EARTH HISTORY

MAJOR EVENTS IN EARTH HISTORY

  • Timeline Overview:

    • Formation of Earth

    • Origin of life

    • Great oxygenation event

    • Eukaryotes

    • Multicellular life forms

    • Prokaryotes

    • Main animal lineages

    • Modern animal phyla

    • Terrestrial plants and animals

    • Major glaciation events

    • Reptiles, conifers

    • Mammals and birds

    • Angiosperms

    • Red and green algae

GEOLOGICAL EPOCHS AND BIOLOGICAL EVENTS

ARCHEAN EON (4.0 - 2.5 billion years ago)

  • Time Frame: 4.0 to 2.5 billion years ago (BYA)

  • Key Event: Origin of life

  • First Microfossils: 3.5 billion years ago, consisting of microstromatolites which are indicative of photosynthetic bacteria.

PROTEROZOIC EON (2.5 BYA – 539 million years ago)

  • Time Frame: 2.5 billion years ago to 539 million years ago (MYA)

  • Atmospheric Changes: Development of an oxidative atmosphere

  • Climate Events: Several glaciation periods occurred.

  • Biological Developments:

    • Eukaryotes emerged

    • Multicellularity evolved

PALAEO-PROTEROZOIC (2.5 - 1.6 BYA)

  • Key Events:

    • Great Oxygenation Event: Significant increase in oxygen levels (~105-fold), mostly caused by cyanobacteria through photosynthesis.

    • Oxygen Sink Effects: Iron and other compounds acted as sinks that prevented oxygen accumulation prior to the Palaeo-Proterozoic.

    • Huronian Glaciation Triggered: Resulted in a mass extinction event.

    • Primary Endosymbiosis: Occurred around 2 billion years ago leading to the origin of eukaryotic cells and the emergence of crown groups of eukaryotes.

MESO-PROTEROZOIC (1.6 - 1 BYA)

  • Key Developments:

    • Sexual Reproduction: First instances of sexual reproduction witnessed.

    • Diversification: Unicellular organisms diversified, particularly through a secondary endosymbiotic process.

    • Emergence of New Taxa: Formation of first glaucophytes, red and green algae; potential origin of eukaryotic multicellularity observed through few fossil records.

NEO-PROTEROZOIC (1,000 - 539 MYA)

  • Key Events:

    • Major Glaciation: Significant event referred to as Snowball Earth around 720 MYA.

    • Fossils of Multicellular Life: Clear evidence of multicellular organisms in the Ediacaran period at around 635 MYA.

    • Animal Lineages Divergence: Initial split in major animal lineages occurred between 800 and 600 MYA, leading to sponges, cnidarians, protostomes, and deuterostomes.

    • First Fungi and Charophytes: Early adaptations to land occur alongside the formation of an ozone layer that blocks ultraviolet radiation.

SNOWBALL EARTH

  • Description: Periods where Earth was likely nearly entirely covered by ice.

  • Survival of Life Forms: Some life forms managed to survive in localized areas, possibly experiencing rapid climate alternations between glacial phases and warm periods.

PHANEROZOIC EON (539 MYA - Present)

  • Time Frame: 539 million years ago to present.

  • Period Division:

    • Palaeozoic Era

    • Mesozoic Era: Known as the Age of reptiles and conifers

    • Cenozoic Era: Recognized as the Age of mammals

  • Key Characteristics: Evolution and diversification of complex life forms alongside several documented mass extinction events.

CAMBRIAN PERIOD (539 - 487 MYA)

  • Key Developments:

    • Animal Body Plans: All modern animal phyla represented.

    • Emergence: First vertebrates and cephalopods, with trilobites being abundant.

BURGESS SHALE FOSSILS

  • Importance: Provide significant insights into Cambrian life forms, showcasing that all major animal groups were already present during this period.

ORDOVICIAN PERIOD (487 - 443 MYA)

  • Key Flora and Fauna: Predominance of various invertebrates including armored fishes.

SILURIAN PERIOD (443 - 419 MYA)

  • Key Developments:

    • Jawed Fishes (Gnathostomes): First appearance of jawed fishes.

    • Coral Reefs: Development of the first coral reefs seen.

    • Terrestrial Evidence: The clear emergence of terrestrial plants such as lycophytes, alongside fungi and animals (with examples being arthropods such as arachnids and myriapods).

DEVONIAN PERIOD (419 - 359 MYA)

  • Key Developments:

    • First terrestrial vertebrates (amphibians) emerged.

