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Evidence for Evolution
(Is there a Pattern of Change?)
Scientific Method
Make Observation
Formulate hypothesis to
explain observation
Pass
Test Hypothesis
Hypothesis
Pass
Fail
Theory
Test Theory
Fail
Pass Many
Theory
Law
Fail
Can we recognize changes in populations over
time?
1. Smaller scale changes in populations Biston betularia - peppered moth
Peppered moth comes in two
genetic types (or morphs)
1.
2.
Dark
Light
Each morph has an advantage over
the other depending on the kind of
background on which they are found.
They are harder to find by predators if
they are on a compatible background.
Industrial Pollution in England
Smoke from factories
darkened tree trunks
And made the dark morph
more difficult to see
But the level of industrial smoke has been declining
300
Level of
smoke
(g/m3
0
1960
1970
1980
As has the frequency of the dark morph
300
100
Percent of the
dark morph in the
population
Level of
smoke
(g/m3
0
0
1960
1970
1980
1.
Smaller scale changes in populations - House sparrows
(Passer domesticus)
1.
Smaller scale changes in populations - House sparrows
(Passer domesticus)
Vancouver (1900)
Death Valley
(1914)
1852
Mexico City (1933)
Costa Rica (1974)
1.
Smaller scale changes in populations - House sparrows
(Passer domesticus)
83
Edmonton
81
Lawrence, Kansas
Death Valley
Wing
Length
(mm)
79
77
75
Death
Valley
Lawrence,
Kansas
Edmonton
1. Smaller scale changes in populations - Lab Experiments
Drosophila - Fruit fly
Researchers allow two species of fruit flies to coexist in the lab.
Drosophila simulans
Drosophila melanogaster
These flies are competing for food
Hypothesis:
Poorer competitors will be those that produced fewer
offspring and the average number of offspring/female should
increase over time.
D. melanogaster
D. simulans
Number of
offspring/female
0
At start of experiment
Hypothesis:
Poorer competitors will be those that produced fewer
offspring and the average number of offspring/female should
increase over time.
D. melanogaster
D. simulans
Number of
offspring/female
0
At start of experiment
26 generations later
1. Smaller scale changes in populations - Ring Species
Herring Gull
Herring Gull
1. Smaller scale changes in populations - Ring Species
Vega Gull
Herring Gull
Herring Gull
1. Smaller scale changes in populations - Ring Species
Vega Gull
Birula
Gull
Herring Gull
Herring Gull
1. Smaller scale changes in populations - Ring Species
Vega Gull
Birula
Gull
Herring Gull
Herring Gull
Heuglin’s
Gull
1. Smaller scale changes in populations - Ring Species
Vega Gull
Birula
Gull
Herring Gull
Herring Gull
Heuglin’s
Gull
Lesser Black
Back Gull
Ring Species - Ensatina
Original species
2. Larger Scale Evolution - Homologies
Homology - similarity in characteristics resulting from
shared ancestry.
2. Larger Scale Evolution - Homologies
Why 5 digits on all tetrapod limbs?
As opposed to analogous structures which resemble each other because of
similar function.
Shark
Human
Whale
e.g. fins
Octopus
e.g. eyes
2. Larger Scale Evolution - Homologies
DNA
RNA
This code is universal
in all life
Protein
(chains of amino acids)
Each amino acid
has a triplet
chemical code
U - uracil
G - guanine
A - adenine
C - cytosine
2. Larger Scale Evolution - Homologies
Brush rabbit
E. coli
RNA rabbit hemoglobin
Rabbit hemoglobin
Definition of Evolution
Changes over time of the proportion of individuals
differing genetically in one or more traits
These changes can occur by:
• Changes in frequency of alleles and/or phenotypes in a
population
• Changes in the proportion of different populations in a species
• Changes in the number of species in a larger taxonomic group
Definition of Evolution
Evolution is the pattern of change over time.