Forty Years Later: The Status of the “Big Five” Mass Exinctions - Marshall (2023)

Geological time intervals

Named after places where rocks came from (eg. Jurassic from Dura Mountains in Austria)

Type Section

Idea that a specific area will give you the understanding of geological time intervals

Temporal Resolution

How finely we can look at time scale and how we can refine it

Alpha diversity

How much diversity there is in a single spot (eg. pond)

Beta diversity

Amount of diversity in one spot compared to diversity in another spot (eg. Diversity in one pond vs. Diversity in another)

Comparing and contrasting

Main idea of paper

Quantified how biodiversity has changed over time due to mass extinction events, predicted a neutral process of expanding biodiversity (believed this happened in deep time), there are periods of time when we didn’t collect many rocks for geo record

Gamma diversity

Entire species count globally

Growth of biodiversity in fossil record

Expected to see constant exponential growth due to passive evolutionary processes.

Instead saw some exponential growth, then stagnancy, then decline in biodiversity

Taxonomy

science of classifying, naming, and describing organisms based on shared characteristics and evolutionary relationships

Data sources

Are incomplete and not completely reliable

Sea level affecting the # of species we interpret

Some rocks during low sea level periods are now underwater (leads to erosion), more shallow water for rocks to be deposited in and for species to live in

We can’t fully know the amount of species in that sea level time period or know the full geological record

Economy and Power in biodiversity

economic and power (colonialism) disparities have had major impacts on our ability to understand/study/conserve biodiversity (eg. Not lots of money in africa so its harder to get a comprehensive fossil record)

Mass extinction

Substantial increase in the amount of extinctions

Greater than 75% of life dying

Major decrease in overall biodiversity

Decrease amount of speciation

Entriassic extinction

First step into dinosaurs

Encritaceous

Killed off dinosaurs

Extinction today

Rate of extinction is higher now that what is in the fossil record

Our record of this extinction may be more precise - seeing extinction in a higher resolution (temporal resolution)

Most animals we know going extinct we have a good fossil record of