Gene pools and speciation

Nature of science:

Looking for patterns, trends and discrepancies—patterns of chromosome number in some genera can be explained by speciation due to polyploidy. (3.1)

• 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.

Applications and skills:

• Application: Identifying examples of directional, stabilizing and disruptive selection.
• Application: Speciation in the genus Allium by polyploidy.
• Skill: Comparison of allele frequencies of geographically isolated populations.

Guidance:

• Punctuated equilibrium implies long periods without appreciable change and short periods of rapid evolution.

• 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