History of life on earth

ways to determine ages

• stratigraphy

• relative dating

• radiometric dating

stratigraphy

fossils in sedimentary rocks appear deeper in earth

relative dating

determine age of fossil based on position in stratigraphy

radiometric dating

age based on isotopic decay

• forms into stable elements

• half life

Abiogenesis hypothesis

living organisms arised from non living organic molecules

Archean eon

• origin of life (prokaryotes)

• anaerobic (glycolysis)

Proterozoic eon

• first colonial cyanobacteria

• first eukaryotes

  • invertebrates

  • bilateral symmetry

• aerobic respiration

phanerozoic eon

• 3 eras: Paleozoic, Mesozoic, Cenozoic

Paleozoic era - Cambrian Period

• Cambrian explosion: O2 ^ = new species (marine)

Paleozoic era - Ordovician Period

• colonization of land by plants & animals

• hard shelled marine

• large glaciers = shallow oceans → mass extinction

Paleozoic era - Silurian Period

• early vascular plants

• more colonization of land by terrestrial plants & animals

• seed plants

Paleozoic era - devonian period

• gymnosperms emerged

• insects

• tetrapods

• more extinctions of marine species

tetrapods

• amphibians

• gain of limbs

Paleozoic era - carboniferous period

• flying insects emerged

• more amphibians

• larger plants/trees

• amniotic egg

Paleozoic era - Permian period

• Continental drift: Pangaea

• more gymnosperms

• reptiles dominant

• mass extinction : 90-95% of marine/terrestrial

Mesozoic Era - Triassic Period

• first dinosaurs

• first mammals

Mesozoic era - Jurassic Period

• dinosaurs and reptiles dominant

• early birdlike animal

Mesozoic era - Cretaceous period

• angiosperms emerged

• mass extinction of dinosaurs and reptiles

Cenozoic era - tertiary period

• mammals dominant

• angiosperms dominant

• hominoids (humans, chimps)

Cenozoic era - quaternary period

• ice ages

• extinction of large mammals

• hominins diversified

• homo sapiens