Evolution & Selection

(a) Evolution — the changes in organisms over generations as a result of genomic variations.
(b) Gene transfer. Vertical (inheritance) – from parent to offspring as a result of sexual or asexual reproduction. Prokaryotes can exchange genetic material horizontally, resulting in rapid evolutionary change. Prokaryotes and viruses can transfer sequences horizontally into the genomes of eukaryotes.
(c) Selection. Natural selection is the non-random increase in frequency of DNA sequences that increase survival. Sexual selection is the non-random increase in frequency of DNA sequences that increase reproduction. The differences in outcome as a result of stabilising, directional and disruptive selection.
(d) Genetic drift. The random increase and decrease in frequency of sequences, particularly in small populations, as a result of neutral mutations and founder effects.
(e) Speciation is the generation of new biological species by evolution as a result of isolation, mutation and selection.
The importance of geographical barriers in allopatric speciation. The importance of behavioural or ecological barriers in sympatric speciation. Hybrid zones.