Macroevolution, Adaptive Radiation, and Extinction
Evolution at Large Scales
Macroevolutionary patterns
Macroevolution examines broad patterns such as diversification, extinction, major morphological innovation, and long-term trends. These outcomes arise from microevolutionary processes operating across many lineages and long timescales.
Adaptive radiation
Adaptive radiation occurs when a lineage rapidly diversifies into many forms adapted to different niches. It often follows ecological opportunity, such as colonization of new habitats or the removal of competitors.
Extinction matters
The history of life is shaped not only by origin and diversification but also by extinction, which prunes lineages and changes future evolutionary possibilities.
Drivers of large-scale diversification
Ecological opportunity
- More available niches
- Can promote rapid diversification
Mass extinction
- Removes many lineages
- Can open new ecological space
What is the best definition of adaptive radiation?
Adaptive radiation is diversification into a range of ecological roles, often relatively quickly.
Correct answer: Rapid diversification into multiple niches
How can a mass extinction influence later evolution?
Extinction reshapes the selective and ecological landscape.
Correct answer: It can eliminate dominant groups, open ecological niches, and redirect diversification in surviving lineages.
Tempo and mode
Evolutionary change can be gradual, punctuated, or variable across lineages. Debates about tempo and mode ask whether change is steady through time or concentrated in bursts linked to speciation and environmental shifts.
A trait that allows exploitation of a new niche and may increase diversification is often called a
A key innovation is a trait associated with access to new adaptive zones.
Correct answer: key innovation
Macroevolution reasoning
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1
Separate patterns from processes: ask what the long-term pattern is.
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2
Identify whether diversification, extinction, or both are involved.
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3
Look for ecological opportunity or major environmental change.
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4
Connect large-scale patterns back to microevolutionary mechanisms.