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EVOLUTION
1.Early History of Earth
Early earth was inhospitable
• hot, with many volcanoes
• little free oxygen and lots of carbon dioxide
• other gases present: nitrogen, methane, ammonia,
hydrogen and water vapor
• Estimated age of earth: 4.6 billion years old
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2. How Did Life Originate on
Earth?
Miller & Urey (1953)
 Experimental set up:
1. Hydrogen, methane, ammonia, water sealed in a
sterile beaker
2. Water evaporated, condensed to simulate rain
3. Electrical sparks introduced to simulate
lightning
4. Result: organic compounds began to form,
including amino acids (building blocks of
protein)
2.
3.
1.
4.
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Once amino acids had formed, primitive life
developed. The process of evolution then allowed
more complex organisms to develop over millions of
years.
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3. Bacteria were the earliest life
Formed colonies called stromatolites
(age 3.5 billion years old)
Best colonies in Australia
Evolution of Cells (based on fossil record)
• First true cells—were probably prokaryotic,
heterotrophic and anaerobic
• single celled—no nucleus
• consumed food for energy
• did not need oxygen to survive
• Next came photosynthetic prokaryotes—releases
oxygen into atmosphere
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How did we get Eukaryotic Organisms?
Remember Eukaryotic organisms:
Have a nucleus
Have many organelles including Mitchondria,
Chlorplasts (in plants) ER, etc.
Are multicellular
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4. Endosymbiotic Theory
ENDO = Into
Symbiosis = relationship of two organisms living close
together
• Proposed by —Lynn Margulis of Boston University
According to the theory of endosymbiosis
• eukaryotic cells evolved when bacteria either
infected or were engulfed by a larger bacteria
cell
• later they established a symbiotic relationship
• eventually this evolved to one cell a Eukaryotic
cell.
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Endosymbiotic Theory Evidence:
• Mitochondria and chloroplasts contain DNA
similar to bacterial DNA.
• Mitochondria and chloroplasts have ribosomes
whose size and structure resemble those of
bacteria
• Like bacteria, mitochondria and chloroplasts
reproduce through binary fission(mitosis)
• Eukaryotic cells evolved from prokaryotic cells
Endosymbiosis Animation:
http://highered.mcgrawhill.com/sites/9834092339/student_view0/cha
pter4/animation_-_endosymbiosis.html
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What is Evolution?
Evolution is a theory that says that a species
undergoes gradual changes to survive and reproduce
in a competitive and often changing environment. A
new species is the result of development and change
from ancestral (older) forms.
Evolution is a change in living organisms over time.
http://www.youtube.com/watch?v=GhHOjC4oxh8
The History of Evolutionary Theory
Charles Lamarck (1809) described evolution as the
result of the "use and disuse" of organs and
"acquired traits.” Lamarck thought that if evolution
occurred it was through acquiring traits within an
organism's lifetime; these acquired traits were then
passed on to offspring. Lamarck was wrong!
Charles Darwin explained how
evolution occurred through
natural selection. He revealed
this theory in his 1859 book
On the Origin of Species, by Means of Natural
Selection.
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Darwin arrived at this
theory from his
experiences while
traveling on the HMS
Beagle as a naturalist, and
through the writings of
others :
Charles Lyell: Father of geology who said that the
earth has changed over time (based on his studies of
rocks and geology).
Thomas Malthus: British economist who said that
populations increase faster than the food supply.
Because of this, there is a struggle among living
things for food and shelter.
On his journey on the Beagle, Darwin
noticed that finches on the Galapagos Island
looked similar except for the shape of their
beak.
He concluded that the finches were all
descendents of the same original population. The
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shape of the beaks were adaptations for eating a
specific type of food (Ex: long beaks were used
for eating insects, short for seeds)
** Alfred Wallace came to the same conclusion as
Charles Darwin at the same time - both scientists
are credited with developing the theory of natural
selection.
