10.3 Gene pools and speciation

Essential idea:
Gene pools change over time.
Understandings:	Nature of science:
A gene pool consists of all the genes and their different alleles, present in an interbreeding population. Evolution requires that allele frequencies change with time in populations. Reproductive isolation of populations can be temporal, behavioural or geographic. Speciation due to divergence of isolated populations can be gradual. Speciation can occur abruptly.	Looking for patterns, trends and discrepancies—patterns of chromosome number in some genera can be explained by speciation due to polyploidy. (3.1)
Applications :	Guidance:
Identifying examples of directional, stabilizing and disruptive selection. Speciation in the genus Allium by polyploidy.	Punctuated equilibrium implies long periods without appreciable change and short periods of rapid evolution.
Skill:
Comparison of allele frequencies of geographically isolated populations.	Punctuated equilibrium was long considered an alternative theory of evolution and a challenge to the long established paradigm of Darwinian gradualism. How do paradigm shifts proceed in science and what factors are involved in their success? Utilization: Many crop species have been created to be polyploid. Polyploidy increases allelic diversity and permits novel phenotypes to be generated. It also leads to hybrid vigour. Syllabus and cross-curricular links: Biology Topic 5.1 Evidence for evolution

License