Download Lecture 2-Evidence for Evolution

Evidence for
Evolution
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KEY CONCEPT
•
New life forms evolved from early life
forms.
•
Are there evidence to show common
ancestry among species?
•
Yes…. Evidence from many
sources?
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Evidence supporting evolution
 Fossil Evidence

shows change over time
 Anatomical Evidence

comparing body structures
 homology & vestigial structures
 embryology & development
 Molecular Evidence

comparing protein & DNA
sequences
 Artificial selection
human caused evolution

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1. Fossil record
 Layers of rock contain fossils

new layers cover older ones
 creates a record
over time
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Fossils tell a story…
the Earth is old
Life is old
Life on Earth has changed
Fossils show complex life forms have evolved
from simpler life forms
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Eg. Evolution of birds
Today’s birds
descended from
ancestral birds
Fossil of Archaeopteryx
 lived about 150 mya
 links reptiles & birds
Extinct Fossils
resemble modern
animals. This shows a
common ancestry.
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2. Anatomical records
Animals with different
structures on the surface
But when you look under
the skin…
It tells an evolutionary story
of common ancestors
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Compare the bones
 The same bones
under the skin
 limbs that
perform
different
functions are
built from the
same bones
How could these
very different animals
have the
same bones?
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Homologous structures
 Structures that come from the same origin
 homo- = same
 -logous = information
 Forelimbs of human, cats, whales, & bats





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same structure
 on the inside
same development in embryo
different functions
 on the outside
Homologous structures are evidence of a
common ancestor.
But don’t be fooled by these…
 Analogous structures

look similar
 on the outside
same function
 different structure & development

 on the inside
different origin
 no evolutionary relationship

Solving a similar problem with a similar solution
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Analogous structures
 Dolphins: aquatic mammal
 Fish: aquatic vertebrate
both adapted to
life in the sea
 not closely related

Watch the tail!
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Convergent evolution
 3 groups with wings

Does this mean they have a
recent common ancestor?
They just
came up
with the
NO!
same answer!
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Flight evolved 3
separate times —
evolving similar
solutions to similar
“problems”
Vestigial organs
 Hind leg bones on whale fossils
Why would whales
have pelvis & leg
bones if they were
always sea creatures?
Because they
used to
walk on land!
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Comparative embryology

Similar embryos suggest common ancestry
among animals
All vertebrate embryos have a “gill
pouch” at one stage of development
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4. Molecular record
 Comparing DNA & protein structure

everyone uses the same genetic code!
 DNA
Human
Macaque
Dog Bird
Frog
Lamprey
8
32 45
67
125
 compare common genes
 compare common proteins
number of amino acids different
from human hemoglobin
0 10 20 30 40 50 60 70 80 90 100 110 120
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Building “family” trees
Closely related species are branches on the tree —
coming from a common ancestor
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5. Artificial selection
 How do we know natural selection can
change a population?
we can recreate a similar process
 “evolution by human selection”
“descendants” of wild mustard

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Selective Breeding
Humans create the
change over time
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“descendants”
of the wolf
Artificial Selection
…and the
examples
keep coming!
I liked
breeding
pigeons!
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Artificial Selection gone bad!
 Unexpected
consequences of
artificial selection
Pesticide resistance
Antibiotic resistance
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Now the biggest
Q
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Evolution or Creation
?????
Some - believe in Evolution
Some others - believe in creation
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 The Monkey Trial
In 1925, the Tennessee legislature passed
the BUTLER LAW.
Forbade the teaching of Darwin's theory of
evolution in any public school or university.
inTennessee, USA.
Penalties to teachers 100 dollars.
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Kelly Segraves v. California State trial in 1981.
Kelly Segraves, parent of three schoolchildren, sued
the State of California, for teaching of evolutionary
biology in public schools.
He argued that it violated the Free Exercise Clause of
the First Amendment to the US Constitution by teaching
evolution.
The judge found that California's anti-dogmatism policy
gave sufficient accommodation to the views of
Segraves.
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Any Questions??
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