THE THEORY OF NATURAL SELECTION SAYS:
1. In nature there is overproduction.
2. Not all offspring survive.
3. Variations exist in populations.
4. Variations are inherited.
5. Individuals with variations that are suitable to
their environment will live longer and leave more
offspring than individuals without the variations.
This is called ‘survival of the fittest.’
6. The resulting population will change as it becomes
better adapted to its environment.
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**In short, this theory
states: nature or the
environment selects which
organisms will survive and
reproduce.
Consider the evolution of
giraffes from the natural
selection view of evolution and
the Lamarckian view.
We know that Lamark was wrong!!
Evolution is the change in species over time.
Darwin made two main points in The Origin of
Species:
1. Today’s organisms descended from ancestral
species.
2. Natural selection is the cause of evolutionary
change in populations.
http://www.youtube.com/watch?v=0SCjhI86grU
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Types of Natural Selection
Three Types of Natural Selection
Directional Selection
Stabilizing Selection
Disruptive Selection
Direction Selection
Prefers individuals that have extreme values
of a trait
This causes the population to move in a
particular direction
Example -If a climate becomes colder, a
population may evolve in a consistent direction
from thinner fur to thicker fur.
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Stabilizing Selection
Acts against individuals who move too far
away from the average,
Prefers the average (color, size etc.)
Example -Sizes in lizards: large lizards may be
subject to predation; small lizards may have a
hard time defending territories, natural
selection favors the average
Disruptive Selection
Adapts individuals in a population to different
habitats.
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Similar to directional selection—but it
prefers either extreme (small and large
lizards) (big beaks and small beaks)
Acts against the average (medium lizard or
medium beak)
May occur in an area that provides very
different resources
Example- Galapagos finches had a variety of
food choices: smaller birds fed on small seeds,
larger birds feed on large seeds. Natural
selection favors both small and large see birds
but not the average who would compete for
both resources.
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What is the Scientific Evidence for
Evolution?
1. Fossil Record: Bones and other traces of
organisms that lived long ago show that organisms
have changed over time.
2 ways of dating fossils
oRelative dating
oRadioactive dating
o
Rocks of
different ages
show that
different
species lived at
different times.
This is called Relative Dating.
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Radiometric dating (radioactive dating)
This is called Radiometric dating.
exact age of the fossil.
It gives an
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Evidence for Evolution continued
2. Comparative Anatomy: The study of structures
of different organisms show that they share
similar structures.
These are called homologous structures. They are
similar because of shared ancestry
3.Comparative Embryology: The study of different
kinds of developing organisms (embryos) show many
similarities not seen in the same full grown
organisms.
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4.Artificial Selection: Evolution can be
observed today! Artificial selection is the
process of breeding domestic plants and
animals to produce specific desirable features
in a population.
http://www.youtube.com/watch?v=tukxnJ8Gnbg
dog breeding
5.Genetic Evidence: An examination of the base
sequences of DNA from different organisms
indicates common ancestors.
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6. Direct Observation:
Antibiotic Resistance - This is observed whenever
bacteria develop resistance to an antibiotic (Ex:
penicillin) or insects develop resistance to
pesticides.
http://www.youtube.com/watch?v=tQZnhjJnD5E
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Peppered Moths
Originally, the majority of peppered moths had light coloration which
camouflaged them against the light-colored trees and lichens which they
rested on. Because of pollution during the Industrial Revolution in England
many of the lichens died, and the trees became blackened by soot. This
caused most of the light-colored moths to die off from predation. The
dark-colored moths did well because they could hide on the dark trees.
This is called Industrial Melanism.
http://www.youtube.com/watch?v=LyRA807djLc
Pesticide/Insecticide Resistance
Insecticides are poisons that kill insects. An application of a new
insecticide typically kills 99% of the insects. The effectiveness of
insecticides becomes less over time.
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7. Vestigial Structures: These are anatomical
structures (organs) in a species that have lost
much (or all) of their original function through
evolution. Examples in humans are the tailbone
and the appendix.
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This mole has tiny eyes but
cannot see. He lives underground.
