1. 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!!!!

2. 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

3. 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

4. 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

5. 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