Mammalian diversity dropped at the K-Pg boundary but then rapidly increased afterward. Which best explains this rebound?

Answer: Adaptive radiation into niches vacated by non-avian dinosaurs The K-Pg extinction eliminated non-avian dinosaurs and freed many ecological niches. Mammals diversified rapidly to occupy them, an example of post-extinction adaptive radiation.

Current extinction rates are estimated at

Answer: 100-1,000× the background rate, often called the 'sixth mass extinction' Habitat loss, climate change, invasive species, and overharvesting have driven extinction rates to mass-extinction levels.

Answer: Open ecological niches that surviving lineages can radiate into (e.g., mammals after the K-Pg extinction) Mass extinctions reset evolutionary trajectories — surviving lineages diversify into vacated niches, often producing new dominant groups.

AP Biology · Topic 7.11

Extinction Practice

Part of Natural Selection.(EVO-1.K)

Practice questions

Want a predicted score for the whole AP BIO exam? Take the 20-question diagnostic and Lumi will plan the rest.

Take diagnosticarrow_forward Practice all 7.11

Sample questions

4 of 4 — sign in to practice the rest with adaptive difficulty and mastery tracking.

Sample 1difficulty 1/5
$Mammalian diversity dropped at the K-Pg boundary but then rapidly increased afterward. Which best explains this rebound?$
- A
  $Sympatric speciation alone created the increase$
- B
  $Adaptive radiation into niches vacated by non-avian dinosaurs$
  check_circle
- C
  $All extant mammals derived from a single founder$
- D
  $Hardy-Weinberg equilibrium maintained mammal diversity$
Why
$The K-Pg extinction eliminated non-avian dinosaurs and freed many ecological niches. Mammals diversified rapidly to occupy them, an example of post-extinction adaptive radiation.$
View full solution & statsarrow_forward
Sample 2difficulty 2/5
$Current extinction rates are estimated at$
- A
  $100-1,000\times the background rate, often called the 'sixth mass extinction'$
  check_circle
- B
  $Below the background rate, indicating an unusually stable evolutionary period$
- C
  $Approximately equal to the background rate, with no detectable acceleration$
- D
  $Decreasing steadily as conservation efforts offset historical biodiversity losses$
Why
$Habitat loss, climate change, invasive species, and overharvesting have driven extinction rates to mass-extinction levels.$
View full solution & statsarrow_forward
Sample 3difficulty 2/5
$Mass extinctions$
- A
  $Halt natural selection on surviving lineages until pre-extinction community structures are fully restored$
- B
  $Reset biodiversity to a uniform low level by removing the same fraction of every taxonomic group equally$
- C
  $Eliminate all evolutionary novelty because the surviving lineages cannot diversify into the vacated habitats$
- D
  $Open ecological niches that surviving lineages can radiate into (e.g., mammals after the K-Pg extinction)$
  check_circle
Why
$Mass extinctions reset evolutionary trajectories — surviving lineages diversify into vacated niches, often producing new dominant groups.$
View full solution & statsarrow_forward
Sample 4difficulty 2/5
$The bar chart shows the magnitude of the "Big Five" mass extinctions.$
$Which event, indicated by the tallest (filled) bar, was the most severe?$
- A
  $Devonian$
- B
  $Permian-Triassic (P-T)$
  check_circle
- C
  $Cretaceous-Paleogene (K-Pg)$
- D
  $Ordovician-Silurian$
Why
$The end-Permian extinction (~252 Ma) is the most severe mass extinction in Earth's history, eliminating roughly 95% of marine species and ~70% of terrestrial vertebrate species.$
View full solution & statsarrow_forward

Predict my AP scorearrow_forward