extinction

How many species are estimated to have evolved on Earth over the last 3.5 billion years?

Approximately 4 billion species.

What percentage of species that evolved on Earth are now gone?

99%.

What defines a mass extinction event?

When Earth loses more than ¾ of its species in a geologically short interval.

How many mass extinctions have occurred in the past 540 million years?

Five mass extinctions.

What was the cause of the Ordovician mass extinction?

Onset of alternating glacial and interglacial episodes and changes in atmospheric and ocean chemistry.

What percentage of species were lost during the Devonian mass extinction?

75%.

What factors contributed to the Permian mass extinction?

Siberian volcanism, global warming, ocean acidification, and possible meteor impact.

What was a significant factor in the Triassic mass extinction?

Elevated atmospheric CO2 leading to increased temperatures and ocean acidification.

What caused rapid cooling during the Cretaceous mass extinction?

A meteor impact.

What percentage of total extinctions do mass extinctions account for?

4%.

How long does it typically take for biodiversity to recover after a mass extinction?

About 10 million years.

How many species are currently threatened with extinction according to the IUCN Red List?

27,000 animal and plant species.

What percentage of birds are threatened with extinction?

14%.

What are R-selected traits that promote survival?

Large populations, widespread distribution, high genetic variability, rapid dispersal, and human commensalism.

What are K-selected traits that increase vulnerability to extinction?

Small populations, rarity, low genetic variability, slow dispersal, and exploitation by humans.

What are characteristics of R species?

Opportunistic pioneers, rapid reproduction, unstable habitats, small body size, and high adult mortality.

What are characteristics of K species?

Specialists that favor populations near carrying capacity, large body size, slow growth, and high parental care.

What demographic factors make small isolated populations vulnerable to extinction?

Unequal sex ratio, low chance of finding a partner, and low cooperative interaction.

How does genetic diversity affect small isolated populations?

Lower genetic diversity limits their ability to respond to new conditions and increases inbreeding, leading to higher offspring mortality.

What is the extinction vortex?

A cycle where small populations become increasingly vulnerable to extinction due to demographic, genetic, and environmental factors.

What predispositions increase the likelihood of extinction?

Rarity, large size, slow growth, long lifespan, large area requirements, and specialized needs.

What is the current status of extinction as a natural process?

Extinction is a natural process, and while there have been five mass extinctions, we may be entering a sixth.