EVOLUTION CONTINUED
“Where’s the Evidence?!”
Chap. 13 The Macroevolutionary
Puzzle
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109 paleontologist
vestigial structure
homologous structure
gradualism
punctuated equilibrium
continental drift
analogous character
isotope
117 radioisotope
Vocabulary
Read
(282-292)
(740)(327)
Radiometric Dating or
Radioactive Dating
• Isotope- 1 form that an element can
have. Number of neutrons is variable
between isotopes of the same
element. (number of electrons and
protons stays the same)
• Minerals possess radioactive isotopes
(give off energy and subatomic
particles) that decay (breakdown) into
smaller isotopes.
• Formed in igneous rock, the minerals
grow as the liquid rock cools.
• Amounts of the “parent” (or original)
and “daughter” isotopes can be
measured in a sample collected
today.
• The rate of decay can be calculated
experimentally.
• “Half Life” is a common unit of
measure of the rate of break down.
Radioactive
parent nucleus
pp
p
p
p
p
Decay process
Daughter
nucleus
pp
pp
p
p
Proton
Neutron
p
(a) Alpha decay
pp
p
p
p
p
Atomic mass decreases
by 4; atomic number
decreases by 2
p
p
pp
p
p
p
p
Alpha particle
Emission of 2 protons and 2
neutrons (alpha particle)
pp
p
p
p p p
Atomic mass not changed
much; atomic number
increases by 1 because
Neutron becomes proton
Beta particle
(b) Beta decay
An electron (beta particle) is
ejected from the nucleus
pp
p
p
p
p
p
pp
p
p
p
p
p
Beta particle
(c) Electron capture
pp
p
p
p
p
Atomic mass not
changed much;
atomic number
decreases by 1
electron combines with a proton
to form a neutron
Sample Problems
• The half-life of Potassium 40 is 1.3 million
years. It breaks down into Argon 40
• 1) If an original rock sample contains 200
micrograms of Potassium 40, how much
would remain after two half-lives?
Uranium 238 has a half-life of 4.51
billion years and decays into Lead 206
• 2) A newly discovered rock sample has 15
micrograms of Uranium 238 and 105
micrograms of the daughter material Lead
206. How old is this rock?
Homework 2 sides in binder
• The next 2 slides are more practice
problems to work on later.
– U238 decays into Pb206 in 4.51 billion years
(HALF LIFE)
– How much U238 and Pb206 are present in a
sample after 2 HALF LIVES?
– (original sample is 300 grams)
– U238 75 grams
Pb206
225 grams
– How long would 2 half lives be?
– 9.02 billion years
– How old is an igneous rock sample containing
275g U238 and 1925g Pb206?
– 3 x 4.51 = 13.53 billion years
V. EVIDENCE OF EVOLUTION
FROM FOSSILS
“any evidence of once living creatures”
Where are fossils most likely to be
found?
A. 4 Types of Fossils
• 1. Compression- organic material
between layers of sediment, Some details
can be observed . ex. fern frond, fish
• 2. Impression- external shape and form,
no organic matter ex. foot print, limb print
• 3. Mold and cast- external features in one
layer, then the item itself is replaced by
other sediments
ex. Egg, shark tooth
• 4. Petrifaction- tissues are gradually
infiltrated by minerals. No organic material
remains
ex. petrified wood
How impression fossils form (the most common type)
8_10
Shells
settle on
ocean
floor
Cast forms when mold
is filled in with mineral
water
Rock broken
to reveal
fossil cast
Shells
buried in
sediment
Mold, or cavity,
forms when original
shell material
is dissolved
Rock broken
to reveal external mold
of shell
BOG people
• Bogs filled with danger where you could
easily get lost and drown. It's not hard to
understand why tribes of long ago used to
believe that gods and ghosts inhabited the
swamps. Gifts and sacrifices were thought
to win their good graces. Prehistoric man
offered all kinds of objects to the bogs. So
it was that bogs became gigantic offering
locations.
• Never before had there been so many bog
bodies and offering all in one place.
Schatten uit het veen provides an
impressive picture of the beliefs and rituals
of our ancestors in North-western Europe.
