Evolution
15.1 Evidence of Evolution
15.6 Domains & Kingdoms
15.8 Origin of Life
15.13 Natural Selection
Origins of
Life on
Earth
Earth History

Evolution is studied using concepts about earth history. The earth is
between 4.3 and 4.5 billion years old.

Approximately 3.9 billion years ago, the surface was likely cool
enough for water vapor to condense and form oceans

Geological evidence suggests that cells similar to modern bacteria
were common 3.8 billion years ago.
How did life on Earth begin?
Until the 1700’s people believed that living
things could come from nonliving substances,
spontaneous generation.
Spontaneous generation: Pasteur’s experiment
• Experiment: Pasteur filled a flask with broth with a long S shaped neck.
He boiled it to kill all life. It was open and exposed to air, but anything in the
air got stuck on the curves of the neck.
• Conclusion: Spontaneous generation was disproved and biogenesis
theory was substantiated. Contamination came from other
microorganisms, not “air”.
Original Conditions on Primitive Earth to
make life….
 Presence
of liquid water
 Moderate temperature range
 Free oxygen in the atmosphere
(contributed by cyanobacteria)
 Adequate sunlight
 Absence of toxic substances in
atmosphere
 Absence of lethal radiation
Volcanoes Play a BIG Role
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Water vapor (eventually condensed and fell as RAIN)
Methane
Hydrogen
Nitrogen
Ammonia
Carbon Dioxide (we now have oxygen b/c of photosynthetic
bacteria)
Carbon Monoxide
OXYGEN ATMOSPHERE

Remember the atmosphere of early
Earth was made up of nitrogen, carbon
dioxide, water vapor, but no free oxygen

Oxygen comes from photosynthesis
when leaving oxygen gas.

About 2 billion years ago, the oxygen
level in the atmosphere started to rise.
Aerobic metabolism, much more
efficient than anaerobic, became
possible.
Question
What are the reactants in photosynthesis?
The products?

The evidence of oxygen gas
formation can be seen in
rocks when layers of iron
oxide on the bottoms of
oceans stopped forming
when oxygen appeared.
Cyanobacteria created
the oxygen in the
atmosphere.
Theory of Chemical Evolution
“Primordial Soup Theory”

Conditions on the early Earth were
very different.
The atmosphere had no oxygen
 Energy sources, such as lightning, volcanic activity, and ultraviolet
sunlight (no ozone layer)

Chemical Evolution
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Earth’s early atmosphere: HCN, CO2, CO, N, H, S, H2O
“Life arose from the oceans”
He believed that energy from lightning and the sun can
spark chemical reactions to create AMINO ACIDS that
made proteins.
Chemical Evolution
Urey and Miller
Created in the laboratory,
the conditions of early
Earth.
 They discharged sparks in
an “atmosphere” of the
Miller-Urey model consisted
of H2O, H2, CH4, and NH3
gases.
 produced a variety of
amino acids and other
organic molecules.

Chemical Evolution
• Alternate sites proposed for the synthesis of organic
molecules include
• submerged volcanoes and deep-sea vents where hot
water and minerals gush into the deep ocean.
Prokaryotes
Prokaryotes were the earliest organisms on
Earth and evolved alone for 1.5 billion years.
• two prokaryotic domains:
Bacteria
and
Archaea
•
Prokaryotes
• have
a cell wall external
to the cell membrane
• Lack membrane bound
nuclues and organelles
• Double-stranded DNA
molecule is in a single ring
shaped
Evolution
Process by which species of organisms change over
time
 Thing evolve around us all the time
 Based on scientific evidence such as…
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Fossils
Comparative morphology/anatomy of organisms
Embryology
Analysis of genetic material (DNA analysis…DNA
fingerprinting!)
Terms to Know
Species
◦ a group of organisms that share similar
characteristics and can interbreed to
produce fertile offspring
◦ As species EVOLVE, they produce new
traits and lose other traits….
 Adaptation
◦ Any physical or behavioral trait that
improves an organisms chance for
survival and reproduction

Fossil Evidence for Evolution

Fossils:
◦ Remains or evidence of organisms that have lived in the past
◦ Provided clues of when different species lived

Law of Superposition
◦ States that in undisturbed sedimentary rock, older rock layers
lie beneath younger rock layers
◦ By Identifying the fossils indifferent layers of rock and
applying the law of superposition, scientists can determine:
 when the certain organisms lived
 The order in which things evolved
Law of Superposition
Biogeography

