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What is Evolution?
Evolution- the genetic change of
populations over time
Population- group of organisms of the
SAME species that occupies certain area
Species- organisms that can interbreed
and produce FERTILE offspring
– Ex) populations in Sauerman Woods Crown
Point
-whitetail rabbits
-sparrows
-deer
-squirrels
Liger (lion and tiger)-infertile
Cama (camel and llama)-infertile
How Do We Know Populations
Evolve?
Population Sampling- technique uses part
of population to represent whole
population
Capture 100 random rabbits
– These rabbits are a representation of all the
rabbits in the area.
– We can study many things within this group…
Genetics of the Population…
Gene Pool- all of the
genes of every individual
in population sample
Frequency- how often
something occurs
Population genetics
involves studying the
frequency with which
certain alleles occur in a
population’s gene pool
In 50 years, will the 
allele frequencies be the
same?
Hardy-Weinberg
• Hardy-Weinberg Equilibrium Principle – frequencies
of the dominant and recessive alleles in a population
change in time due to 5 things:
• Mutations
• Migration
• Natural selection (survival of fittest)
• Small population
• Non-random mutation
• If these things occur, then the frequencies change
and a population evolves
Quiz
______________=the genetic change of
populations over time.
_____________ =group of organisms of
the SAME species that occupies certain
area.
_____________=organisms that can
interbreed and produce FERTILE offspring
Quiz
__________=technique uses part of
population to represent whole population.
__________=all of the genes of every
individual in population sample.
• frequencies of the dominant and recessive
alleles in a population change in time due
to 5 things:
• Mutations, Migration, Natural selection, Small
population, Non-random mutation
History of Evolutionary Thought
Before 1850, most people believed…
– Earth formed by supernatural events and never
changed
– Earth only a few thousand years old
– Each species was made to fit its environment
– Species never changed and did not go extinct
Early Scientists’ Ideas
Darwin deserves credit for the Theory of
Evolution as we know it today
He was not the first to come up with the idea:
– Carolus Linnaeus proposed a new system of
organization for plants and animals based on their
similarities (noticed relationships)
– Erasmus Darwin considered how organisms could evolve
through mechanisms such as competition
– Jean-Baptiste Lamarck presented evolution as occurring
due to environmental change over long periods of time
Carolus Linnaeus
Developed a classification
system for the huge variety of
living things he found
– Wrote book Systema Naturae
in 1735 to reveal his
classification system
– There are currently 1.9 million
species that have been
identified using his method
– Linnaeus’s system of classification
reflects evolutionary relationships
Jean Baptiste Lamarck
–
–
–
–
A French naturalist who proposed that
populations of species evolve
His idea proposed:
Changes in an environment cause an
organism’s behavior to change, leading to
greater use or disuse of a structure or organ.
The organism would pass on these acquired
changes to its offspring, so a species would
change in time.
Idea called “Evolution by inheritance of
acquired characteristics”
Wrong on several accounts
Charles Darwin
At 22, was invited to sail on the
“HMS Beagle”
– Was going to school to be a
minister-believed God created
each species to match its habitat
and they never changed.
– Thought Earth was about 6,000
years old and didn’t change, just
like everyone else.
Darwin’s Observations
One place of note that
he visited was the
Galapagos Islands
During journey, he made
observations and
recorded them in a
journal.
Darwin observed fossil
and geologic evidence
supporting an ancient
Earth.
Darwin’s Finches
When Darwin traveled to the Galapagos he
took interest in the finches
He noticed the finch species on the islands
were different, but all resembled one from S.
America.
Darwin thought some migrated and new
species evolved.
Darwin’s Finches
This is what Darwin
proposed:
– Finches migrated from
South America to the
islands.
– Populations on different
islands adapted to
different environments and
food sources they found.
– Those that could survive
passed on their genes.
– Those that couldn’t survive
perished.
Darwin’s Finches
Over time different
mutations accumulated
in the different finch
populations on the
different islands.
The populations
diverged, or became
more and more
different from each
other.
Darwin’s Finches
The populations on the islands became so different
they no longer mated if they met
Several new finch species evolved from a common
ancestor from S. America
This is an example of macroevolution.
Recent finch
research
Speciation
Geographical isolation- members of a population
are separated geographically
– Major step that leads to speciation
– Due to volcanoes, earthquakes, flooding, etc.
– Can lead to divergence and then speciation
Artificial Selection
Artificial selection- human intervention in animal or
plant reproduction to ensure that certain desirable
traits are passed on
Instead of NATURE selecting which traits are
favorable, HUMANS selectively breed those animals
with favorable traits
Ex. dogs or racehorses
Darwin bred pigeons to
explore this idea.
Darwin’s Results
In 1859, Darwin published The
Origin of Species
His book stirred up controversy
Idea called “Evolution by natural
selection”
Darwin Video
Darwin’s Book Explained Natural
Selection
Natural selection- organisms best suited to
their environment survive and reproduce
–
–
–
Darwin’s proposed mechanism of evolution
Survival depends on the particular environmental
conditions a species finds itself in—nature!
