time. Revealed through changes in fossil record and transitions across phylogeny of life

microevolution

evolution within species that can be observed directly acting upon natural pops. can be influenced by agents of change

when do adaptive mutations occur

when phenotype and function match = favoured by natural selection = variant increases in pop over generations

adaptation

refers to favoured trait - advantageous mutations contribute to a trait that is adaptive

natural selection

a process where organisms better adapted to environment tend to survive and reproduce more successfully than others. - it can act on advantageous and deleterious mutations

 Is all natural selection adaptive?

No. can be

• Adaptive (pos) = increases advantageous traits.

• Purifying (neg) = removes harmful traits.

• Balancing selection = maintains multiple variants in a population.

Only positive selection directly drives adaptation.