Evolution
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Quick Review of Microevolution
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• Punctuated Equilibrium
– Quick & noticeable changes
• Gradualism
– Slow evolution over a long period of time
• Convergent Evolution
– Two different species becoming more alike
• Divergent Evolution
– One species splits into two and becomes less alike
• Coevolution
– Two different species living in close association evolve together
• Natural Selection
– Unfit traits die out
Microevolution Review
• Label the pictures in the next section
– Your options are underlined in the section above
A=Gradualism ;
A
B
B= PE
Divergent Evolution
Coevolution
Convergent Evolution
II. Macroevolution
- The evolution of all organisms on a grand
scale, larger than the changes at the species
level.
- The same mechanisms that affect
microevolution can be used to explain
macroevolution. (such as migration, genetic
drift, and natural selection)
- All organisms have evolved from one or a few
common ancestors.
A. Evidence for Evolutionary Theory
1. Geology
– Indicates a gradual change of the
earth and its environments over
time.
• Plate Tectonics & continental drift
• radioactive dating (determining age of
radioactive isotopes using half-life)
• weathering
• volcanic activity
2. Fossil Record
a. Dead organisms form a mold (imprint) or cast
(mineral filled mold) in sedimentary rock.
b. Usually only shows hard body parts although
sometimes under the right conditions other parts
can be petrified (preserved).
c. Law of Superposition- older rock layers are
deeper; younger rock layers are closer to surface
- The layers, or strata, show the relative age
of fossilized organisms.
2. Fossil Record (cont. )
d. The fossil’s absolute age (age in years) can be
determined by radioactive dating of the rock the fossil is
found in.
-Radioactive Dating: Process by which traces of
radioactive elements are analyzed to calculate the
actual age of a fossil (see below)
e. The fossil record indicates that organisms species arose,
became extinct and gave rise to new species throughout
Earths history ( about 4.5 billion years)
f. The oldest prokaryotic fossils are about 3.8 billion yrs old.
Modern humans have been here for about 100,000 yrs
g. Transitional fossils have been found that link present
species to the past
Carl Sagan- Cosmos (edited for rednecks)
a
b
x
o
December 31- 11:48 PM
Modern humans
Radioactive/Radiometric Dating
• How it Works:
– Radioactive elements decay (break down into different
elements) at specific rates
• Decay rate is called a half life
– Ex: Carbon-14’s half life is 5730 years
» So it takes 5730 years for half of C-14 to decay
– These rates are nearly constant
• Once this rate is known, geologists can estimate
age by measuring the amount of radioactive parent
element vs. the amount of stable daughter
elements
– The amount of parent that has decayed determines
the fossil’s age
Scientist Measure the Age of the Earth
Radiometric Dating: way of estimating the age of the
Earth!
http://www.pbs.org/wgbh/evolution/library/03/3/quicktime/l_033_01.html
Radiometric Dating
Radioactive
Parent
Stable
Daughter
Half life
Potassium 40
Argon 40
1.25 billion
yrs
Rubidium 87
Strontium
87
48.8 billion
yrs
Thorium 232
Lead 208
14 billion
years
Uranium 235
Lead 207
704 million
years
Uranium 238
Lead 206
4.47 billion
years
Carbon 14
Nitrogen 14
5730 years
How to do radiometric dating
1. Write the amount of parent material left as a
fraction (This will be given to you in a problem)
2. Determine the # of halves that go into the
fraction
– # of halves= # of half-lives
3. Multiply this number by the half-life decay rate
(years)
Practice Problems
Ringholz-19 ’s half life= 10 years
(So it takes 10 years for half of R-19 to decay)
1. There is 1/4 of R-19 remaining in a sample
1. There is 1/16 of R-19 remaining in a sample
Carbon-14 Dating
• Determines the age
of fossils of a
biological origin up to
approx. 50,000 years
old.
– Used in dating things
such as bone, cloth,
wood, plant fibers,
etc.
5,700 year is
C14 half-life
Radioactive Dating Practice
Carbon-14 half-life= 5730 years
• There is 1/32 remaining of C-14 in a sample
• There is 1/8 remaining of C-14 in a sample
Half-life of carbon-14 is 5730 years
Half-life of carbon-14 is 5730 years
22,920
11,460
28,650
17,190
• Fossil record activity
Parent
Daughter
Half-life (yrs)
Potassium 40
Argon 40
1.25 billion
Rubidium 87
Strontium 87
48.8 billion
Thorium 232
Lead 208
14 billion
Uranium 235
Lead 207
704 million
Uranium 238
Lead 206
4.47 billion
Carbon 14
Nitrogen 14
5730
Pop QuizDating
Parent
Daughter
Half-life (yrs)
Rubidium 87 Strontium 87 48.8 billion
Thorium 232 Lead 208
14 billion
Uranium 238 Lead 206
4.47 billion
Carbon 14 Nitrogen 14 5730
1. How old is a sample if 1/4 of it is Rubidium 87?
2. You find a sample and most of it is Lead 208. What is
the rest of the sample made of? (no math on this
one)
3. You analyze a sample and find that it is 5 parts
Uranium 238 and 155 parts Lead 206. How old is it?
3. Homologous and Analogous Structures
a. Homologous structures- similar features that
develop from the same part of an embryo
– may have different functions now
– Examples:
• Hands and feet of humans and the paws of cats and dogs.
