Natural Selection, Evolution, and Ecology

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Transcript Natural Selection, Evolution, and Ecology

Natural Selection, Evolution,
and Evolutionary Ecology
Dr. James Danoff-Burg
Columbia University
Levels of Ecological
– Evolutionary influences
– Human influences
– Abiotic changes
– Biotic interactions
Most ecologists explore the last three levels
Progress of Ecological Inquiry?
 Explore
 If
 If
plausible ultimate answers
one is supported, stop
no ultimate answers are supported,
explore proximate answers
 Need
to pitch the question at the right
 Example
– Why are Penguins only in the Southern
– Proximate - insufficient food, too many
predators, lack of shelter, etc.
– Ultimate - historical and thus evolutionary
distribution --> favored at present
Two EvolEcol Branches
 Intraspecific
– Relative selective value of different traits
– Origin of intraspecific diversity
 Interspecific
– Behavioral ecology (comparative studies)
– Systematics and phylogeny
Common feature of all branches - Evolution!
 Change
through time within a lineage
 Mechanisms / Producers of Variation
– Genetic drift
– Phenotypic plasticity
– Natural Selection
Natural Selection  Evolution
Natural Selection
 Proposed
by Darwin and Wallace
 Evolutionary mechanism
 One way that variation exists and is
maintained in a population
 Value is relative to local competitors
 Only a negative action
– Only selection AGAINST a form of a trait
– Never selection for a trait
Intraspecific Variation
 Possible
– Genetic drift
– Phenotypic plasticity
– Natural Selection
 How
to differentiate between them?
– Genetic fixation / continuity through lineages
– Use traits that do not change in response to
changes in environment
Today’s Activity
How do changes in a resource gradient affect
intraspecific diversity?
– Are these changes due to natural selection?
Choose an organism with the following
Low vagility
Does not disperse aerially
Clearly marked adult stage
Traits under study do not change
Activity Tasks
Plan activity
 Collect data and enter into eBiome
 Analyze our data
 Wait for data from other sites
 Jointly analyze all data
 Make conclusions about relationship
 Posit future studies to distinguish between
evolutionary mechanisms
Planning - To be Determined:
 Environmental
 Experimental organism
 Organismal trait for study
 Statistical technique to use, justify