BIOA01H3 Lecture 10: Lecture 10

• School: UTSC
• Department: Biological Sciences
• Course: BIOA01H3
• Professor: Maydianne Andrade

Document Summary

Genetic isolation: allopatric speciation: physical barrier divides a population (no gene flow) Founder effects can cause initial stages of divergence. Mutation can give rise to different alleles in groups. Selection and drift can lead to independent changes in allele frequencies in groups. Reef fishes (wrasse) in caribbean sea and pacific ocean: formation of isthmus of panama 3 mya = vicariance event for marine. Varieties on nearby islands but different sub/species: e. g. Caribbean anolis lizards: sympatric speciation: subgroups form within a population occupying the same geographic region. Specialization or genetic changes in subgroups reduce gene flow: Dispersal to new islands followed by local adaptive radiation. Host races: different variants favour distinct hosts: e. g. Some prefer hawthorn fruit while others prefer apples both are equally good hosts. Polyploidy: more than 2 pairs of homologous chromosomes: may form 2 new species: Autopolyploidy: spontaneous non-disjunction of chromosomes at meiosis, result is gametes with doubled chromosomes.