Extinction

What is extirpation?

The disappearance of a species from a given region; also known as local extinction.

What is true extinction?

The disappearance of a species across the globe without any descendant species.

What is a mass extinction?

Temporally discrete episodes with a high rate of species loss, typically associated with abrupt and catastrophic environmental change.

What is an example of extirpation?

The gray wolf was extirpated from Yellowstone National Park by 1926.

How many mass extinction events have occurred over the last 550 million years?

Five mass extinction events.

What typically causes mass extinction events?

Abrupt climate changes resulting from natural processes.

How long does biodiversity recovery take after a mass extinction?

Tens of millions of years.

What caused the extinction of non-avian dinosaurs?

The Chicxulub asteroid or comet impact approximately 65 million years ago.

Where is the Chicxulub Crater located?

The Yucatán Peninsula in Mexico.

What is the approximate diameter of the Chicxulub Crater?

300 km.

How large was the impactor that created the Chicxulub Crater?

More than 10 km in diameter.

What environmental effects resulted from the Chicxulub impact?

Heat and shock, massive regional disturbance, huge tsunami waves, atmospheric dust causing global dimming and cooling, and acid rain.

What happened to the atmosphere following the Chicxulub impact?

Atmospheric dust caused global dimming and cooling.

What were the Deccan Traps?

A major volcanic region in India discussed as another possible contributor to dinosaur extinction.

Is extinction a random process?

No. Some types of organisms are more vulnerable to extinction than others.

What body-size traits increase extinction risk?

Larger body size and greater longevity.

What other traits increase extinction risk?

Larger home range area and vulnerability to habitat fragmentation.

What traits decrease down the food web?

Vulnerability to stress decreases, while the ability to adapt or evolve and species richness increase.

What is the relationship between species richness and extinction risk?

Higher species richness provides insurance against extinction.

What were moa?

Nine species of flightless birds in six genera that were endemic to New Zealand.

How large could the largest moa become?

About 3.6 meters tall with their necks outstretched and approximately 230 kg in weight.

What was the estimated moa population when Polynesians settled New Zealand?

Approximately 58,000 around CE 1280.

When did moa become extinct?

Approximately CE 1300–1450.

What was the primary cause of moa extinction?

Overhunting.

What was Jefferson's ground sloth (Megalonyx jeffersonii)?

The youngest and largest known species of ground sloth in North America.

When did Jefferson's ground sloth evolve?

During the Pliocene, approximately 5 million years ago.

When did Jefferson's ground sloth become extinct?

During the Quaternary extinction event, approximately 13,000 years ago.

How large was Jefferson's ground sloth?

Approximately 3 meters long and up to 1,000 kg.

What was the Kentucky coffee tree (Gymnocladus dioicus) historically associated with?

It is believed to have been an important food source for giant ground sloths.

Why are Kentucky coffee tree seed pods difficult for many modern animals to consume?

They have thick walls and contain poisonous, gooey pulp.

What is unusual about Kentucky coffee tree seed germination?

The seeds only germinate after being washed in an acid bath.

What is an evolutionary anachronism?

A species or trait that was favorably selected in the past because of coevolution with megafauna that are now extinct, resulting in reduced effectiveness or maladaptation in modern ecosystems.

Why is the Kentucky coffee tree considered an evolutionary anachronism?

It evolved characteristics suited to interactions with large animals, such as giant ground sloths, that are now extinct.

What was the cave bear (Ursus spelaeus) named after?

It was named because most of its fossils have been found in caves.

When did cave bears become extinct?

By the Last Glacial Maximum.

How much did cave bears weigh?

Approximately 350–1,000 kg.

What are examples of extinct Pleistocene megafauna?

Woolly mammoths and saber-toothed cats.

What are the four major theories explaining Pleistocene megafauna extinctions?

1. Climatic change; 2. Spreading disease; 3. Asteroid or comet impact; 4. Hunting by spreading human populations.

Were the proposed causes of Pleistocene megafauna extinction mutually exclusive?

No. Two or more factors may have combined to cause the extinctions.

What does most evidence suggest about the cause of Pleistocene megafauna extinctions?

Humans were a major contributing factor.

