Earth History

07/10/22

Archean

* 3.8 – 2.5 BYA
* Origin of life
* First microfossils are from 3.5 BYA

Proterozoic

* 2.5 BYA – 541 MYA
* A lot more fossil evidence and what happened during this time
* There was an oxidative atmosphere
* Several glaciation periods
* Eukaryotes
* Multicellularity

Periods in Proterozoic

* Paleoproterozoic
* Mesoproterozoic
* Neoproterozoic

Paleoproterozoic

* 2.5 – 1.6 BYA


* Great oxygenation event
* Drop in greenhouse gases
* Cooling period on the planet
* Triggered Huronian glaciation
* Oxygen was hugely toxic to most organisms at the time
* Primary endosymbiosis

Great Oxygenation Event

* Huge increase in oxygen levels
* Most likely because of cyanobacteria photosynthesis

Huronian glaciation

Caused mass extinction of life

Primary Endosymbiosis

* 2 BYA
* Origin of eukaryotes
* Diversified rapidly
* Formed crown groups if eukaryote lineages

Mesoproterozoic

* 1.6 – 1 BYA
* Development of sexual reproduction
* Unicellular organisms diversified
* Secondary endosymbiosis

Secondary Endosymbiosis

First glaucophytes, red, and green algae

Neoproterozoic

* 1000 – 541 MYA
* Snowball Earth,
* Origin of multicellular life forms - fossil evidence of this


* Split of major animal lineages (800 – 600 MYA) – sponges, cnidarians, protostomes, deuterostomes
* First fungi and charophytes,


* Formation of the ozone layer

Charophytes

Sister group of plants

Ozone Layer

* Made of O3
* Blocks UV light
* Enabled colonisation of land

Snowball Earth

* Earth has been almost fully covered by ice (twice)
* Life survived in very small areas
* Rapid alternations of glacial and hot periods
* Due to volcanic activity, which generated ash and greenhouse gases

Phanerozoic

* 541 MYA - now
* Complex life forms diversified
* Several mass extinctions

Periods of Phanerozoic

1. Palaeozoic
2. Mesozoic
3. Cenozoic

Mesozoic

Age of reptiles and conifers

Cenozoic

Age of mammals

Cambrian

* 541 – 495 MYA
* All modern animal phyla and groups are represented here
* First vertebrates and cephalopods (e.g., octopus)


* Trilobites (arthropods) are abundant
* Knowledge about this period comes from Burgess Shale fossils

Ordovician

* 495 – 443 MYA
* Oceans dominated by invertebrates
* Evolution led to armoured fishes

Silurian

* 443 – 417 MYA
* Major shift – first clear fossil evidence of life on land
* Evolution of first jawed fishes, coral reefs, terrestrial plants, lycophytes, fungi and animals

Devonian

* 417 – 354 MYA
* First terrestrial vertebrates (amphibians), bony fishes, sharks, insects, stonewort, ferns and lichens

Carboniferous

* 354 – 290 MYA
* First reptiles and conifers
* Winged insects (dragon flies)
* Seed ferns abundant
* Major coal deposition
* Peak in oxygen levels

Permian

* 290 - 248 MYA
* Insects diversify (beetles first)
* Separation of reptile lineages
* Cycads and conifers

Triassic

* 249 - 205 MYA
* First dinosaurs
* First turtles
* First flies
* Cycads and conifers

Jurassic

* 204 - 142 MYA
* Dinosaurs dominant terrestrial megafauna
* First mammal, birds, crocodiles
* Gymnosperm forests

Cretaceous

* 142 - 65 MYA
* Angiosperms evolve
* First bees and ants

Cenozoic

* 65 MYA - now
* Diversification of placental mammals
* Origin of all mammalian families
* Diversification of birds
* Radiation of angiosperms (grasses)

Cenozoic Eras

* Paleogene
* Neogene
* Quaternary

Five Major Mass Extinctions

* Ordovician-Silurian
* Late Devonian
* Permian-Triassic
* Triassic-Jurassic
* Cretaceous-Paleogene

Ordovician-Silurian

* 445 - 440 MYA
* Massive ice age
* Sea level drop 70 m - 100 m
* Rapid temperature rise
* Major loss of marine life

Late Devonian

* 375 - 359 MYA
* Temperature drop
* Oxygen depletion in oceans
* Loss of armoured fish and reef ecosystems

Permian-Triassic

* 252 MYA
* Fast temperature rise
* Greenhouse gases, CO2 and methane
* 90% of species extinct
* Loss of trilobites and most reptiles

Triassic-Jurassic

* 201 MYA
* Volcanic eruptions
* Sea levels falling
* Loss of large amphibians

Cretaceous-Paleogene

* 66 MYA
* Asteroid impact
* Sea levels fall 150 m
* Temperature increases
* Loss of non-avian dinosaurs
* Pterosaurs
* Marine reptiles
* Ammnoites