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How Do We Know that Earth is Ancient?
- Stratigraphy
- Fossil record
- Radiometric dating Radioactive isotope and half-life Multiple Methods Used to Date Strata How Has Earth Changed over Time? - Unidirectional changes: gradual cooling, weakening continental drift forces. - O 2 accumulated after prokaryotes evolved ability to split water. - How long before O 2 levels were high enough to support multicellular life? Prokaryotes - ancestors of bacteria were the first life 1 st^ eukaryotes depended on free O 2
Eukaryotes - compartmentation and complexity How Has Earth Changed over Time?
- Evolution, mass extinctions affected by…
- Rapid climate change, continental drift, volcanism, and major shifts in sea levels.
- External events, such as meteorite collisions. Climate shifts affect diversity = Marine mass extinction Five Major Mass Extinctions Phylogenies, Ch. 25 History of descent Branching tree Speciation events are twigs History of Life
Selecting and Ordering Traits Vertebrate Cladogram Selecting and Ordering Traits Vertebrate Cladogram Selecting and Ordering Traits Vertebrate Cladogram
Selecting and Ordering Traits Vertebrate Cladogram Clarifications Convergent Evolution Marsupials – Tasmanian wolf Placentals – Grey wolf Occupy same niche, similar morphology Tasmanian wolf more closely related to all marsupials than to grey wolf Monophyly All mammals have common ancestor Two wolf species related, but not closely Uses of Phylogenies Classifications reflects evolution How often have traits evolved Success of traits Age of lineage split Evolutionary origins Biogeography, conservation, medicine Para, Poly, Mono Phyletic From 5th edition
