Origins of Biodiversity Summary of Evolution There is variance between individuals of a population These variations are due to inherited genes Some variations are better suited for success than others Resources are limited leading to competition There will be winners and losers Over time changes will accumulate in a population Natural Selection Those more adapted thrive and reproduce while others don’t live long enough to have offspring Speciation Over time, if a population becomes separated from others and isolated, the differences may increase so much that, should the populations be reunited they will be unable to interbreed Isolation is key!!!!

Physical Isolation (Geographic) Large Flightless Birds Only occur on continents that were once part of Gondwana (Africa, Australia/NZ, South America) But since it broke apart so long ago they have greatly diverged Australia Separated from Gondwana long ago Placental mammals outcompeted marsupials on South America and Africa On Australia the opposite happened East Africa’s Rift Valley Lakes New Lakes form throughout rifting Creates a founder effect and adaptive radiation

Land Bridges Allow species to invade new areas North and South America joined by volcanics Some land bridges form temporarily by lowering sea levels and or ice ages

Plate Tectonics Continents drift into different climate zones This greatly affects the fitness of many species Plate Tectonics also builds mountain ranges etc which create new habitats/niches

Geologic Timescale Earth is about 4.6 billion years old Life shows up in fossil record about 4 billion years ago 65 million years ago the dinosaurs went extinct Humans have been recognizable for about 200,000 years If geologic time was a 24 hour day humans would have appeared in the last few seconds