One of the most respected evolutionary biologists has defined biological
evolution as follows:

"In the broadest sense, evolution is merely change, and so is allpervasive; galaxies, languages, and political systems all evolve.
Biological evolution ... is change in the properties of populations of
organisms that transcend the lifetime of a single individual. The
ontogeny of an individual is not considered evolution; individual
organisms do not evolve. The changes in populations that are
considered evolutionary are those that are inheritable via the genetic
material from one generation to the next. Biological evolution may be
slight or substantial; it embraces everything from slight changes in the
proportion of different alleles within a population (such as those
determining blood types) to the successive alterations that led from the
earliest protoorganism to snails, bees, giraffes, and dandelions."
- Douglas J. Futuyma in Evolutionary Biology, Sinauer Associates 1986
Evolution and Populations

It is important to note that
biological evolution refers to
populations and not to
individuals and that the
changes must be passed on
to the next generation. In
practice this means that
evolution is a process that
results in heritable changes in
a population spread over
many generations.
Competing Theories
Lamarck’s Theory of Evolution
Proposed in 1809, Lamarck
observed that characteristics of
living things could change over
time.
For example, if muscles are used,
they grow stronger. These are
called “acquired” characteristics.
Competing Theories
Lamarck’s Theory of Evolution
Lamark proposed that organisms can pass on these acquired
characteristics to their offspring.
For example: ancestors of Giraffes had short necks. Lamark’s
theory goes that since they had to stretch to get food, their necks
became longer and they could pass this trait to their offspring.
Competing Theories
Darwin and Wallace’s theory of Natural Selection would have explained the giraffe’s
long necks in the following way:
• An original group exhibited variation in neck length.
• Longer necks were more successful in the given
environment.
• Longer necked giraffes were then able to reproduce more
often than shorter necked giraffes and thus pass on their
long neck genes to the next generation.
• After many generations, the population has a general
increase in neck length.
Competing Theories
Even though the giraffe's neck
is extremely long, it has only
seven neck vertebrae, the
same number that people and
most other mammals have.
Definition of Evolution:
The accumulation of changes
in the heritable
characteristics of a
population.
Evolution describes the
changes in the various genes
of a species over time.

These changes are the
result of:
 Mutations
 Natural selection
 Chance
Voyage of the Beagle, 1831-1836
Succession of Types
Why should extinct armadillo-like species and
armadillos be found on the same continent?
The changes imply ancestry!
“This wonderful relationship in the same continent
between the dead and the living will, I do not doubt,
throw more light on the appearance of organic beings
on our earth, and their disappearance from it, than any
other class of facts.”
--The Voyage of the Beagle, ch. 8
Basic Tenets of the
Theory of Evolution:
1.
Populations tend to produce more
offspring than the environment can
support.
•
This leads to a struggle for existence in which
some individuals survive and some die.
Carrying Capacity
2. Natural Selection


Definition:
 The over-production of
offspring leads to
competition and survival of
the individuals best suited
to that particular
environment.
The better adapted
individuals tend to survive
and reproduce more than the
less well-adapted individuals.
3. The variation in individuals in a population is controlled by
their genes and is therefore inheritable.
 The better adapted individuals pass on their
characteristics to more offspring than the less well
adapted.
 The results of natural selection therefore accumulate.
 As one generation follows another, the characteristics
of the species gradually change.
How Does Variation Arise?
In the DNA:
-Sexual Reproduction
-Mutations
In the Environment:
-Genetic Drift
Sexual Reproduction

Role:
 Promotes variation in a species through
meiosis and fertilization which is
essential to natural selection.
Meiosis:

Crossing over and
random separation of the
homologous pairs of
chromosomes during
Meiosis.
resulting in a
gamete that is a
mixture of paternal
and maternal
chromosomes.
Crossing Over
Fertilization:
 Two
gametes
from different
individuals fuse
to create a new
organism,
leading to further
variation
Mutations:
Mutations:
Changes in the base pair sequence
of DNA.
Most are neutral or harmful to the
organism, but some have positive
effects.
Note: In an organism that sexually
reproduces, the mutation must
occur in a gamete (sex cell) if it is
to be passed on to offspring, and
thus contribute to the evolution of
that organism.
A mutation has caused the garden moss
rose to produce a flower of a different color.
Variation is non-directional (random)
The selection process is
directional:
It is dictated by the environment
(not random).

This leads to differential survival:
 The result is that the individuals
best adapted to a specific
environment will survive to
reproduce.
○ They will get the most food
○ find the best shelter
○ find a mate
○ reproduce and care for their
offspring
○ not be eaten by other species.
Differential Survival:

If environments change
(either gradually or
suddenly), the “best
adapted” may also
change.

