Macroevolution: The Long Run

These flashcards cover essential topics related to macroevolution, adaptive radiation, extinction rates, and the impact of human activities on biodiversity.

What is macroevolution?

Evolution on a larger scale, above the species level, involving origination, diversification, and extinction of species over long periods of time.

What does the origination rate (α) refer to?

The rate at which new species or larger clades appear.

What is the extinction rate (Ω)?

The rate at which existing species or clades disappear.

What is standing diversity?

The number of species present at a given time.

What is the formula for turnover in macroevolution?

Turnover = originations (α) + extinctions (Ω).

What does a high turnover rate indicate?

High rates of new species formation compared to extinctions.

What are the three observations about fossil distribution?

Standing diversity, origination rate (α), and extinction rate (Ω).

What is adaptive radiation?

The rapid production of many descendant species from a single lineage with more originations than extinctions.

What are the three hallmarks of an adaptive radiation?

Monophyletic group, rapid speciation, and ecological diversification into many niches.

What triggers adaptive radiations?

Empty niches and key innovations.

What caused the Cambrian radiation of animals?

Environmental change and key innovations like genetic toolkit and skeletal structures.

What innovation was crucial for the Cretaceous radiation of angiosperms?

The development of flowers, which initiated mutualistic coevolution with insects.

What does mass extinction describe?

A statistically significant departure from background extinction rates causing substantial taxonomic diversity loss.

How many mass extinctions has Earth experienced?

Five mass extinctions over the past 500 million years.

What event was the greatest mass extinction?

The end-Permian extinction, which claimed 96% of all species.

What is background extinction?

The normal rate of extinction for species or clades.

What happened to trilobites at the end of the Ordovician period?

Trilobites dramatically declined and eventually went extinct at the end of the Permian period.

What is the relationship between species origination rate and extinction rate?

A clade will endure only if its origination rate (α) is greater than its extinction rate (Ω).

What triggers mass extinctions involving Large Igneous Provinces?

Massive volcanic activity that can last for thousands or millions of years.

Which human actions are contributing to the current sixth mass extinction?

Habitat loss, over-harvesting, and invasive species.

What is the current average extinction rate of vertebrates compared to the background rate?

Up to 114 times higher than the background extinction rate.

What role do climate change and habitat modification play in extinction?

They exacerbate extinction risks by altering environments and reducing available habitats.

What impact does human population density have on species extinction?

Higher human population density often correlates with increased extinction rates due to habitat destruction.

What is the significance of the Hawaiian silversword radiation?

It represents diversification into many species with divergent traits after colonization of the Hawaiian archipelago.

How does pollinator specificity affect plant evolution?

It drives coevolution, leading to innovations such as nectar spurs in flowers for attracting specific pollinators.

How many species of tigers are estimated to survive today in their original habitat?

Only about 3800 tigers remain in approximately 7% of their original habitat.

What are the consequences of increased carbon dioxide levels due to human activity?

Altering atmosphere, contributing to climate change, and impacting extinction rates.