Mutations: CCG ACT A A G TAC CG G CCG ACT A G G TAC CG T Genetic Variation The Fuel The Raw Materials Production Order: Organisms Adapted to Cambrian Selective Pressures: The fuel for natural selection is genomic variation that enables evolutionary adaption to proceed. Without fuel, the machine stops, at least until replenished by the accumulation of new mutations. Chemicals in land, sea and air

Cambrian Explosion Timeframe Begins at base of Cambrian period of Paleozoic Era, some 540 million years ago Fossil Record suggests: Evolutionary adaptation increases ~ 10 fold All but one of the extant animal phyla appeared over ~ 20 million years, less than.5% of Earth’s geologic time Other phyla appeared but did not survive (e.g., Vetulicolia) The so called explosion abruptly terminated at about 515 million years ago, after which a biodiversity decline ensued

Gene Flow Offspring of immigrated has genotype Hh Gene flow is the transfer of alleles from one population to another population through immigration of individuals. In this example, one of the birds from population A (blue) immigrates to population B (red), which has less of the dominant alleles, and through mating incorporates its alleles into the other population. Population A: blue Population B: red

Phylum Vetulicola