Transcript Evidence for evolution

Module 1: Evolution
Month Day Topic
Aug
Sept
28
History of life on Earth
30
Timeline construction
1
Theory of evolution
4
Holiday
6
Evidence for evolution
8
Mechanisms of evolution I
11
Mechanisms of evolution II
13
Speciation
Why did the chicken cross the road?
Evolutionist 1: It was the logical next step after coming
down from the trees.
Evolutionist 2: The fittest chickens cross the road.
Evolutionist 3: Pure chance.
Creationist: God created the chicken on the other side of
the road. There is no proof it ever was on this side.
Misconceptions
1. Evolution is a theory about the origin of life.
2. Evolution is like a climb up a ladder of progress:
organisms just keep getting better.
3. Evolution means that life changed “by chance.”
4. Natural selection involves organisms “trying” to
adapt.
5. Evolution is just a “theory”
6. Evolution is a theory in crisis and is collapsing
as scientists loose confidence in it
Misconceptions
7. Gaps in the fossil record disprove evolution
8. Evolutionary theory is incomplete and is currently
unable to give a total explanation of the changes
in life
9. The theory of evolution is flawed, but scientists
won’t admit it
10. Most biologists have rejected “Darwinism.”
11. Evolution is not science because it is not
observable or testable
Evolution has one implication:
it explains the history of life
Incorrect Implications
1. Evolution leads to immoral behavior
2. Evolution supports the idea of “might
makes right” and rationalizes the
oppression of some people by others
3. Evolution and religion are incompatible
Evidence for evolution
1.
2.
3.
4.
5.
Fossils
Biogeography
Morphology
Development
Biochemistry
1. Fossil evidence
• Recognizable evidence of ancient life
• 17th century,
association of
shark’s teeth and
“tongue stones”
• Hard body parts,
tracks, feces
Fossilization
How do we know their age?
Relative age: layering of rocks
Geologic
Time
Scale
• Boundaries
based on
transitions
in fossil
record
Phanerozoic
eon
Cenozoic
era
Quaternary period
Mesozoic
era
Cretaceous period
Tertiary period
Jurassic period
Triassic period
Paleozoic
era
Permian period
Carboniferous period
Devonian period
Silurian period
Ordovician period
Cambrian
Cambrianperiod
period
Proterozoic eon
Figure 19.4 (2)
Page 308
Archean eon and earlier
How do we know their age?
Absolute age: radiometric dating
Uranium 238—half-life of 4.5 billion years
Carbon 14—half-life of 5370 years
Radiometric Dating
parent isotope in
newly formed rock
after one half-lives
after two half-lives
Figure 19.5
Page 309
Geologic
Time
Scale
• Boundaries
based on
transitions
in fossil
record
MYA
Phanerozoic
eon
Cenozoic
era
Mesozoic
era
Quaternary period
1
Tertiary period
65
Cretaceous period
138
Jurassic period
Triassic period
Paleozoic
era
205
210
Permian period
290
Carboniferous period
370
Devonian period
Silurian period
Ordovician period
Cambrian
Cambrianperiod
period
410
435
505
570
Proterozoic eon
Figure 19.4 (2)
Page 308
Archean eon and earlier
2,500
mya
What does the fossil record
tell us?
• Lineages change over time
• Intermediate forms exist
• Most recent fossils look the most like
modern life
Why is it incomplete?
• Few organisms get buried without getting
eaten or decomposed
• Few fossils avoid erosion, lava, and other
geological events
• Few organisms live in “preservation
environments”
• Many organisms do not have hard parts
• Many fossil bearing strata have not
been exposed
2. Biogeographic evidence
• Continents were once joined and have
since “drifted” apart
• Initially based on the shapes and sutures
of land masses
• Mechanism: plate tectonics
Changing Land Masses
420 mya
260 mya
65 mya
10 mya
Figure 19.8c
Page 311
2. Biogeographic evidence
• Patterns of diversity explained by
continental position
• Continents that have been separated
longest have the most divergent floras and
faunas
• Examples: marsupials in Australia, tropical
and desert plants in South America…
3. Morphological evidence
• Homologous structures
• Guiding principle:
–When it comes to introducing change in
morphology, evolution tends to follow the path
of least resistance
Morphological
Divergence
4
5
21
3
• Change from
body form of a
common
ancestor
4
pterosaur
1
chicken
2
3
1
2
bat
3 4
• Produces
homologous
structures
Figure 19.10
Page 312
3
early
reptile
21
1
5
porpoise
2
4
3
5
penguin
2
1
2
3
4
5
3
human
4. Developmental evidence
• Each animal or plant proceeds through a
series of changes in form
• Similarities in these stages may be clues
to evolutionary relationships
• Mutations that disrupt a key stage of
development are selected against
Altering Developmental
Programs
• Some mutations shift a step in a
way that natural selection favors
• Small changes at key steps may bring
about major differences
• Insertion of transposons or gene mutations
Similar Vertebrate Embryos
• Alterations that disrupted early development
have been selected against
FISH
REPTILE
BIRD
MAMMAL
Figure 19.13a
Page 315
Developmental Changes
• Changes in the onset, rate, or time of
completion of development steps can
cause changes in form
• Ex: Adult forms that retain juvenile features
Proportional Changes in Skull
Chimpanzee
Human
Figure 19.14b
Page 315
5. Biochemical evidence
• Kinds and numbers of biochemical traits
that species share is a clue to how closely
they are related
• Can compare DNA, RNA, or proteins
• More similarity means species are more
closely related
Comparing Proteins
• Compare amino acid sequence of proteins
produced by the same gene
• Human cytochrome c (a protein)
–Identical amino acids in chimpanzee protein
–Chicken protein differs by 18 amino acids
–Yeast protein differs by 56
Sequence Conservation
• Cytochrome c functions in electron
transport
• Deficits in this vital protein would be
lethal
• Long sequences are identical in wheat,
yeast, and a primate
Sequence Conservation
Yeast
Wheat
Primate
Figure 19.15
Page 316-317