What is the Southern Dispersal paradigm?

A model describing the movement and dispersal of early humans across the world during the Upper Paleolithic.

When did newer evidence suggest the initial dispersal of humans into North America occurred?

Approximately 25,000–13,000 years ago.

What is Homo sapiens?

The scientific name for modern humans.

What are Clovis points?

Characteristically fluted projectile points associated with the North American Clovis culture.

When do Clovis points date to?

The Paleoindian period, approximately 13,500 years ago.

Where did Clovis points get their name?

The city of Clovis, New Mexico, where examples were first discovered in 1929.

What is the Pleistocene Overkill Hypothesis?

The hypothesis that human hunters armed with Clovis spear points overhunted naive American megafauna.

What other factors may have contributed to Pleistocene megafauna extinction besides overhunting?

Abrupt climate shifts and coupled ecological changes.

What does the extinction-rate comparison across continents show?

Extinction rates among large mammalian herbivores were much higher in North America and South America than in Africa.

Why were African species potentially better adapted to human predation and competition?

They coevolved with humans over a longer period.

Why were megafauna in the Americas more vulnerable to human hunting?

They did not coevolve with humans and were therefore naive to intense predation and competition.

Why were European and Australian megafauna also vulnerable to human hunting?

Humans arrived much later, so these species had less evolutionary experience with human predation.

What is the Sixth Mass Extinction?

The proposed current mass extinction event associated with human activities.

Which species is associated with the Sixth Mass Extinction in the lecture?

Homo sapiens.

What is the Linnaean Shortfall?

The lack of knowledge about Earth's biodiversity, including what species exist and why they are threatened or disappearing.

What are Centinelan extinctions?

Extinctions that occur without scientists ever discovering or documenting the species' existence, sometimes described as extinction without bodies.

How many non-bacterial species are estimated to exist on Earth?

Approximately 8.7 million species, according to Mora et al. (2011).

How many species have been formally named or described?

Approximately 1.7 million species, according to Mora et al. (2011).

How many species may be disappearing each year?

Estimates range from 500 to 36,000 species annually.

Which groups have the best data on extinction threats?

Mammals, birds, and amphibians.

Which groups have less information available about extinction threats?

Groups such as insects and fish.

What percentage of terrestrial species remain undiscovered?

Approximately 86%.

What percentage of oceanic species remain undiscovered?

Approximately 91%.

Have more species become extinct throughout Earth's history than are alive today?

Yes. Many more species have become extinct than are currently alive on Earth.

Is extinction a natural process?

Yes, extinction is a natural evolutionary and ecological process.

What does CHIPPO represent?

The six primary threats to biodiversity: Climate change, Habitat loss, Introduced species, Pollution, Population growth, and Overconsumption.

What does C represent in CHIPPO?

Climate change.

What does H represent in CHIPPO?

Habitat loss.

What does the first I represent in CHIPPO?

Introduced species.

What does P represent in CHIPPO?

Pollution.

What does the second P represent in CHIPPO?

Population growth or overpopulation.

What does O represent in CHIPPO?

Overconsumption.

What are the primary threats to biodiversity identified in the lecture?

Exploitation, habitat degradation and change, habitat loss, climate change, invasive species, pollution, and disease.

What percentage of biodiversity threats are attributed to exploitation in the lecture's chart?

37%.

What percentage of biodiversity threats are attributed to habitat degradation and change?

31%.

What percentage of biodiversity threats are attributed to habitat loss?

13%.

What percentage of biodiversity threats are attributed to climate change?

7%.

What percentage of biodiversity threats are attributed to invasive species?

5%.

What percentage of biodiversity threats are attributed to pollution?

4%.

What percentage of biodiversity threats are attributed to disease?

2%.

How does exploitation threaten biodiversity?

Hunting, fishing, and other forms of exploitation cause declines in animal populations.

How does habitat degradation and loss threaten biodiversity?

They destroy or reduce the quality and availability of habitats needed for species survival.

How is climate change expected to affect biodiversity threats?

It is expected to become a bigger factor over time.

How do invasive species threaten native biodiversity?

They increase competition and reduce native species biodiversity