Natural Selection & Change over time

Charles Darwin British naturalist Sailed on the HMS Beagle around the world Collected and recorded all the different species and fossils he came across Wanted to explain biodiversity

Darwin at the Galapagos The Galapagos islands have many different biomes – Hot and dry like the desert – Rainy and full of plants Within each biome, Darwin would find different species that were suited to live there

Darwin at the Galapagos Noticed that several organisms had differences depending on where they lived

Darwin’s Finches Uses beak to crush seeds Uses twigs to probes insects in trees Probes in holds in trees for insects Uses beak to grasp insects

Darwin’s Observations Organisms tend to over produce Variation exists within a population

Darwin’s Conclusion Darwin summarized his conclusions in The Origin of Species – Common Descent with Modification – Evolution by Natural Selection

Back to the giraffe Ancestors of giraffes had slight variations The ones with slightly longer necks survived longer and reproduced more The ones with shorter necks eventually died out

Artificial Selection

Evidence The fossil record

Evidence Biogeography

Evidence Homologous body structures Vestigial organs

Evidence Embryology

Molecular Homologies

Theory of the origin of life

Early Earth Earth is about 4.6 billion years old Lots of lightning Early atmosphere was full of poisonous gases, water vapor, and no oxygen

Habitable Earth About 3.8 billion years ago, Earth cooled enough for water to remain liquid

Theory of the origin of life Miller & Urey (1950s) Simulated early Earth’s atmosphere Added a spark of electricity to simulate lightning They made… AMINO ACIDS!

4 Step process for the origin of life

The First Eukaryotes About 2 million years ago, eukaryotes evolved (endosymbiosis)