The Emergence of Humankind - Vocabulary Flashcards

Phanerozoic Eon

• Fourth and current geologic eon; from 541 ext{ mya} to present

• Divided into three eras: Paleozoic, Mesozoic, Cenozoic

Paleozoic Era

• Spanned six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian

• Cambrian Period (541 ext{ to } 485 ext{ mya})

  • All life confined to oceans

  • Earliest lifeforms: worms, jawless fishes; chordates; arthropods (e.g., trilobites)

  • End of Ordovician: horseshoe crab reach shores

• Ordovician Period (485 ext{ to } 443 ext{ mya})

  • Marine life becomes diverse; early vertebrates flourish

• Silurian Period (443 ext{ to } 419 ext{ mya})

  • Many plants and animals appear, mainly along seashores

  • Notable early arthropods: sea scorpions, centipedes, arachnids

• Devonian Period

  • Fishes achieve greatest diversity; bony, jawed fishes; lobefins

  • Some bony fishes move onto land; respiration via skin noted

• Carboniferous Period (358 ext{ to } 299 ext{ mya})

  • Seashore ecosystems move inland; forests with woody stems

  • Ferns and seeded plants proliferate; lush forests

  • Oxygen levels rise; giant amphibians; earliest reptiles

• Permian Period (299 ext{ to } 252 ext{ mya})

  • Formation of Pangaea; varied, extreme climate

  • Reptiles become dominant on land; therapsids are early mammal ancestors

Mesozoic Era (Age of Reptiles)

• Triassic Period (252 ext{ to } 201 ext{ mya})

  • Reptiles fill ecological void after mass extinctions

  • Surviving amphibians present; early mammals small and nocturnal insectivores

  • Marine reptiles (ichthyosaurs, plesiosaurs) prominent

  • End of Triassic: several reptiles extinction; dinosaurs become dominant land animals

• Jurassic Period (201 ext{ to } 145 ext{ mya})

  • Dinosaurs dominate land; diversification accelerates

  • Sauropods: large, herbivorous

  • Three major groups highlighted: theropods (bipedal, carnivorous); pterosaurs (winged)

• Cretaceous Period (145 ext{ to } 66 ext{ mya})

  • Dinosaurs remain dominant; new species appear: Iguanodon, Triceratops, Tyrannosaurus rex

  • Birds become more diverse; angiosperms (flowering plants) diversify

  • End-Cretaceous mass extinction: asteroid impact theory; dinosaurs wiped out; survivors include early mammals, birds, small reptiles

Cenozoic Era (Age of Mammals)

• Paleogene Period (66 ext{ to } 23 ext{ mya})

  • Mammals begin to evolve; birds and small reptiles survive; early whales appear

• Neogene Period (23 ext{ to } 2.5 ext{ mya})

  • Mammals widespread; primates and hominids appear

• Quaternary Period (2.5 ext{ mya to present})

  • Age of Humans; multiple ice ages across the globe

Common themes and notes

• Major continents shift during Mesozoic into Laurasia and Gondwanaland; Pangaea forms and then breaks apart

• End of each era often marks major transitions in dominant life forms (marine to terrestrial, reptiles to mammals, etc.)