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Natural Selection, Speciation,

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Know & apply types of natural selection. Know & apply examples of natural selection ... Example: Stickleback fish. Over time, sticklebacks in lakes typically evolve ... – PowerPoint PPT presentation

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Title: Natural Selection, Speciation,


1
Natural Selection, Speciation, Extinction
  • April 2009

2
Major Goals
  • Understand process of natural selection
  • Vocab (n.s., fitness, adaptation)
  • Know apply types of natural selection
  • Know apply examples of natural selection

3
Darwins Role
  • Who was the first person to
  • propose a theory of evolution?

4
Darwins Role
  • Who was the first person to
  • propose a theory of evolution?
  • Lucretius (100-50 BC)

5
Darwins Role
  • Who was the first person to
  • propose a theory of evolution?
  • Lucretius (100-50 BC)
  • Darwin was the first to
  • propose a mechanism of
  • speciation that is
  • still accepted today ….
  • Natural Selection

6
Natural Selection
  • Darwin made 4 observations that led
  • to his theory
  • Resources are limited

7
Natural Selection
  • Darwin made 4 observations that led
  • to his theory
  • Resources are limited
  • Not all individuals survive reproduce

8
Natural Selection
  • Darwin made 4 observations that led
  • to his theory
  • Resources are limited
  • Not all individuals survive reproduce
  • Physical characteristics vary

9
Natural Selection
  • Darwin made 4 observations that led
  • to his theory
  • Resources are limited
  • Not all individuals survive reproduce
  • Physical characteristics vary
  • Many physical characteristics are heritable

10
Natural selection
  • Beneficial traits
  • More offspring


11
Natural selection
  • Beneficial traits
  • More offspring
  • If beneficial traits are
  • heritable
  • More beneficial traits in
  • population


12
Natural selection
13
Natural selection
  • Fitness describes an organisms genetic
    contribution to future generations relative to
    other individuals.
  • More offspring usually greater fitness

14
Example Peppered Moths
  • Before 1850, peppered
  • moths light colored

15
Example Peppered Moths
  • Before 1850, peppered
  • moths light colored
  • During Industrial Revolution,
  • trees moths darkened

16
Example Peppered Moths
  • Before 1850, peppered
  • moths light colored
  • During Industrial Revolution,
  • trees moths darkened
  • As pollution cleared, light
  • moths returned

17
Example Peppered Moths
  • Before 1850, peppered
  • moths light colored
  • During Industrial Revolution,
  • trees moths darkened
  • As pollution cleared, light
  • moths returned
  • How would this happen?

18
Example Peppered Moths
  • Before 1850, peppered
  • moths light colored
  • During Industrial Revolution,
  • trees moths darkened
  • As pollution cleared, light
  • moths returned
  • Seen with several species, in several countries!

19
Example Peppered Moths
20
Example Peppered Moths
  • Selection is the only mechanism to produce
    adaptation -- traits that enable an organism to
    better survive and reproduce.
  • In peppered moths, color patterns that match the
    background is an adaptation that reduces
    predation.

21
Types of selection
  • Stabilizing Average trait is favored
  • Example Human birth weight

22
Types of selection
  • Directional One extreme is favored
  • Example Less colorful guppies favored
  • when visual predators are present.

23
Types of selection
  • Disruptive Both extremes are favored
  • Example Small beaks best for soft seeds large
    beaks best for hard seeds.

24
Effects of Natural Selection
  • Natural selection can …
  • change physical traits
  • Example Galapagos Finches

25
Effects of Natural Selection
  • Natural selection can …
  • change physical traits
  • Example Galapagos Finches

26
Effects of Natural Selection
  • Natural selection can …
  • change behavioral traits
  • Example Rattlesnakes in TX and OK

27
Effects of Natural Selection
  • Natural selection can …
  • increase diversity
  • Example Adaptive radiations on islands

28
Effects of Natural Selection
  • Natural selection can …
  • lead to speciation
  • Example Stickleback fish
  • Over time, sticklebacks in lakes typically evolve
  • into two forms to utilize two environments
  • bottom of the lake (benthic) and top of the lake
  • (limnetic)

29
Effects of Natural Selection
  • Natural selection can …
  • reduce (but not stop) extinction

30
Effects of Natural Selection
  • Natural selection can …
  • reduce (but not stop) extinction
  • WHY?

31
Effects of Natural Selection
  • Natural selection can …
  • reduce (but not stop) extinction
  • WHY?
  • Natural selection can only act on existing
    variation. As G.C. Williams put it
  • The imminence of extinction does not evoke
    emergency measures on the part of the population
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