Whales have hind limb bones.
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Add: 8. Analogous structures
• Outwardly similar structures
• The same function, but not the
same bone structure
• Are not closely related
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Evolution Key Terms You Need to Remember:
Species - Like organisms that are capable of
interbreeding under natural circumstances
Gene Pool – Collection of all the genes for
all of the traits in a population.
Variation- Differences among a population;
variations are necessary for natural
selection.
• Genetic variation refers to the variety of
alleles in a population.
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Adaptation- traits that help an organism survive and
reproduce over many generations; many small
modifications together produce important
adaptations.
Types of Adaptations:
 Structural- Structural or anatomical
o
Example: beak shape, tooth shape, anglerfish’s
lure, elephant’s trunk
 Physiological- Biochemical
o Example: poisons, octopus ink
 Behavioral- Actions to respond to the
environment.
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o Example: migration, group hunting,
plants leaning toward light, a bear
hibernating
How and When does Evolution Occur?
• Natural selection causes changes in a population.
If a population changes so much that it becomes a
new species, it is called speciation.
• Speciation- Evolution into separate
species is caused by:
1. Geographic isolation: A population
of organisms is separated by a barrier like a
river, canyon or mountains
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2. Reproductive isolation: Interbreeding or
fertilization is blocked because of
different mating habits, chromosome #’s
3. Genetic drift: Rapid changes in the # and
types of genes in a small isolated
population.
Genetic drift may occur when a small group
of individuals colonizes a new habitat.
4. Adaptive radiation: Variation within a
population allows small
groups to move into new
habitats & be successful
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• Evolution occurs in populations, not individuals.
Individuals do not evolve, but are part of
populations which do.
• Evolutionary changes are not necessarily always
"good"! Natural selection selects for the
organism best adapted to the environment.
Example: Sickle cell anemia Ss survive malaria.
Evolution is a genetic change occurring in a
population of organisms over many generations. It is
a change in allele frequency (the gene pool changes).
What are Types of Evolution?
• Divergent evolution: One species evolves into 2 or
more with different characteristics
Divergent Evolution
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• Convergent evolution: Species that are
not closely related evolve similar traits,
behaviors, or characteristics
Example: fish & dolphins
Example: Marsupials (pouched animals) of
Australia (Kangaroo) and North America (Opossum)
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These organisms have analogous structures.
• Coevolution: Interactions of different species
lead to mutual adaptations
Example: plants and pollinators, lichen
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• Microevolution- Evolution that results from small
specific genetic changes that can lead to a new
subspecies Ex: Peppered Moths
• Macroevolution- evolution on a large scale;
extending over large areas and long time periods.
The Ice Age
Evolution can be Fast or Slow:
 Gradualism- Slow & steady change over great
lengths of time
Slow
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 Punctuated equilibrium- Sudden changes in the
environment cause rapid evolution, followed by long
periods without change
Fast
ENDOSYMBIOTIC THEORY
• In 1970, American
biologist, Lynn Margulis,
provided evidence that some
organelles within cells were
at one time free living cells
themselves
• Supporting evidence included
organelles with their own
DNA
• Chloroplast and
Mitochondria
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Where do Humans Fit?
Humans are animals…mammals… primates
Common characteristics
Problem solving, large brain, flexible hands
rotating shoulders, 5 digits, and opposable
thumb
There are three types of natural selection: stabilizing, disruptive
and directional.
Stabilizing: Birth Weight of Babies
Stabilizing selection takes place
when individuals near the
center of a curve have higher
fitness than individuals at
either end.
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Disruptive: Beak Size in Birds
A population of birds
lives in an area where
medium-sized seeds
become less common
and large and small
seeds become more
common.
A population of birds lives in an area where medium-sized
seeds become less common and large and small seeds
become more common.
Directional: Thick beaks in
seed-eating birds.
When individuals at one
end of the curve have
higher fitness than
individuals in the middle
or at the other end,
directional selection
takes place
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