If the environment changes, so do the populations
that live there
Adaptation- using inherited genetic
characteristics to increase chance of survival
in new environment
Natural Selection and Salamanders
Natural Selection
Three conditions necessary for natural
selection to occur:
– Genetic variation: Individuals within a
population must be genetically different
****Random mutations are the raw material for
evolution to occur!!!!!!!
– Overproduction of offspring: More organisms
are born than can survive
– Differential reproduction: Certain traits enable
individuals to survive and have more offspring
than others
Result of Natural Selection
- Genes that help a population survive in their
conditions stay in their gene pool, while
“unfavorable” genes gradually decrease in
frequency
- This causes changes in the genetics of
populations EVOLUTION!!!!!
- As new mutations accumulate over a long time,
the new populations no longer can mate with the
original they started as. New species have
formed!
Whose idea for
evolution is this?
Types of Evolution
Evolution - genetic change of a population of
organisms over time descent with modification
Microevolution:
Small genetic changes of a population
Shorter amount of time
Peppered moth simulation was
microevolution
Types of Evolution
MACROevolution-When
new species are formed
over long periods of time
– Due to tremendous
amounts of
accumulated genetic
changes in a
population
– Speciation- formation
of new species due to
accumulated
microevolution and
mutations
EVOLUTION
by natural selection
Microevolution
Changes
in gene frequencies
in a population
Shorter times
Examples:
Peppered moth
and Bengal tiger
MACROevolution
Accumulated
microevolution and
mutations to form
whole new species
Longer times
Examples:
Darwin’s finches and
geographical isolation
Evidence for Evolution
Three types of evidence:
– Fossils
– Anatomical
– Molecular
Fossil Evidence
•
Transitional species- species that have
been found in the fossil record that are
intermediates between two other species
in the evolutionary process
–
–
Radiometric dating- a dating technique that
measures amount of radioactive material in a rock
or fossil
Relative dating- a dating technique that estimates
the date of a fossil by relating it to the age of the
layers of rock around it
Fossil Evidence
• To fossilize an
organism must be
buried by sediment
– In swamps, mud, tar
pits, or the ocean
bottom
– Hard stuff fossilizes
(bones, nails)
– Radiometric and
relative dating are
used to find out how
old the fossil is
Relative
Dating
Radiometric
Dating
Fossil Evidence
•
Fossils show:
–
–
Life has been around for millions of years
Transitional species link older to newer species
– Darwin proposed the idea of transitional species,
though he had no evidence
– Today we have evidence:
• Archaeopteryx
• Tiktaalik Fossil, etc.
• Whales
Anatomical Evidence
• Anatomical evidence- evidence for evolution
which is based on similarities and differences
between the physical structures of different
species.
• What can we tell about the relatedness of the
three species below?
Anatomical Evidence
• Homologous structures- structure is the
same (homo) but not function
–Bird wing, dolphin fin, and a human arm
–Function these structures is not the same!
–Show that these species shared a common
ancestor
–Similar structures resulted from accumulated
mutations and modifications
Homologous Structures
Anatomical Evidence
• Analogous structures- structure different but serve
the same function
–Function = flight
–Butterfly wing, bat wing, fly wing
 These structures, although they have the same
function, are not built the same! similar functions
 similar external form
 different internal structure & development
 different origin
 no evolutionary relationship
Analogous structures
Don’t be fooled
by their looks!
Solving a similar problem with a similar solution
Anatomical Evidence
Anatomical Evidence
•
Vestigial structuresstructures that no
longer serve a function
• These structures are
the remnants of an
evolutionary past and
show common anatomy
with other species
Molecular Evidence
•
Molecular evidenceevidence concerning the
comparison of DNA and
protein molecules between
species
• Ultimate tools for
scientists studying
evolution
• Same genetic basis
for all organisms: A,
C, T, and G shows we
are all related
Molecular Evidence
• Mutations and sexual
reproduction are a cause of
variation in a species’ DNA
• DNAmRNAprotein
– Transcription- copying the DNA
code into mRNA
– Translation- converting the code
of mRNA into a long chain of
amino acidsprotein
– Differences in DNA are seen in
differences in protein and
therefore, traits
Molecular Evidence
• Species with more similar DNA
are more closely related on the
evolutionary tree
– Less time since they
split to accumulate
mutations (and,
therefore, differences)
– Common ancestorany species in the
past from which two
or more related
species has evolved
– Evidence for Evolution
= speciation event
= mutation
How did life begin?
1.)Extraterrestrial origin (Big
Bang Theory)
2.)Creation—”divine forces”
3.)From non-living matter
(“Chemical Evolution”)-Organic compounds
assembled creating 1st
bacterial cell
How Modern Day Biologists
Classify
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•
•
•
1. Comparing anatomy (physical traits)
2. Looking at genetic similarities & differences
3. Biochemical make-ups
4. Behavioral similarities
Origin of Life Video
Cladograms
• Cladogram- a branching diagram that shows
evolutionary relationships
• We use taxonomy – the science of classifying
living things, to help us determine the
cladogram