Question

many scientists agree that most dinosaurs went extinct when an asteroid struck earth about 66 million years ago. ancestors of modern birds survived the asteroid impact, then rapidly diversified as they filled new niches and the niches left by dinosaurs. most modern groups of birds had evolved by 35 million years ago.
since this time, the rate at which birds have diversified into new species has increased. scientists have found that particularly high rates of speciation occurred in regions where mountains have recently formed. new species evolved as birds already present on these mountains became specialized to habitats that developed as mountains grew.
which statement does this information best demonstrate?
a. the formation of new niches can cause sudden or gradual geological disturbances that influence the evolution of life on earth.
b. both gradual and sudden geologic disturbances contribute to the diversity of life on earth by allowing new niches to form.
c. catastrophic events, like asteroid impacts, are mainly responsible for the evolution of life on earth.
d. gradual geological events, like mountain formation, decrease the diversity of life on earth.

Explanation:

• Analyze Option A: The passage shows new niches (from asteroid impact, a sudden event, and mountain formation, a gradual event) led to bird evolution, not that niches cause geological disturbances. So A is incorrect.
• Analyze Option B: The asteroid impact (sudden geologic disturbance) created new niches for bird ancestors to diversify. Mountain formation (gradual geologic disturbance) also created new habitats/niches, leading to bird speciation. This matches the idea that both types of disturbances contribute to life diversity via new niches.
• Analyze Option C: The passage also highlights mountain formation (gradual) as a factor in speciation, not just catastrophic events. So C is incorrect as it overemphasizes catastrophic events.
• Analyze Option D: The passage states mountain formation (gradual) increased bird speciation (diversity), so D's claim that it decreases diversity is wrong.

Answer:

B. Both gradual and sudden geologic disturbances contribute to the diversity of life on Earth by allowing new niches to form.