Natural Selection Darwin was the first to introduce the idea that… Evolution, the changes within a population, took place through a process called Natural Selection Natural Selection Organisms best adapted to their environment are more likely to survive and reproduce, passing those beneficial traits on to their offspring.
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Natural Selection
Darwin was the first to introduce the idea that…
Evolution, the changes within a population, took place through a process called Natural Selection
Natural Selection
Organisms best adapted to their environment are more likely to survive and reproduce, passing those beneficial traits on to their offspring.
Natural Selection
How does natural selection lead to change? What does this look like? Let’s imagine…
There is a population of beetles with variation in
color
A drought causes the ground and trees to
become brown, meaning green beetles are more easily seen and eaten!
Brown beetles are more
camouflaged and therefore
survive and reproduce
After many generations, the
population of beetles is
entirely brown
Natural Selection
Natural Selection explains many amazing creatures!
Venomous coral snake vs. scarlet king snake [ MIMICRY ]
Rot-Hole Tree Frog lives on moss covered trees [CAMOUFLAGE]
Harmless! Deadly!
Natural Selection
Natural Selection can change a population in several ways:
Directional Selection
Disruptive Selection
Stabilizing Selection
Natural Selection
Directional Selection: selection towards a single direction.
Stabilizing Selection: selection towards the mean. Selection against the extremes.
Disruptive Selection: selection against the mean. Selection towards the extremes.
Natural Selection – Directional Selection
Natural Selection – Directional Selection
An original population of beetles is about 50% light green and 50% dark green.
What happens if the beetle population moves into a new environment with dark soil and vegetation?
Natural Selection – Stabilizing Selection
Natural Selection – Stabilizing Selection
An original population of beetles is about 50% light green and 50% dark green.
What happens if the beetle population moves into a new environment covered in medium-green colored ferns?
Natural Selection – Disruptive Selection
Natural Selection – Disruptive Selection
An original population of beetles is about 50% light green and 50% dark green.
What happens if the beetle population moves into a new environment covered in both light-green moss and dark green shrubs?
Natural Selection - Speciation
Can the process of natural selection cause enough changes to accumulate that a new species develops?
How do you know if this has happened???
Speciation: the formation of a new species through evolution
Natural Selection - Speciation
Natural Selection - Speciation
The interaction of a population with environmental changes can lead to different rates of speciation
Rate of Speciation Theories:
Gradualism
Punctuated Equilibrium
Natural Selection - Speciation
Gradualism Model
Species diverge slowly
Change occurs in small steps
Typically occurs in:
Large populations
Stable environments
Natural Selection - Speciation
Punctuated Equilibrium Model
Species diverge rapidly
Change occurs in bursts
Long periods of no change
Typically occurs in:
Small populations
Rapidly changing environments
Natural Selection - Speciation
Natural Selection – Patterns of Evolution
Evolution can follow several different patterns, depending on pressures in the environment
Patterns of Evolution:
Divergent Evolution
Convergent Evolution
Coevolution
Divergent Evolution
Convergent Evolution
Coevolution
Natural Selection – Patterns of Evolution
Divergent Evolution –Related species becoming more and more different due to living in differentenvironments
Darwin’s Finches!
Natural Selection – Patterns of Evolution
Divergent Evolution –
Explains the formation of homologous structures
Suggests a recent common ancestor
Natural Selection – Patterns of Evolution
Convergent Evolution – Unrelatedspecies becoming more and more similar due to living in similarenvironments, even if living across the world from one another!
Antifreeze proteins in Arctic and Antarctic fish!
The antifreeze proteins in these fish are very different, suggesting that they evolved separately from one another
Natural Selection – Patterns of Evolution
Convergent Evolution –
Explains the formation of analogous structures
Do NOT share a recent common ancestor
Natural Selection – Patterns of Evolution
Coevolution– The simultaneous evolution of two unrelated species due to their close interaction/relationship
The bats and flowers of tropical regions!
Bats – Long, slender muzzlesFlowers – Light color and fruity odor
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