Which of the following statements concerning past or present mass extinctions is TRUE?

Question

BlackTom AI · Accepted Answer

The modern (Holocene/Anthropocene) extinction is characterized by losses across body sizes and ecosystems: humans drove the late Quaternary extinctions of many large megafauna (e.g., woolly mammoths, giant ground sloths, the passenger pigeon) but also caused declines and extinctions among small animals and reef organisms through habitat loss, overexploitation, introduced species, disease, and climate-driven ocean changes.

Relevant knowledge points and concepts
- Late Quaternary and ongoing (Holocene/Anthropocene) extinction: a human-accelerated event affecting many taxa.
- Megafaunal extinctions were highly visible, but extinction risk and observed losses also affect small vertebrates, invertebrates, amphibians, and reef-building corals.
- Drivers include habitat destruction, overhunting, invasive species, pathogens (e.g., chytrid fungus in amphibians), ocean warming/acidification, and coral bleaching.

Step-by-step reasoning
1. Historical record: many large mammals and birds disappeared in the last tens of thousands of years (megafauna). Those are prominent victims, which is true.
2. Contemporary biodiversity data show numerous small species are threatened or already extinct: amphibians have experienced severe declines (a large fraction are threatened or declining globally), many freshwater fishes and invertebrates have been lost, and insect biomass declines have been documented.
3. Coral reefs have suffered widespread bleaching and population loss from warming, acidification, pollution, and overfishing; reef-building corals and associated organisms have experienced local and regional extinctions.
4. Because these documented declines span both large megafauna and many small/reef species, the statement that the most recent mass extinction also claimed many small animals and reef organisms is correct.

Calculations
- No numerical calculation needed; reasoning is based on documented extinction and threat patterns (IUCN assessments, scientific literature).

Why the correct answer is correct
- Empirical evidence shows both megafaunal losses and extensive declines/extinctions among small animals (e.g., amphibians, invertebrates) and reef organisms. Thus the chosen statement accurately summarizes the pattern of the recent extinction.

Why the other options are incorrect or misleading
- Permian extinction: primarily linked to Siberian Traps volcanism and consequential environmental changes; suggestions about coal burning/thermogenic gases exist but are part of volcanic-driven mechanisms and the option overstates certainty.
- K–Pg claim: non-avian dinosaurs died, and mammals later diversified, but other groups (birds, crocodilians) survived; mammals were not necessarily the immediate first dominants across all ecosystems.
- Continental breakup: plate tectonics and continental separation alter environments over long timescales but are not typically framed as direct causes of the major abrupt mass extinctions.
- “All” mass extinctions due only to volcanism, impacts, or abrupt climate change is too exclusive; multiple interacting causes (sea-level change, ocean anoxia, biotic factors) often contributed.

Conclusion
The true statement is: "Although big megafaunas were its most prominent victims, the most recent mass extinction also claimed many small animals and reef organisms." This matches the provided correct answer.

Which of the following statements concerning past or present mass extinctions is TRUE?单项选择题

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