B. Distribution of fossils in layers of rocks?
many varieties
and great complexity
first fossils were
aquatic and some
are extinct
few varieties
and little complexity
YOUNGEST
Fossils in every layer
OLDEST
STRATIFICATION
Each geologic time period is
characterized by certain fossils
(remember the GEO TIME TABLE?)
Why do organisms disappear from
the fossil record?
• 1. unable to adapt to a changing
environment
• Ex. lake drying, cooling climate ,glaciers
• 2. out competed by organisms more
suitable to the new environment
• Ex. reptiles competing with early mammals
• Or fish vs. amminoids
Diagram of species abundance
over time
• Flowering
plants and
ferns
Diagram of species abundance
over time
• Bony fish and
amminoids
Notes in student binder
• GREAT! Less writing
VI CONTINENTAL DRIFT or
PLATE TECTONICS
• Alfred Wegener early 20th century
• initially incorrect explanation but
modified theory is widely accepted
(seafloor stationary
and continents
move WRONG!!!!)
• 10 MAJOR PLATES AND MANY MINOR
PLATES UP TO 100 KM THICK
• Continents ride on the moving crustal
plates (less dense material )
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These are the possible events at
the boundary of plates
• Slide
• Spread
These are the possible events at
the boundary of plates
• Subduction
• Subduction w/continents
1. Theory and Evidence
• OLD
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1. puzzle pieces
2. fossil distribution
3. sediment layers "Gandwanan
Sequence" similar geology on the 4
southern continents
sandstone with coal
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black shale
glacial till
NEW
• 1. earthquake distribution
• shallow quakes at ridges
Mid Atlantic
• shallow and deep quakes at trenches
subduction
• distribution of the RING OF FIRE pg 303
2. Movement of plates can be measured
from space
3. Dating rocks on opposite sides of ridges
Draw ring of fire on map
End of geological evidence
• * the earth is old and has changed
(volcanoes, glaciers, earthquakes)
• * organisms that lived in the past are
now gone
• * different organism appear in later
rocks than in early ones
• therefore new organisms must be
developing from old EVOLUTION
VII EVIDENCE OF EVOLUTION
FROM LIVING CREATURES
• Common Ancestry through comparative
anatomy
• Georges Buffon 1760 French Naturalist
• - observed the feet and legs of many
animals
• - concluded that they were but variations
on a single theme
• "The ancestors of backboned
animals must have had the same
limb structure but has been
modified for the life of the
individual"
• *This suggests that organisms
have changed with time and had
a distant common ancestor **
What similarities must exist for organisms
to have a common ancestor?
• 1. anatomy (talons, bones, coloration)
• 2. physiology (DNA, hemoglobin, digestion)
• 3. behavior ( instinct, learning)
Evidence of Evolution from living
creatures continued
• HOMOLOGOUS STRUCTURES- organs
or parts that are structurally similar but
may have different functions (Indicates
common ancestry or origin) SEE
HANDOUT
• ANALOGOUS STRUCTURES- same
function but structurally different (bird and
moth wing) Does not indicate any
relatedness SEE HANDOUT
• VESTIGIAL ORGANS- remnants of organs
or parts that are believed to have been
well developed in ancestors but have little
function now. (genes are still present)
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(tailbone, appendix, pelvic bones, )
SEE HANDOUT
Vestigial organs
• Modern animals may have structures
that serve little or no function
– remnants of structures that were functional
in ancestral species
– evidence of change over time
• some snakes & whales show remains of the
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?
• BIOCHEMICAL- organic compounds that
are essential to certain processes
• (blood proteins, cytochrome C universal
and essential to aerobic respiration, DNA ,
ribosomes) SEE LAB ACTIVITY
Molecular biology
• Comparing DNA & protein structure
– universal genetic code!
• DNA & RNA
– cytochrome C (respiration)
• protein structure
– hemoglobin (gas exchange)
• protein structure
Evolutionary relationships among species are documented
in their DNA & proteins.
Closely related species have sequences that are more
similar than distantly related species.
Before comparing the amino acids
Hypothesize on closely related pairs
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Pair
1.
2.
3.
Reason
Before comparing the amino acids
Hypothesize on unrelated pairs
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Pair
1.
2.
3.
