History of Life and Extinctions

These flashcards cover key concepts, events, and terminology relating to the history of life on Earth and the extinctions that have shaped our planet.

Archean Eon

The oldest eon in Earth's history, characterized by the formation of the Earth's crust and earliest signs of life.

Proterozoic Eon

Eon from 2.5 billion years ago to about 540 million years ago, during which the first multicellular life forms evolved.

Phanerozoic Eon

The current geological eon, spanning from 541 million years ago to the present, characterized by abundant animal and plant life.

Paleozoic Era

An era from 541 to 252 million years ago, featuring the diversification of marine life and the first plants and animals on land.

Mesozoic Era

Known as the age of reptiles, including the Triassic, Jurassic, and Cretaceous periods, spanning from 252 to 66 million years ago.

Cenozoic Era

The current geological era, known as the age of mammals, beginning 66 million years ago.

Carboniferous period

A period within the Paleozoic Era where vast swampy forests thrived, leading to massive coal deposits.

Quaternary Period

The most recent period of the Cenozoic Era, characterized by repeated glaciations and the evolution of humans.

Ordovician-Silurian extinction

The first of the 'Big Five' extinctions, occurring about 444 million years ago, likely caused by global cooling and sea level changes.

Late Devonian extinction

The second 'Big Five' extinction (375-360 million years ago), which primarily affected marine life, especially reef-building organisms.

End-Permian extinction

The third and largest 'Big Five' extinction, killing about 96% of marine species; often called 'The Great Dying.'

Triassic-Jurassic extinction

The fourth 'Big Five' extinction, occurring 201 million years ago, which allowed dinosaurs to dominate the Mesozoic.

Cretaceous-Paleogene (K-Pg) extinction

The fifth 'Big Five' extinction, 66 million years ago, famous for the extinction of non-avian dinosaurs due to an asteroid impact.

Stromatolites

Layered sedimentary formations produced by the activity of cyanobacteria, indicating early life on Earth.

Mass extinction

A significant and rapid decrease in the number of species on Earth, often caused by catastrophic events.

Cyanobacteria

Photosynthetic bacteria that played a key role in oxygenating the Earth's atmosphere.

Cambrian explosion

A rapid diversification of life forms occurring approximately 541 million years ago, during which most major animal phyla appeared.

Great Oxidation Event

The gradual increase of molecular oxygen in Earth's atmosphere due to photosynthetic cyanobacteria.

Banded iron formations (BIFs)

Sedimentary rocks that indicate the presence of oxygen in ancient oceans, formed from iron reacting with oxygen.

Anaerobic life

Life forms that do not require oxygen for metabolism and may be harmed by it.

Eukaryotic life

Complex life forms with cells that contain a nucleus, emerging after prokaryotic organisms in Earth's history.

Mass volcanic eruptions

Significant volcanic activity that can lead to mass extinctions by altering climate and blocking sunlight.

Impact events

Collisions with celestial bodies (like asteroids) that can cause mass extinctions due to climatic and physical effects.

Climate change

Long-term alteration in temperature and typical weather patterns in a place, contributing to extinction events.

Fossil evidence

Physical evidence of past life forms preserved in geological formations, crucial for understanding Earth's biological history.