History of Earth & Human Society: Biodiversity and Climate Trends

This flashcard set covers the geological history of Earth's biodiversity, major mass extinction events, the carbon cycle, and the impacts of human-induced climate change.

Ediacaran fossils

Simple-shaped Macroscopic fossils of organisms thought to be animals that first appear in rocks deposited approximately $565$ million years ago.

Cambrian Explosion

A period occurring from $541-520$ MYA characterized by the rapid diversification of aquatic life and the appearance of most modern body plans.

Biomineralization

A key innovation during the Cambrian period involving the development of hard parts such as skeletons made of silica, calcium carbonate, and calcium phosphate.

Substrate Revolution

The shift toward active burrowing by marine organisms that occurred during the Cambrian Explosion.

Tiktaalik

A transitional fossil displaying both fish and tetrapod traits, including wrist-like bones for support, gills for underwater breathing, and primitive lungs for breathing air.

Evolution of woody plants

An event between $400-350$ MYA that caused a dramatic decline in atmospheric $CO_2$ levels through biological influence on geological cycles.

The Big Five

A series of rare mass extinction events among complex, multicellular organisms that have significantly altered the course of evolution.

End-Permian Extinction

The most devastating mass extinction occurring $252$ million years ago, resulting in the loss of ~$90-96\%$ of marine species and ~$70\%$ of terrestrial species.

Cretaceous Mass Extinction

An event approximately $65$ MYA caused by a large asteroid impact ($\text{Chicxulub crater}$) and volcanic activity ($\text{Deccan Traps}$) that eliminated ~$75\%$ of species, including non-avian dinosaurs.

Mass Extinction (Definition)

A short period of time when at least $75\%$ of species are lost.

Amphibians

Often called the 'canary of the gold mine' for ecosystems because their narrow environmental tolerances and gas exchange through skin make them sensitive to disruption.

Greenhouse Gases

Atmospheric components such as $CO_2$, water vapor, and methane ($CH_4$) that absorb and trap heat; excessive levels put life at risk through increased greenhouse effect.

Sedimentary rock

The largest and typically long-term reservoir for carbon within the global carbon cycle.

Keeling Curve

A record of atmospheric $CO_2$ levels over the past $60$ years showing a seasonal pattern based on plant photosynthesis and a steady long-term increase.

The Deadly Trio

The three effects of increasing $CO_2$ on the oceans: increased temperature (warming), decreased pH (acidification), and decreased capacity to store oxygen (deoxygenation).

Positive Feedbacks

Destabilizing climate processes such as soil respiration increases or permafrost thawing that release more $CO_2$ and $CH_4$, strengthening the greenhouse effect.

CO2 Fertilization

The phenomenon where increased atmospheric $CO_2$ increases photosynthesis and plant growth, though often resulting in decreased nutrient quality for crops.