Question 1

Which of the following best describes the 'Sixth Extinction' as presented in Kolbert's book?

Accepted Answer

A mass extinction event currently underway, primarily driven by human activities such as habitat destruction, climate change, and species introductions.

Question 2

According to Kolbert, what is the primary reason amphibians are considered the most endangered class of animals today?

Accepted Answer

Their extinction rate is up to forty-five thousand times higher than the background rate, largely due to the spread of the chytrid fungus and habitat loss.

Question 3

Which of the following best explains the 'species-area relationship' ($$S = cA^z) $$and its significance in predicting extinction rates?

Accepted Answer

It predicts that as the area of a habitat decreases, the number of species it can support declines in a predictable, non-linear way, allowing scientists to estimate species loss from habitat destruction.

Question 4

Which of the following is a key difference between background extinction and mass extinction events, as defined in the book?

Accepted Answer

Background extinction is the normal, low-level process of species loss, while mass extinction is a rapid, global event that eliminates a significant proportion of the world's biota in a geologically short time.

Question 5

What evidence did Walter Alvarez and his colleagues use to support the hypothesis that an asteroid impact caused the end-Cretaceous mass extinction?

Accepted Answer

A global layer of clay rich in iridium, shocked quartz, and the discovery of the Chicxulub crater.

Question 6

Which of the following best describes the 'Anthropocene' as discussed by Kolbert?

Accepted Answer

A proposed epoch marked by significant human impact on Earth's geology and ecosystems, including climate change, species extinctions, and biogeochemical cycles.

Question 7

Why are calcifying marine organisms, such as corals and some plankton, particularly vulnerable to ocean acidification?

Accepted Answer

Because acidification reduces the concentration of carbonate ions ($$\mathrm{CO}_3$$^{2-}$$), increasing the energy required for calcification and eventually causing shells and skeletons to dissolve.

Question 8

Kolbert describes the 'New Pangaea' as a result of which human activity?

Accepted Answer

The global mixing of species through trade, travel, and deliberate introductions, effectively reuniting the world's biota into a single supercontinent.

Question 9

Which of the following is an example of a 'novel interaction' leading to extinction, as discussed in the book?

Accepted Answer

The introduction of the chytrid fungus ($$Batrachochytrium\ dendrobatidis) to $$amphibian populations that had no prior exposure, resulting in catastrophic die-offs.

Question 10

What is the 'Signor-Lipps effect' and how does it affect our interpretation of the fossil record?

Accepted Answer

It describes how sudden extinction events can appear gradual in the fossil record because rare species are less likely to be preserved, 'smearing out' the timing of their disappearance.

Question 11

Kolbert discusses the 'megafauna extinction' at the end of the Pleistocene. What is the leading hypothesis for the cause of these extinctions?

Accepted Answer

Overhunting by humans, whose arrival in new regions closely matches the timing of megafauna disappearances.

Question 12

Which of the following best illustrates the concept of 'biotic attrition' as used in the book?

Accepted Answer

The gradual loss of species from tropical regions as climate zones shift and suitable habitats disappear, with few new species evolving to replace them.

Question 13

What is the main reason that mass extinctions are considered to 'suspend the usual rules of survival'?

Accepted Answer

Because conditions change so drastically and/or suddenly that traits previously advantageous may become fatal, and evolutionary history offers little protection.

Question 14

Which of the following is a real-world example from the book of how invasive species can lead to extinction of native species?

Accepted Answer

The introduction of the brown tree snake ($$Boiga\ irregularis) to $$Guam, which led to the extinction of many native birds and mammals.

Question 15

Kolbert describes the 'leaky replacement' hypothesis regarding Neanderthals and modern humans. What does this hypothesis propose?

Accepted Answer

That before Neanderthals went extinct, they interbred with modern humans, and as a result, non-African humans today carry 1–4% Neanderthal DNA.

Question 16

Why does Kolbert argue that the current rate of environmental change is especially dangerous for many species?

Accepted Answer

Because the rate of change is much faster than in past events, giving species little time to adapt or migrate, leading to higher extinction risk.

Question 17

Which of the following best summarizes Kolbert's conclusion about humanity's role in the Sixth Extinction?

Accepted Answer

Human activities have become a geologic force, driving a mass extinction event that will shape the future of life on Earth long after our own species is gone.

The Sixth Extinction: Mass Extinction, Biodiversity, and Human Impact – Study Notes for General Biology

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