Study of the distribution of Earth’s organisms
 Continental Drift Hypothesis
◦ States that the continents were once joined in a single,
large landmass called PANGAEA
◦ Pangaea broke up over millions of years and continents
ended up where they are today
◦ Fossil evidence shows that in addition to changing
Earth’s surface, continental drift also changed the
distribution of organisms on Earth
Comparative
Anatomy/Morphology
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Do other organisms have arms like us?
Many species share similar structures..
Do flamingos and blue jays have
feathers?
◦ Yes…the presence of feathers
suggest that both groups of birds
descended from an animal with
feathers
◦ Flamingos and blue jays are more
closely related than either one is to
an animal without feathers (like us)
Homologous Structures
Body parts of different
organisms that have similar
structure but NOT similar
FUNCTION
 Homologous structures DO
indicate shared ancestor
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Analogous Structures
Body parts that have a SIMIALR FUNCTION but NOT
similar structure
 Body parts with Different structure, same function
 Do NOT indicate shared ancestry
 An analogous structure found in two different species

Homologous vs. Analogous Structures
 Homologous= Same structure, DIFFERENT
Function
 Analogous= Different Structure, SAME
Function
Comparative Anatomy
Anatomical features that are similar in structure are called
homologous structures, and they indicate common
ancestry.
Vestigial Structures

Structures that do not seem to play a role in the
body functions of the organism
◦ Appendix
 Rats digestion
 Humans no use…appendix is a vestigial structure
 It can be concluded that the common ancestor of the human
and rat had an appendix
Embryology
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Study of embryos
Embryo early stage in the development of
an organism
Scientists compare the development of the
embryos of different species
Similarities in development =shared
ancestor
More traits in common=more closely related
Modern Organisms
EVOLVED from COMMON
Ancestors in an
Evolutionary Chain
Chemical Evidence of Evolution

Chemicals found in living things also
provide clues to ancestry..what chemical?
◦ DNA!!!
Comparisons of the sequences of the
nucleotides in DNA and the amino acids in
certain proteins can also be used to show
more common ancestry
 More similarities in two DNA sequences or
amino acid sequences = the more closely
related the organisms are
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◦ DNA fingerprinting
ALL organisms have DNA made up of the same
Amino Acids…
The only thing that’s different is the
ARRANGEMENT/sequence of amino acids…
The More similar AA sequences= the
more closely related the organisms
are!
Similarities in Molecular Biology
Common amino acid sequences suggest an
evolutionary relationships between various species
of organisms.
Darwin’s Theory of Evolution
by Natural Selection
Ideas that shaped
Darwin
◦ Before Darwin people believed Earth was less than 10,000
years old and also relatively unchanged
 Buffon- Studied the fossil record which showed that the Earth might be much
older.(4.3 and 4.5 billion years old)
 Hutton - Layers of rock are moved by forces beneath Earth’s
surface. Most geological processes operate extremely slowly.
 Lyell - geologic process that shaped the Earth in the past still continue today.
Ideas that shaped Darwin
Before Darwin people believed that species were fixed,
plants and animals had always been the way they are
today
Cuvier – based fossils from different rock layers gave evidence that
organisms from the past differed greatly from living species
Ideas that shaped Darwin
Lamark’s
Use or disuse
1st to suggest that species change or evolve
over time.
But his explanation was flawed.
He thought characteristics acquired
through your life could be passed
down from parent to offspring.
Voyage of the Beagle
Darwin made a voyage around the word collecting thousands of plant and animal
specimens.
 His observations and collected evidence led him to propose hypothesis that living
things change over time
 Theory of Evolution through Natural Selection.
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Voyage of the
Beagle
 Darwin
noticed that plants
and animals on the
Galapagos islands of the
coast of Ecuador were
different from those on the
mainland and also from
island to island.
Neck-size vs. Vegetation height
Galapagos’ Finches
Galapagos’ Finches
Darwin’s Theory
In 1859, Darwin published a book titled,
 “On the Origin of Species”
 In this book he presented all the evidence he had gathered
over the past several years supporting his theory that evolution
has been taking place for millions of years—and continues in
all living things.
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•
•
In his book he also proposed a mechanism for
evolution called
Natural Selection
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Speciation
◦ Evolution of a new species from an existing
species
◦ Due to Types of isolation…more on next slide
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Occurs when a population is separated into
groups that cannot reach each other to
interbreed
◦ Due to :
 Behavioral barriers
 Anatomical barriers
 Genetic barriers
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Once groups are separated, environmental
conditions in each area influence which traits are
helpful or harmful to members of each population
◦ Less helpful traits disappear
◦ Helpful traits become more popular
Overtime, these changes can produce 2 distinct
species that can no longer interbreed
Observed Evolutionary
Change
How We Get New Species
Reproductive isolation
◦ When organisms of the same species become genetically split
and STOP breeding with each other
◦ Gene pool split, two different groups can no longer interbreed
 Behavioral isolation
◦ Groups of organisms of the same species develop different
courtship rituals (or behaviors) over time and will not be attracted
to others
 Geographic isolation
◦ When two populations are separated by geographic barriers
◦ Mountains, rivers, etc.
◦ Doesn't always separate all species…river and birds vs. squirrels
 Temporal isolation
◦ When two or more species reproduce at different times
◦ Specific day/season when that species is able reproduce
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Allopatric speciation means that speciation
occurred in different regions. The key with
allopatric speciation is geographical
separation.
Sympatric speciation means that one
population of one species became two
species while in the same geographic region
with no physical separation.
Adaptive Radiation
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Where species all deriving
from a common ancestor
have over time successfully
adapted to their
environment via natural
selection
Niche
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Derived from Latin word
meaning “nest”
The role an organism plays in its
community or ecosystem
No two species can occupy the
same niche in the same area at
the same time
Think of a sports
team…everyone has a specific
role on the field
◦ You can’t have two people playing
short stop at the same time
Terms to Know
Two Ways Evolution is believed to have Occurred
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Gradualism
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Evolution occurring over a long period of time
Slow and constant change
Small difference between generations
This is how Darwin believed NATURAL
SELECTION worked
Punctuated Equilibrium
◦ Evolution occurs in spurts
◦ Changes occur rapidly followed by long
period without change
◦ Causes:
 random mutations in DNA
 Sudden Major changes in environment
Convergent Evolution
 organisms that descended from different
ancestors
 Evolve similar anatomies and/ or behaviors
if they live in similar environments
 Organisms
from the
same ancestor have
developed different
anatomies/behaviors
(and eventually form
new species)
 Environment
influences their new
anatomy/behaviors
Divergent Evolution
Microevolution
When evolution occurs quickly enough for
scientists to observe
 Bacteria