Reason
• EMBRYOLOGICAL- the study of early
developmental forms between organisms
can suggest relatedness. (ex. larva forms
may look similar though the adults do not)
SEE HANDOUT
Comparative embryology
• Similar embryological development in
closely related species
– all vertebrate embryos have a gill pouch at
one stage of development
• fish, frog, snake, birds, human, etc.
Building “family” trees
Closely related species (twigs of tree) share same
line of descent until their recent divergence from a
common ancestor
PATTERNS OF EVOLUTION
• MORPOLOGICAL DIVERGENCE related
organisms become less similar due to different
environmental circumstances . Develop features
to suit their habitat
• MORPHOLOGICAL CONVERGENCE
organisms may have similar features but are
unrelated. This results from being exposed to
similar environmental conditions
• (ex. wombat vs. ground hog )
The Rate of Evolution
• Gradualism-(Darwin) small changes
accumulate over a long period of time.
(Transitional fossils would be expected)
• Punctuated Equilibrium- (Stephen J.
Gould) long periods of uneventful time
passes until a catastrophe creates
opportunities for new species to flourish.
Little change is punctuated by rapid
evolution of new species.
Evidence of relatedness
• Example: Transitional forms in the fossil
record
Hypothesis: If terrestrial vertebrates (tetrapods)
evolved from lobe-finned fish (sarcopterygians), then
there should be transitional forms that possess traits
that are intermediate.
Previously identified
transitional forms
From Ahlberg and Clack, Nature 2006
General Methods
• Scientists looked
specifically for the
transitional form of
interest by sampling…
From
Daeschler
et al., 2006
– Appropriate habitats
(stream system)
– Appropriate geologic time
(early Late Devonian =
385-376mya)
http://tiktaalik.uchicago.edu/photos.html
They found
Tiktaalik roseae!
http://tiktaalik.uchicago.edu/photos.html
From Ahlberg and Clack, Nature 2006
From Daeschler et al., Nature 2006
http://tiktaalik.uchicago.edu/photos.html
From Shubin et al.,
Nature 2006
Summary
• The study of and the evidence for
evolution clearly fits within the scientific
framework.
• We use current evolutionary theory to
make and test hypotheses
• There are many thousands of examples of
evidence for evolution
What about man?
• Where is the evidence of human ancestry?
What data from whole
genome sequencing can tell
us about evolution of humans
Example: the
Evolutionary Hypothesis
of Common Ancestry
Chromosome Numbers in
the great apes:
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
46
48
48
48
Testable prediction:
If these organisms share a common
ancestor, that ancestor had either
48 chromosomes (24 pairs) or
46 (23 pairs).
Ancestral
Chromosomes
Chromosome Numbers in
the great apes
(Hominidae):
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
Fusion
Homo sapiens
Inactivated
centromere
46
48
48
48
Telomere
sequences
Centromere
Telomere
Testable prediction:
Common ancestor had 48 chromosomes (24 pairs) and
humans carry a fused chromosome; or ancestor had 23
pairs, and apes carry a split chromosome.
Human Chromosome #2 shows the exact
point at which this fusion took place
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-tohead fusion of two acrocentric chromosomes that
remained separate in other primates. The precise
fusion site has been located in 2q13–2q14.1 (ref.
2; hg 16:114455823 – 114455838), where our
analysis confirmed the presence of multiple
subtelomeric duplications to chromosomes 1, 5, 8,
9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary
Fig. 3a, region A). During the formation of human
chromosome 2, one of the two centromeres
became inactivated (2q21, which corresponds to
the centromere from chimp chromosome 13) and
the centromeric structure quickly deterioriated
(42).”
Hillier et al (2005) “Generation and Annotation of the DNA
sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.
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Test topics evidence of evolution
EVOLUTION TEST #2
Notes over
Geological evidence of evolution
Biological Evidence of Evolution
Amino Acid Lab
Radiometric Dating
Text (282-292, 740, 327)
Vocabulary (105-113)
Worksheets x2 (History of Life and Evolution)
Plate tectonics Map Know the continents
Homologous vs. analogous
Gradualism vs. Punctuated Equilibrium
Comparative Anatomy Buffon (1-2-5)