Transcript Chapter 23. - Net Start Class

Chapter 21.
Evidence of Evolution
by Natural Selection
Dodo bird
Evolution is "so overwhelmingly
established that it has become
irrational to call it a theory."
-- Ernst Mayr
What Evolution Is
2001
Professor Emeritus, Evolutionary Biology
Harvard University
(1904-2005)
Support for Darwin’s ideas
 Fossil
_______________
Record
change over time
Comparative
Anatomy
___________________


Homologous structures
 Analogous structures
 embryology

Analysis
 Molecular
_________________

measure of common
ancestry
Artificial Selection
 ________________

induced evolution
Fossil record
 Layers of sedimentary rock contain fossils
new layers cover older ones, creating a
record over time
 fossils within layers show that a
succession of organisms have populated
Earth throughout a long period of time

Formation of sedimentary strata
containing fossils
1 Rivers carry sediment to the
ocean. Sedimentary rock layers
containing fossils form on the
ocean floor.
2 Over time, new strata are
deposited, containing fossils
from each time period.
3 As sea levels change and the seafloor
is pushed upward, sedimentary rocks are
exposed. Erosion reveals strata and fossils.
Younger stratum
with more recent
fossils
Older stratum
with older fossils
A gallery of fossil types
(c) Leaf fossil, about 40 million years old
(b) Petrified tree in Arizona, about
190 million years old
(a) Dinosaur bones being excavated
from sandstone
(d) Casts of ammonites,
about 375 million
years old
(f) Insects
preserved
whole in
amber
(g) Tusks of a 23,000-year-old mammoth,
frozen whole in Siberian ice
(e) Boy standing in a 150-million-year-old
dinosaur track in Colorado
Fossil record
 Today’s organisms descended from
ancestral species
 Support for a very old earth
A dragonfly fossil from Brazil, more than
100 million years old
Evolution of birds
 Archaeopteryx


lived about 150 mya
links reptiles & birds
Smithsonian Museum,
Washington, DC
Evolutionary Change in Horses
Land Mammal
?
?
?
?
A transitional fossil linking past and
present
2006 Fossil Discovery of Early Tetrapod
 Tiktaalik

“missing link” from sea to land animals
Burgess Shale
Burgess Shale
 British Columbia
 505 million years ago (Cambrian


Explosion)
Period when animals rapidly diversified
in body plan/anatomical feature
Taphonomic window
_________________
Anatomical record
 Homologous structures

similarities in characteristics resulting
from _______________
common ancestry
Homologous structures
structure
 Similar _________
development
 Similar ____________
functions
 Different _________
 Evidence of close
evolutionary
relationship

recent common
_______
ancestor
Homologous structures
spines
leaves
succulent leaves
needles
colored leaves
tendrils
Analogous structures
 Separate evolution of structures
structure
similar ____________
external form
 similar ________________
 different
_____________ internal structure &
development
origin
 different_________


no ______________________
evolutionary relationship
Don’t be fooled
by their looks!
Solving a similar problem with a similar solution
Analogous structures
 3 groups with wings

does this mean they have a
recent common ancestor?
flight evolved 3
separate times =
evolving similar
solutions to similar
“problems”
Convergent evolution
 Fish: aquatic vertebrates
 Dolphins: aquatic mammals
similar adaptations to
life in ______
similar environments
 not closely related

Those fins & tails
& sleek bodies are
analogous structures!
Parallel Evolution
 Convergent evolution in common niches


Similar ecological roles in ________environments,
different
Similar adaptations were selected
but are not closely related
marsupial
mammals
placental
mammals
Convergent evolution of analogous burrowing
characteristics
marsupial mole
placental mole
Parallel types across continents
Niche
Burrower
Placental Mammals
Australian Marsupials
Mole
Marsupial mole
Anteater
Numbat
Anteater
Nocturnal
insectivore
Mouse
Climber
Marsupial mouse
Spotted cuscus
Lemur
Glider
Stalking
predator
Chasing
predator
Sugar glider
Flying
squirrel
Ocelot
Tasmanian cat
Wolf
Tasmanian “wolf”
Vestigial organs
little or no functions
 Structures that serve _________________
remnants of structures that were
functional in ancestral species
 deleterious mutations accumulate in genes
for non-critical structures without reducing
fitness
 snakes & whales — remains of pelvis &
leg bones of walking ancestors
 eyes on blind cave fish
 human tail bone

Vestigial organs
 Hind leg bones on whale fossils
Why would whales
have pelvis & leg bones
if they were always
sea creatures?
Comparative embryology
 Similar embryological development in
closely related species

all vertebrate embryos have similar
structures at different stages of
development
 gill pouch in fish, frog, snake, birds, human,
etc.
Anatomical similarities in vertebrate embryos
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Human embryo
Molecular record
 Comparing DNA & protein structure

