Geological History and the Evolution of Life

This set of vocabulary flashcards covers the geological timescale, methods of dating fossils, factors affecting the fossil record, and major evolutionary events from the Archaean Eon through the Cenozoic Era.

Geological timescale

A scale spanning many millions of years used to understand macroevolution, subdivided into eons, eras, and periods.

Stratigraphy

The study of sedimentary rock layers where older fossils appear deeper in the earth.

Relative dating

A method to determine the age of a fossil based on its relative position in stratigraphy.

Radioisotopes

Unstable isotopes that decay and transform into stable elements over time.

Half-life

The time it takes for $\frac{1}{2}$ of a radioisotope to break down.

Genesis rock

A rock from the lunar crust formed when the moon was created, retrieved during Apollo missions to help date the earth to $4.5$ billion years.

Abiogenesis hypothesis

The hypothesis that living organisms arose from non-living organic molecules.

Miller–Urey experiment

A $1953$ experiment that attempted to simulate the conditions of the early Earth to see if organic molecules could form.

Cyanobacteria

Prokaryotic organisms that arose during the Archaean Eon and provided a major evolutionary advantage through photosynthesis.

Heterotrophs

Organisms that derive their energy from the chemical bonds within the organic molecules they consume.

Autotrophs

Organisms that directly harness energy from light or inorganic molecules.

Stromatolite

Many layers of calcified cells and sediment formed over time by autotrophic cyanobacteria.

Endosymbiosis

A process where one cell lives within another; for example, mitochondria are likely derived from alphaproteobacteria and chloroplasts from cyanobacteria.

Bilateral symmetry

A body plan found in most animals that facilitates locomotion because both sides of the body can have appendages.

Phanerozoic eon

The eon that started $543$ mya and extends to the present day, characterized by the proliferation of multicellular eukaryotic life.

Cambrian explosion

A large increase in atmospheric $O_2$ followed by a huge increase in new species, particularly marine invertebrates, between $543–490$ mya.

Vascular plants

Plants with specialized tissues for conducting water and minerals, which first arose during the Silurian Period.

Tetrapods

Four-limbed vertebrates, such as amphibians, that emerged during the Devonian Period.

Amniotic egg

A critical innovation emerging in the Carboniferous Period that enabled reptiles to move away from water and reproduce on land.

Pangaea

A supercontinent formed by continental drift during the Permian Period approximately $250$ mya.

Subduction

The process occurring at plate boundaries where a thinner oceanic plate is forced underneath a thicker continental plate.

Parasol Effect

A cooling effect caused by volcanic ash and $SO_2$ in the atmosphere blocking sunlight, which can lead to mass extinctions.

Adaptive radiation

A pattern in history where survivors of a mass extinction spread, diversify, and colonize newly open habitats.

Archaeopteryx lithographica

An early birdlike animal that emerged during the Jurassic Period.

Angiosperms

The earliest flowering plants, which emerged during the Cretaceous Period.

Iridium

A rare element on Earth often found in meteorites; a thin layer of it provides evidence for the meteorite impact at the end of the Cretaceous Period.

Hominoids

A group that emerged ~$7$ mya including humans, chimpanzees, gorillas, orangutans, and gibbons.

Hominins

A group including modern humans, extinct human species, and their immediate ancestors.

Homo sapiens

Modern humans who first appeared about $200,000$ years ago and spread throughout the world.