Download Molecular record Building “family” trees Artificial selection

Comparative hemoglobin structure
Molecular record
! Comparing DNA & protein structure
"
universal genetic code!
! DNA & RNA
"
Human Macaque
Why compare
these genes?
compare common genes
! cytochrome C (respiration)
! hemoglobin (gas exchange)
Human/kangaroo
Closely related species have
sequences that are more similar
than distantly related species
!! DNA & proteins are a molecular
record of evolutionary relationships
Nucleotide substitutions
100
Dog/
cow
75
Llama/
cow
Sheep/
goat
25
0
25
Lamprey
8
32 45
67
125
Human/rodent
Horse/cow
Pig/
cow
0 10 20 30 40 50 60 70 80 90 100 110 120
Goat/cow
0
Frog
Why does comparing
amino acid sequence
measure evolutionary
relationships?
Rabbit/
rodent
50 Horse/
donkey
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Human/
cow
Dog Bird
50
75
100
Millions of years ago
125
Building “family” trees
Closely related species (branches) share same line of
descent until their divergence from a common
ancestor
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Number
Number of
of amino
amino acid
acid differences
differences between
between
hemoglobin
hemoglobin (146
(146 aa)
aa) of
of vertebrate
vertebrate species
species and
and that
that of
of humans
humans
Artificial selection
! Artificial breeding can use variations in
populations to create vastly different
“breeds” & “varieties”
“descendants” of wild mustard
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“descendants” of the wolf
Artificial selection
! People have been artificially selecting
domesticated plants and animals for thousands of years.
Evidence of Natural selection in action
! Insecticide &
drug resistance
! These activities have amounted to large, long-term, practical
experiments that clearly demonstrate that species can change
dramatically through selective breeding.
"
! Shows that selection has profound effects on populations and
has the ability to modify forms and behaviors of living things to
the point that they look and act very unlike their ancestors.
"
! Artificial selection provides a model that helps us understand
natural selection.
"
"
"
! It is a small step to envision natural conditions acting
insecticide didn’t
kill all individuals
resistant survivors reproduce
resistance is inherited
insecticide becomes less & less
effective
Because the allele for insecticide
resistance spreads through the
population
! The population evolved!
selectively on populations and causing natural changes.
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Biogeographical evidence
! Biogeography: the geographic distribution of species
"
"
Influenced among other by continental drift, the slow
movement of continents over time.
Ex: Marsupial mammals are found in the Americas as well as
Australia and New Guinea.
Evidence of Evolution
by Natural Selection
! They are not found swimming across the Pacific Ocean, nor have they
been discovered wandering the Asian mainland. There appear to be
no routes of migration between the two populations.
! How could marsupials have gotten from their place of origin to
locations half a world away?
Testable Hypotheses
# Fossils of marsupials have been found in the Antarctic as well as in South
America and Australia.
# During the past few decades scientists have demonstrated that what is
now called South America was part of a large land mass called Gondwana,
which included Australia and Antarctica.
$
Gondwana split apart 160 to 90 million years ago.
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Marsupials didn't need a migration route from one
part of the world to another; they rode the
continents to their present positions.
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2006-2007
Peppered Moths
! Dark vs. light variants
Peppered moth
! What was the selection factor?
"
early 1800s = pre-industrial England
! low pollution
! lichen growing on trees = light colored bark
"
late 1800s = industrial England
! factories = soot coated trees
! killed lichen = dark colored bark
Year
1848
1895
1995
% dark
5
98
19
% light
95
2
81
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Genome sequencing
! What can data from whole
genome sequencing tell us
about evolution of humans?
"
mid 1900s = pollution controls
! clean air laws
! return of lichen = light colored bark
"
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industrial melanism
Primate Common Ancestry?
Chromosome Number in
the Great Apes
(Hominidae)
orangutan (Pogo)
gorilla (Gorilla)
chimpanzee (Pan)
human (Homo)
48
48
48
46
Could we have
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Hypothesis:
just lost a pair of
Hypothesis:
Change
Change in
in chromosome
chromosome number?
number? chromosomes?
IfIf these
these organisms
organisms share
share aa common
common
ancestor,
then
is
there
evidence
ancestor, then is there evidence in
in
the
the genome
genome for
for this
this change
change in
in
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chromosome
number
chromosome
number
Hillier et al (2005) “Generation and Annotation of the DNA
sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.
Chromosomal fusion
Test of the Human Genome
Testable
Testableprediction:
prediction:
IfIfcommon
commonancestor
ancestorhad
had48
48chromosomes
chromosomes(24
(24pairs),
pairs),
then
thenhumans
humanscarry
carryaafused
fusedchromosome
chromosome(23
(23pairs).
pairs).
Ancestral
Chromosomes
Fusion
Chromosome Number in
the Great Apes
(Hominidae)
orangutan (Pogo)
48
gorilla (Gorilla)
48
chimpanzee (Pan)
48
Testable!
human (Homo)
46
This is what makes
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evolution science
& not belief!
Ancestral
Chromosomes
Fusion
Homo sapiens
Inactivated
centromere
Telomere
sequences
Homo sapiens
Inactivated
centromere
Telomere
sequences
Chr 2
“Chromosome 2 is unique to the human
“Chromosome 2 is unique to the human
lineage of evolution, having emerged as a
lineage of evolution, having emerged as a
result of head-to-head fusion of two
result of head-to-head fusion of two
chromosomes that remained separate in
chromosomes that remained separate in
other primates. The precise fusion site has
other primates. The precise fusion site has
been located in 2q13–2q14.1, where our
been located in 2q13–2q14.1, where our
analysis confirmed the presence of multiple
analysis confirmed the presence of multiple
subtelomeric duplications to chromosomes
subtelomeric duplications to chromosomes
1, 5, 8, 9, 10, 12, 19, 21 and 22. During the
1, 5, 8, 9, 10, 12, 19, 21 and 22. During the
formation of human chromosome 2, one of
formation of human chromosome 2, one of
the two centromeres became inactivated
the two centromeres became inactivated
(2q21, whichWell
corresponds
to the centromere
I’ll
(2q21, which corresponds
to the centromere
from chimp chromosome 13) and the
from chimp
be achromosome
monkey’s 13) and the
centromeric structure quickly deterioriated.”
centromeric
quickly deterioriated.”
…or structure
an ape’s…
uncle!
Centromere
Telomere
Human
HumanChromosome
Chromosome#2
#2shows
showsthe
theexact
exact
point
at
which
this
fusion
took
place
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Biology
point at which this fusion took place
In case you had any doubts…
doubts…
"Nothing in biology
makes sense except in
the light of evolution."
-- Theodosius Dobzhansky
March 1973
Geneticist, Columbia University
(1900-1975)
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2006-2007
Don’t be a Dodo…
Evolution is "so overwhelmingly
established that it has become
irrational to call it a theory."
Ask Questions!!
-- Ernst Mayr
What Evolution Is
2001
Professor Emeritus, Evolutionary Biology
Harvard University
(1904-2005)
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2006-2007
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2006-2007