This process can lead to
changes in the species
Genetic Drift:
Sometimes the
frequency of a gene
in a population is
determined by
chance and not by
whether it gives the
individual an
advantage in the
environment.
 This is known as
genetic drift.

Populations:

It is important to
know at this point
that evolution
doesn’t work on the
level of individuals or
species- it works on
the level of
populations.

In other words:
individuals do not
evolve, populations
do.
Speciation
When two groups of
a species are in
different
environments they
cannot interbreed.
 If the selection
pressure is different,
they will eventually
become different
species: aka
speciation.




The eastern meadowlark
(Sturnella magna) and the
western meadowlark (Sturnella
neglecta) have very similar
body shapes and coloration.
Their ranges overlap in the
middle of the country.
Considered different species:
 Songs are different
 Behavioral differences that
prevent interbreeding.
In the summer of 1995, at least 15 iguanas survived Hurricane Marilyn on a raft of
uprooted trees. They rode the high seas for a month before colonizing the Caribbean
island, Anguilla. These few individuals were perhaps the first of their species, Iguana
iguana, to reach the island.
Speciation:
Artificial Speciation
Allopatric speciation of squirrels in the Grand Canyon
Harris’s antelope
squirrel (south rim)
White-tailed
antelope squirrel
(north rim)
Ex. Many of the finches in the Galapagos
islands.
Why are finches different on different
islands?
Islands have different
kinds of seeds available
which select for different
types of beaks to eat
them.
 In time the birds become
so genetically/physically
different they cannot
interbreed.

Environments constantly change and if a
species cannot adapt, they may go extinct.
Ex. Dinosaurs
Couldn’t adapt
to colder climate
 Their place was
taken by mammals
(homeothermicwarm blooded)
 Not all dinosaurs
went extinct.
Some also
evolved to
become warmblooded birds.

There have been 5 major extinction events
during the history of life on Earth.
Some 99.9% of all species that have
ever lived on Earth are now extinct.
The CretaceousTertiary Extinction
(65.5 MYA) is
probably the most
well known, as it
killed off all nonavian dinosaurs. 75%
of all species went
extinct.
There have been 5 major extinction
events during the history of life on
Earth.
This wasn’t even the largest though. That honor goes to the PermianTriassic Extinction (251 MYA) which caused the extinction of 96% of all
marine species and 70% of all land species.
Examples of
Evolution:
Archeopteryx: A transition fossil between
reptiles and birds.
Example #1: Peppered Moths

A famous example from England that demonstrates natural
selection is the Pepper Moth.
 Two different species of moths, one light colored and one dark.
○ Before the 1850’s the dark one was very rare, after the 1850’s the
light color became rare.
What happened in the 1850’s?
INDUSTRIAL REVOLUTION
Coal fired plants produced lots
of soot that covered the trees
and buildings, making everything
dark. So where once the birds
preferentially picked off and ate
the dark moths, they now saw
and ate the light ones instead.
Example #2: Resistance of Bacteria to
Antibiotics Through Exposure

As the use of
antibiotics have
become widespread
 many disease-causing
bacteria have
developed resistance
against known
antibiotics.
 Only the resistant
bacteria will survive
and reproduce
 This
means that if
you become
infected with
these bacteria,
treatment with
antibiotics will not
cure you and the
disease may
become fatal.

This is more likely to occur when a small
dose of antibiotics is used over a short time.
 It will kill some of the bacteria but not all.
 Next time antibiotics are used, these bacteria may
be less vulnerable and more survive.
 Repeated small dosages can produce very
resistant strains.
http://www.usatoday.com/story/news/nation/2013/03/05/
superbugs-infections-hospitals/1965133/