    • Introduction of first bony fishes (teleosts), first sharks, first varieties of insects, first stoneworts, ferns, and lichens.

CARBONIFEROUS PERIOD (359 - 299 MYA)

  • Key Flora and Fauna:

    • Appearance of first reptiles (known as amniotes with cleidoic eggs).

    • Emergence of winged insects, specifically dragonflies.

    • Development of first conifers and abundant seed ferns.

    • Major coal deposits formed during this period, alongside reaching peak oxygen levels.

PERMIAN PERIOD (299 - 252 MYA)

  • Key Events:

    • Insects diversified, seeing the first beetles.

    • Notable separation of reptile lineages observed.

    • Cycads and conifers present.

TRIASSIC PERIOD (252 - 201 MYA)

  • Key Developments:

    • First dinosaurs and turtles emerge.

    • First flies recorded

    • Cycads and conifers remain prominent.

JURASSIC PERIOD (201 - 143 MYA)

  • Key Characteristics:

    • Dinosaurs became the dominant terrestrial megafauna.

    • Development of first mammals and birds, along with crocodiles.

    • Establishment of gymnosperm forests.

CRETACEOUS PERIOD (143 - 66 MYA)

  • Key Developments:

    • Evolution of angiosperms observed.

    • First appearance of bees and ants recorded.

CENOZOIC ERA (66 MYA - Present)

  • Time Frame: 66 million years ago to current.

  • Eras: Divided into Palaeogene, Neogene, and Quaternary.

  • Key Characteristics:

    • Diversification of placental mammals, marking the origin of all mammalian families.

    • Expansion of bird diversity.

    • Noteworthy radiation of angiosperms, particularly grasses.

FLUCTUATIONS IN EARTH CLIMATE

  • Significance: Notable dramatic changes in Earth climate have had major impacts on various life forms, highlighted by five significant mass extinctions observable in the fossil record.

FIVE MAJOR MASS EXTINCTIONS

  1. Ordovician-Silurian (445-440 MYA): Massive ice age leading to a sea level drop of 70-100 m, rapid subsequent temperature rise, resulting in a significant loss of marine life.

  2. Late Devonian (375-359 MYA): Notable temperature drop leading to oxygen depletion in oceans which was caused by nutrient inflow from land; consequent loss of armored fish and reef ecosystems.

  3. Permian-Triassic (252 MYA): Rapid temperature increase attributed to greenhouse gases (CO2 and methane) leading to the extinction of over 90% of species, including trilobites and most reptiles.

  4. Triassic-Jurassic (201 MYA): Volcanic eruptions and falling sea levels contributing to the loss of large amphibians and most mammal-like reptiles.

  5. Cretaceous–Palaeogene (66 MYA): Asteroid impact combined with falling sea levels (150 m) and temperature spikes led to the extinction of non-avian dinosaurs, pterosaurs, marine reptiles, and ammonites.

  • Consequences: Major biodiversity loss followed by the enablement of new organism groups’ evolution; these events are interlinked with global climate changes attributed to volcanic activities and plate tectonics.

REMINDER: CONTINENTAL DRIFT

  • Illustrations: Series of maps showing the positioning of continental plates over 225 MYA, 135 MYA, and 65 MYA.

  • Key Plates: Pacific Plate, Laurasia, Gondwana, and American, African, and Antarctic plates.

MAN-MADE 6TH MASS EXTINCTION?

  • Concerns: Anthropogenic climate change is predicted to drive global temperatures back to levels not seen for 35 million years, leading to the following potential outcomes:

    • Loss of ice caps.

    • Significant sea level rise.

    • Substantial biodiversity loss driven by habitat destruction, exploitation, and climatic changes.

KEY REFERENCES

  • Studies: Westerhold et al. (2020).

  • Data Sources: Observable statistics from Our World in Data on the global living planet index.

SUMMARY: EARTH HISTORY IN 24 HOURS

  • Timeline of transformative events relating to the biological and geological evolution of life on Earth, including key milestones such as:

    • First modern human (59:59.9)

    • Ice Ages (59:59.2)

    • First human ancestor (59:58.8)

    • Various mass extinction events and the emergence of key life forms throughout the Cenozoic, Mesozoic, and Paleozoic eras.

  • Notable timestamps given for significant evolutionary milestones:

    • First fish (53:25),

    • First amphibians (55:22),

    • First insects (54:59),

    • First multicelled organisms, seaweed and algae (41:45),

    • First cells with a nucleus (40:26).