universal genetic code!
 DNA & RNA

Why compare
these genes?
compare common genes
 cytochrome C (respiration)
 hemoglobin (gas exchange)
Human/kangaroo
100
 A molecular record of evolutionary
relationships
75
Rabbit/
rodent
50 Horse/
donkey
Sheep/
goat
25
Nucleotide
substitutions
Closely related species have
sequences that are more similar
than distantly related species
Dog/
cow
Human/
cow
Human/rodent
Llama/
cow
Horse/cow
Pig/
cow
Goat/cow
0
0
25
50
75
Millions of years ago
100
125
Comparison of a protein found in
diverse vertebrates
Species
Percent of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
100%
Human
Rhesus monkey
95%
Mouse
87%
Chicken
69%
Frog
Lamprey
54%
14%
Comparative hemoglobin structure
Human Macaque
Dog Bird
Frog
Lamprey
32 45
67
125
Why does comparing
amino acid sequence
measure evolutionary
relationships?
8
0 10 20 30 40 50 60 70 80 90 100 110 120
Number of amino acid differences between
hemoglobin (146 aa) of vertebrate species and that of humans
Building “family” trees
Closely related species (branches) share same line of
descent until their divergence from a common ancestor
Artificial selection
 Artificial breeding can use variations in
populations to create vastly different
“________”
varieties
breeds & “__________”
“descendants” of wild mustard
“descendants” of the wolf
Natural selection in action
 Insecticide &
drug resistance
 insecticide doesn’t
kill all individuals
 resistant survivors
reproduce
 resistance is inherited
 insecticide becomes
less & less effective
Evolution of drug resistance in HIV
Patient
No. 1
Patient No. 2
Patient No. 3
Weeks
Evolution Misconceptions
Evolution is not goal-oriented
An evolutionary trend does not mean that
evolution is goal-oriented.
Surviving species
do not represent
the peak of
perfection. There
is compromise &
random chance
involved as well
Remember that for
humans as well!
Evolution is not the
survival of the fittest.
Rather it is the
survival of the just
good enough.
"Nothing in biology
makes sense except in
the light of evolution."
-- Theodosius Dobzhansky
March 1973
Geneticist, Columbia University
(1900-1975)
I might be dead, but
Perhaps you children
would appreciate a bit of
what you call the “rap”
music?!?
Just Because Things Seem Obvious
Doesn’t Mean They Don’t Need To Be Supported
Peppered Moths
 Dark vs. light variants
Year
1848
1895
1995
% dark
5
98
19
% light
95
2
81
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

mid 1900s = pollution controls
 clean air laws
 return of lichen = light colored bark

industrial melanism
Genome sequencing
 What can whole genome
sequence data tell us about
evolution of humans?
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
just lost a pair of
chromosomes?
Hypothesis:
Change in chromosome number?
If these organisms share a common
ancestor, then is there evidence in
the genome for this change in
chromosome number
Chromosomal fusion
Testable prediction:
If common ancestor had 48 chromosomes (24 pairs),
then humans carry a fused chromosome (23 pairs).
Ancestral
Chromosomes
Fusion
Chromosome Number in
the Great Apes
(Hominidae)
Inactivated
centromere
Telomere
sequences
orangutan (Pogo)
48
gorilla (Gorilla)
48
chimpanzee (Pan)
48
Testable!
human (Homo)
46
This is what makes
evolution science
& not belief!
Homo sapiens
Centromere
Telomere
Hillier et al (2005) “Generation and Annotation of the DNA
sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.
Test of the Human Genome
Ancestral
Chromosomes
Fusion
Homo sapiens
Inactivated
centromere
Telomere
sequences
Chr 2
“Chromosome 2 is unique to the human
lineage of evolution, having emerged as a
result of head-to-head fusion of two
chromosomes that remained separate in
other primates. The precise fusion site has
been located in 2q13–2q14.1, where our
analysis confirmed the presence of multiple
subtelomeric duplications to chromosomes
1, 5, 8, 9, 10, 12, 19, 21 and 22. During the
formation of human chromosome 2, one of
the two centromeres became inactivated
(2q21, whichWell
corresponds
to the centromere
I’ll
from chimp chromosome 13) and the
be a monkey’s
centromeric structure quickly deterioriated.”
…or an ape’s…
uncle!
Human Chromosome #2 shows the exact
point at which this fusion took place
Geographic variation in chromosomal
mutations
1
2.4
3.14
5.18
8.11
9.12
10.16
13.17
1
2.19
3.8
4.16
9.10
11.12
13.17
15.18
6
7.15
19
XX
5.14
6.7
XX
Unity & Diversity
 Only evolution explains both the unity
& diversity of life
 By attributing the diversity of life to
natural causes rather than to
supernatural creation, Darwin gave
biology a strong, scientific, testable
foundation
Any Questions??
2007-2008
1. A complete fossil record
A. Exists because of the great preservation in
B.
C.
D.
E.
ocean sediment
Exists because of the solidification of
minerals around organisms
Is available because of the small location
in which all organisms used to live
Exists because organisms that die become
embedded in the soil to form rocks
Does not exist
2. The similarity of insect wings and bird
wings is an example of
A. Behavioral adaptations
B. Geographic isolation
C. Adaptive radiation
D. Convergent evolution
E. Divergent evolution
3. The human appendix is an example of
A. A balanced polymorphism
B. Divergent evolution
C. Convergent evolution
D. A vestigial structure
E. A homologous structure
One piece of evidence that supports
evolution from molecular biology is:
A. carbohydrate structure
B. amino acid sequence
C. lipid composition
D. nucleotide structure
E. cellulose chains
Any Questions??