◦ Reproduce rapidly
◦ Trait for Resistance to antibiotics is passed down to
offspring
◦ This is how bacteria become resistant to certain
medicines…NOT GOOD
NATURAL SELECTION
The ability of an organism to survive and
reproduce in its specific environment is
called fitness.
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•
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Individuals with characteristics that are
not well suited to their environment either
die or leave few offspring
Individuals that are better suited to their
environment survive and reproduce most
successfully.
Darwin called this process Survival of
the Fittest, or Natural Selection.
4 Principles of Natural Selection
Variation
Competition
Excess
offspring
Survival of the Fittest
4 Main Principles of Natural
Selection
1.
2.
3.
4.
Variation exists within a
population
Organisms compete for
limited resources
Organisms produce more
offspring than can
actually survive
Individuals with variations
suitable for their habitat
are the ones that SURVIVE
and REPRODUCE
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Three species of lizard.
B- The ones at the bottom live in the shrubland, and are colored to blend in.
•The top pictures show the same species
of lizard, but the variety that lives in the
White Sands
•They all evolved to become white
(camouflage)
•The DNA on the bottom shows the
location of the mutation that gives the
white color
1. Inherited Variation
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Individual organisms within the population differ.
Most of this variation is determined by genetic
inheritance (recombination), but sometimes it is the
result of genetic mutations.
More on Variation
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What is a gene?
◦ Section of DNA on your chromosome that codes for a particular
protein=trait
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Genes determine a particular trait an organism expresses
Many times organisms can have duplicate copies of a gene
◦ think of these copies as back up files
◦ Sometimes the back up files get mutated by they are not expressed
◦ If an environment changes, that mutated copy of the original gene
MAY be useful if it helps the organisms survive
◦ The mutated copy may then be passed onto offspring
2. Struggle for Existence
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Because so many offspring are produced, many
will die due to a lack of resources, predation,
disease, or other unfavorable conditions.
3. Overproduction of Offspring
Organisms produce more offspring than can survive.
Many of the offspring do not survive to reproductive age.
4. Differential Reproduction
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Individuals best suited to their environment survive and reproduce
most successfully.
Therefore these organisms pass their advantageous traits to their
offspring while offspring with disadvantageous traits die or produce
fewer offspring.
Descent with Modification
 Natural selection
causes species to
change over time.
 Species
alive
today descended
with modification
from ancestral
species.
Diving Into The Gene Pool!
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Different forms of genes
Genes
◦ Sections of DNA that code for a specific
protein that give you a specific trait
◦ “factors” that determine an individuals
characteristics; passed down from
parents to offspring
Gene Pool
◦ All the genes (including different alleles)
in a population
◦ Gene Pool: the combined genetic
information of ALL members of a
population
Allele frequency is the # of times a specific
allele occurs in a gene pool
Evolution involves changes in ALLELE
FREQUENCY in a population over time
• Allele: One gene of a gene pair for a trait.
• In the gene pair Bb for hair color, both
B & b are alleles
• Genotype: The 2 alleles an organism
possesses for a trait. (Its genetic makeup.)
• Phenotype: The external appearance of the
organism for a trait. (blue eyes, black hair,
hitchhiker's thumb, etc...)
• Dominant Allele: An allele that masks the
presence of another allele for the same
characteristic. Usually shown as a capital
letter (Ex......A, B, G, T, etc....)
• Recessive Allele: An allele that is hidden by
the presence of a dominant allele for the
same characteristic. Usually shown as a
lower case letter (Ex......a, b, c, t, etc....)
How to calculate the ALLELE Frequency in
a Gene Pool
Allele X or Allele x for certain TRAIT
Allele frequency X = # of allele X in population (gene pool)
total # of alleles (X + x) in population (gene pool)
Allele frequencies measure genetic variation.
– how common allele is in population
– can be calculated for each allele in gene pool
1. Calculate the allele frequency for G(Green frogs) in the population
2. Calculate the allele frequency for g (brown frogs) in the population
Genetic Diversity Is Important in
Evolution
 Within
a population there MUST be
genetic diversity to INCREASE
chances of surviving and
reproducing
 Genetic variation is caused by:
◦ Gene flow
◦ Genetic drift
◦ Non-random mating
Genetic Drift

