10.3 Gene Pools and Speciation

Gene Pool

A gene pool represents the sum total of alleles for all genes present in a sexually reproducing population

Change in Allele Frequency

• Mutation

• Gene Flow

• Sexual Reproduction

• Genetic Drift

• Natural Selection

Population Bottleneck

Occur when an event reduces a population massively(~50%)

Types of Selection

• Stabilising → Intermediate phenotype is favoured at the expense of phenotypic extremes, e.g. human birth weight

• Directional → One phenotypic extreme is favoured at the expense of the other phenotypic extreme, e.g. development of AMR in bacteria

• Disruptive → Both phenotypic extremes are favoured at the expense of intermediate phenotypes, bimodal spread, e.g. seasonal changes, e.g. black or white moths

Types of Isolation

• Temporal Isolation

• Behavioural Isolation

• Geographic Isolation

• Reproductive Isolation

Types of Speciation

• Allopatric Speciation → geographical barrier

• Sympatric Speciation → any other kind of isolation

Pace of Speciation

• Phyletic Gradualism → smooth and continuous process, cumulative small changes

• Punctuated Equilibrium → species remain stable for long periods with abrupt rapid changes