• Wings of birds and the arms of humans
• Bones that support the gill arches of fish, Bones in the back of the jaw in
reptiles, and the tiny bones in the middle ears of humans.
Homologous forelimbs
How this supports evolutionary
theory:
Homologous Structures:
• Provides evidence for divergent evolution and
common ancestry
– Structures show how they came from the same
ancestor, but have evolved into different things
over time.
– species that have homologous structures have a
fairly recent common ancestor
b. Analogous structures – structures of
similar function, but look different.
• structures have evolved independently and differently.
• Examples:
– Wings of birds, bats, and insects
– Fins/flippers on shark, penguin, and dolphin
Analogous wings
How this supports evolutionary
theory:
Analogous structures:
• Provides evidence for convergent evolution
– Two different parent species, but now look more
similar
4. Vestigial Structures- features that no longer
seem to serve a useful purpose in an organism.
Examples:
-Whales have a pelvic bone and some have
small hind-limb bones.
-Humans have ear muscles, tail bone,
appendix
Human vestigial structures
How this fits into evolutionary theory:
Vestigial structures:
• Provides evidence for common ancestry
– shows a relationship between organisms that still
have the vestigial feature and ones that have a
functional version of it.
5. Embryology – the study of embryos and
their development
How this supports evolutionary theory:
- similarities in the development of all
vertebrate embryos indicates that they share a
common ancestor.
- the closer the developmental stages the
closer the two organisms are related.
Embryo Development
Which is the
human embryo?
PIG FETUS
Answer: All of
them except the
one above,
which is a pig.
6. Similarities in Macromolecules
a. DNA, RNA, proteins, energy producing
organelles, chemical pathways all are the same or
similar in all living organisms.
b. Evidence shows that the evolutionary
relationship of organisms can be determined by
how close their genetic codes and proteins are.
c. Modern genetics has given us an explanation
as to how evolution of organisms has occurred
over time.
BIOCHEMICAL EVIDENCE
DNA, Amino Acids, Cytochrome C are similar in related organisms
How this supports modern evolutionary theory:
• Since all organisms use the same or very
similar macromolecules/cell structures, they
must have had a common ancestor
• Can determine how closely related two
species are by comparing genetic codes
Questions
Answer in complete sentences!
1. In your own words, explain how each of the
following provide evidence for modern
evolutionary theory:
a.
b.
c.
d.
e.
Homologous structures
Analogous structures
Vestigial structures
Embryology
Similarities in Macromolecules
2. According to Lamarck’s theory of evolution,
would vestigial structures still exist? Explain.
7. Population Genetics- the study of the frequency and
interaction of alleles and genes in populations.
a.a. Gene
poolcomplete
set
ofblue
allgenes
alleles for a gene in a
Gene Poola swimming
pool filled
with
single population.
b. Allele frequency- fraction of each allele in the gene
pool
c. Gene Flow- exchange of genes between populations
d. Genetic drift- change over time due to chance
Darwin Awards (darwinawards.com)
Named in honor of Charles
Darwin, the father of
evolution, the Darwin
Awards commemorate those
who improve our gene pool
by removing themselves
from it.
e. Hardy- Weinberg Equilibrium Model
- evolution will NOT occur if the following
conditions are met:
1. no mutation
2. no natural selection
3. the population is infinitely large
4. all members of the population breed
5. all mating is totally random
6. everyone produces the same number of offspring
7. there is no migration in or out of the population
8. No genetic drift (no random events)
* all of this is obviously not possible, which is why
we see evolutionary changes in species
How this model is used to provide
evidence for evolution:
• The H-W model can be used to identify if
evolution has occurred
1. Find the allele frequencies for the population
2. Compare those frequencies to the next
generation’s frequencies
• If frequencies are the same: no evolution
• If they are different: evolution has occurred!
f. Hardy-Weinberg equation- used to determine probable
genotype frequencies in a population and track the changes in
future generations.
p+q=1
p2 + 2pq + q2 = 1
p = frequency of the dominant allele in the population (A)
q = frequency of the recessive allele in the population (a)
p2 = frequency of homozygous dominant individuals (AA)
2pq = frequency of heterozygous individuals (Aa)
q2 = frequency of homozygous recessive individuals (aa)
Practice Problem 1
• If q= .35,
• First find p.
• Now that we know p and q, we can complete
the chart below!
H-W Practice Problems
• Do sections A and B
– Section A
• given p or q
• Find all the other frequencies
– Section B
• Follow the steps listed on the page!
• These examples are how you will be tested!!!
Practice Problem
• Cystic fibrosis is a recessive condition that
affects about 1 in 2,500 babies in the
Caucasian population of the United States.
• Fill out the chart and answer the questions if
there are 197 million Caucasian people in the
US .
Practice Problem
• Say in beetles, brown coloration is dominant
over green. You sampled an area and find 100
beetles, with 25 being green.
• Ten years later, you sample the area again and
find that there are now 500 beetles, with 175
being green. Has evolution occurred? Explain.
Practice Problem #4
For this problem you are making a prediction
about the next generation, assuming evolution
has not occurred.
– In a flock of 68 scarlet tanagers (type of bird), 14
have a white cap (a recessive mutation). They
breed and successfully raise 94 chicks. How many
of these chicks do you expect to have a white cap?
• Hint: Find the homozygous recessive frequency (q2)
– Then multiply that frequency by the new population size.