changes in the allele frequency within a population that occur by chance
Before
After
genes of the next generation will be the genes of the “lucky” individuals,
not necessarily the healthier or “better adapted” individuals
 Some individual may have more offspring than others, although both
groups are equally fit

◦ Bird A and Bird B lay eggs
◦ Predator steals Bird A’s eggs
◦ Who’s gene will be passed on?
No guarantee that the new population will be better suited to its
environment than the original population
 Genetic drift is more likely to effect small populations

Gene Flow
 genes from one population are
introduced into the gene pool of
another population
◦ Biggest Factor that Effects Gene Flow: MOBILITY
 For
example:
 The immigration and emigration of organisms.
 The dispersal of seeds or spores.
Hardy-Weinberg Equilibrium
 principle stating that the genetic
variation in a population will remain
constant from one generation to the
next in the absence of disturbing factors
 Cannot exist in real life; a way to see
how alleles change in a population
 NO EVOLUTION WILL OCCUR WHEN
THESE 5 CONDITIONS ARE MET—GENETIC
EQUILIBRIUM
5 CONDITIONS:
1. No mutations must occur so that new alleles do
not enter the population.
2. No gene flow can occur (i.e. no migration of
individuals into, or out of, the population).
3. Random mating must occur (i.e. individuals must
pair by chance)
4. The population must be large so that no genetic
drift (random chance) can cause the allele
frequencies to change.
5. No selection can occur so that certain alleles are
Weinberg Equation
not selected for, or against. Hardy
2
2
p + 2pq + q = 1 and p + q = 1
Non-Random Mating
 Some individuals in a population
have more opportunity to mate and
produce offspring than others
 Genes of individuals with less
chances to mate are eliminated from
population
 Common in animals b/c animals
choose their mates
Another source of genetic variation…
Genetic variation comes from several sources.
Can you think of some?

Mutation is a random change in the DNA of a gene.
– can form new allele
– How can mutations be
passed on to offspring?
• Recombination forms new combinations of alleles.
– usually occurs during meiosis,
What is the process called?
–CROSSING OVER
–parents’ alleles
arranged in new
ways in gametes
Sources of Genetic Variation

Mutation
◦ Somatic mutations (to your regular cells with 46
chromosomes)
◦ Germ mutations (to your gamete cells with 23
chromosomes)

Recombination
◦ Rearrangement of genes
◦ Gives offspring combinations of genes different from
those combinations in parents
◦ Sources of recombination:
 Sexual reproduction
 Chromosomal changes during gamete formation
Mutations
 Change
to an organisms genetic material
(DNA)
 Change the NUCLEIC ACIDS that make up
one or more genes
 Changes can produce new traits that can
either HELP or HURT the survival of an
organism
◦ BENEFICIAL Mutations help organism
◦ NEUTRAL Mutations have no effect on organism
◦ NEGATIVE Mutations hurt organisms chances for
survival
Germ Mutation
Mutation in a gamete
 CAN BE passed off to offspring and AFFECT survival
of those offspring and their descendants
 Helpful mutations persist (stay around) in
population
 Helpful mutations contribute to evolution and
speciation

Reasons for Mutations
Spontaneous
Natural
factors
◦Ultraviolet radiation from the
sun
Exposure
to chemicals
Exposure to radiation
Summary of Evolution
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DNA is the blue-print for building ALL living things on planet Earth.
DNA sequences are changed by:
 random mutations
 Radiation
 Viruses
 Chemicals
 sexual reproduction
 Migration
 geological events
As a result there is variation within populations of a species.
Those individuals of a particular species with a phenotype (as a result of
their genotype) that is more fit to survive in a given environment has a
better chance to reproduce.
Those individuals who reproduce more pass-on their genes at a higher
frequency than those who do not.
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EVERYTHING is trying to SURVIVE and REPRODUCE