The History of Life on Earth Flashcards

Vocabulary flashcards covering the history of life on Earth, geological dating methods, physical environmental changes, and major biological events across different eras.

Sedimentary rocks

Rocks formed by the accumulation of sediments often on the bottom of a body of water.

Strata

The layers of rock where the oldest lie at the bottom and successively higher layers are progressively younger.

Stratigraphy

The study of geological strata which combines observations of fossils with the understanding of strata.

Radiometric dating

A method of determining the age of objects such as fossils and rocks based on the decay rates of radioactive isotopes.

Half-life

The time required for half of a sample to decay to its stable, nonradioactive form.

Continental drift

The gradual movements of the world’s continents that have occurred over billions of years.

Plate tectonics

The geophysics of the movement of major land masses, explaining that Earth's outermost layer is broken into major and minor plates that move from $2$ - $15\,cm$ per year.

Climate

Long-term average expectations over the various seasons, typically changing very slowly over $5,000$ - $10,000$ years.

Weather

Daily events at a given location that often change rapidly.

Mass extinctions

Events in which large portions of the species living at the time disappeared.

Quaternary period

The current and most recent period in geologic time, marked by glacial advances and warmer interglacial intervals.

Asteroids

Large rocky bodies orbiting around the sun.

Meteorite

An asteroid that has collided with Earth.

Banded iron formations

Alternating layers of red and dark rock formed by the precipitation of iron oxide when oxygen reacted with dissolved iron.

Cyanobacteria

$O_2$-generating bacteria that formed rocklike structures called stromatolites.

Stromatolites

Rocklike structures formed by oxygen-generating bacteria that are abundantly preserved in the fossil record.

Biota

All the organisms—animals, plants, fungi, and microorganisms—found in a given area at a certain time.

Flora

All the plants in a particular place and time.

Fauna

All the animals in a particular place and time.

Precambrian Era

An informal unit of geologic time subdivided into the Hadean, Archean, and Proterozoic eons, where life was largely microscopic prokaryotes.

Cambrian explosion

A rapid diversification of multicellular life that took place during the Cambrian period where many major animal groups first appeared.

Ordovician Period

A period marked by a radiation of marine organisms like filter-feeders and the first vertebrates (fish), ending with a mass extinction of $75\%$ of animal species.

Silurian Period

A period where marine life rebounded, fishes developed moveable jaws, and the first vascular plants and terrestrial animals (arthropods) appeared.

Devonian Period

Known as the Age of Fishes; it saw the emergence of the first tetrapods, the first forests, and ended with a mass extinction of about $75\%$ of marine species.

Tetrapods

Four-limbed vertebrates that first appeared during the Devonian period.

Carboniferous Period

A period characterized by swamp forests that formed coal, the evolution of wings in insects, and the dominance of amphibians.

Amniotes

Vertebrates with well-protected eggs that can be laid in dry environments.

Pangaea

A single supercontinent formed when the continents merged during the Permian period.

Permian-Triassic extinction event

Known as the “Great Dying,” it was Earth’s most severe extinction event where about $96\%$ of all multicellular species became extinct.

Laurasia

The northern large continent formed when Pangaea divided during the Jurassic period.

Gondwana

The southern large continent formed when Pangaea divided during the Jurassic period.

Angiosperms

Flowering plants that first appeared late in the Jurassic period.

Cretaceous Period

A period where modern-day southern continents rifted from Africa, dinosaurs diversified further, and snakes appeared, ending with a meteorite-caused mass extinction.

Greenhouse effect

The trapping of the sun’s warmth, which occurred during the early Paleogene due to high levels of atmospheric $CO_2$.

Holocene

The current epoch within the Quaternary period.