In the USA,
 half the livestock is fed
antibiotics to increase the
growth of the animals.
○ This leads to strains of
antibiotic resistant bacteria
being discovered in the gut
of these animals and then in
human guts.
○ The runoff from the waste
and feed contains the
antibiotic resistant strains
that can get out to the rest of
the world.
Example #3: Artificial Selection
Example #3: Artificial Selection
 There
are numerous examples of
humans performing their own type of
selection (hence: artificial) on
desired, heritable traits belonging to
a variety of organisms.
Since we seem to like the #3,
we have…
3 examples:
Example #3: Artificial Selection
#1:
The domestication of the wolf (or
domestication of any animal) is a
good example:
Further selection of favored
traits resulted in the varied
amount of dog breeds we have
today.
Example #3: Artificial Selection
#2:
Selective breeding
transformed teosinte’s few
fruitcases into modern
corn’s rows of kernels.
Example #3: Artificial Selection
#3:
By selecting various traits of the common wild mustard
plant to breed for, we have created many common
vegetables we use today such as broccoli, cauliflower and
brussels sprouts.
Example #3: Artificial Selection
Artificial selection is also important as it acts
as an experiment on natural selection.
Experimentation is the ultimate test of a
scientific hypothesis, without it you can never
be sure that a correlation (i.e. the environment
selecting for traits) you observe is significant.
Example #3: Artificial Selection
In artificial selection, humans
are the manipulators (we are
the environment)- we choose
which individuals get to
reproduce.
We would expect to see
what is found in nature- that
the individuals who
reproduce pass on their
genes/traits, and that is
exactly what we see.
Example #3: Artificial Selection
Artificial Selection can also be used as
evidence of evolution.
We will discuss more forms of evidence next.
Scientific Evidence
for Evolution
“Those who cavalierly reject the Theory of
Evolution, as not adequately supported by facts,
seem quite to forget that their own theory is
supported by no facts at all”
-Herbert Spencer, Essay Scientific,
Political and Speculative, 1891.
Fossils!
Fossils do show intermediate
stages, despite their rarity.
And geological strata consistently
reveal the same sequence of
fossils!
A quick and simple way to debunk
the theory of evolution would be to
find a fossil horse in the same
stratum as a trilobite.
Fossils!
For example, there are
now at least eight
intermediate fossil
stages identified in the
evolution of whales.
Vestigial Structures

An organ present in the organism but either
reduced in size or has no use.
Ex.
 Femur in some whales
 Dewclaw in dogs
 Eyes in blind mole rats
 Fake sex in virgin Whiptail lizard
 Wings on flightless birds
Human Vestigial Organs
The Appendix
Human Vestigial Organs
Wisdom Teeth
Human Vestigial Organs
Human Coccyx (Tailbone)
Human Vestigial Organs
Body Hair and Erector Pili (Goosebumps)
Human Vestigial Organs
Ear Muscles
Human Vestigial Organs
Third Eyelid
Scientific Evidence

Homologous Structures
 Similar structures in very different organisms is
evidence of a common ancestor.
An example of this is the
similarity of the skeleton
between all mammals.
Every bone in a bat has is
its own identifiable
counterpart in a human.
Identifiable, because of
the order in which they
join up. Only the
proportions are different.
from Ernst Haeckel's 1904 work
Kunstformen der Natur
Scientific Evidence

Embryonic
Development
 Physical similarities
between embryos of
different species at
different stages.
In 1866, Ernst Haeckel
proposed his theory that
the embryonic
development of an
individual organism
followed the same path
as the evolutionary
history of its species.
Scientific Evidence
Haeckel’s theory has
largely been rejected
today.
Though humans share
common ancestors
with other animals,
stages of human
embryonic
development are not
functionally equivalent
to the adults of these
shared ancestors.
In other words, just because
we develop a tail and gill slits
embryonically does not mean
that they are functional like
they are in fish.
Scientific Evidence
Darwin's view: that early
embryonic stages are
similar to the same
embryonic stage of
related species but not
to the adult stages of
these species, has
been confirmed by
modern evolutionary
developmental biology
Scientific Evidence

Similarity of Genetic
Code (DNA)
 All organisms share
the same genetic
code, based on the
series of bases: A, T,
G, and C.
 The more similar two
species are the more
alike the sequence of
bases in their DNA
are.
Common
Misconceptions
#1:
Isn’t evolution just a theory that
even scientists can’t agree on?
First we need to look at what the word theory means.
The Oxford English Dictionary gives two meanings:
Theory, Definition 1: A scheme or system of ideas or statements held
as an explanation or account of a group of facts or phenomena; a hypothesis
that has been confirmed or established by observation or experiment, and is
propounded or accepted as accounting for the known facts; a statement of what
are held to be the general laws, principles, or causes of something known or
observed.
Theory, Definition 2: A hypothesis proposed as an explanation; hence,
a mere hypothesis, speculation, conjecture; an idea or set of ideas about
something; an individual view or notion.
#1:
Isn’t evolution just a theory that even scientists can’t agree on?
Darwin’s Theory, as with all scientific theories follow the first definition.
Having your explanation for a group of observations being called a theory is an
honor in the scientific field; it means that it is the best explanation we have for
why something happens.
Does being a scientific law mean you have more evidence to support your
explanation than a theory?
Not at all… laws and theories are used to describe different things in science.
In general, Scientific Laws describe what is happening. Examples include:
Newton’s Laws of Gravity, Kepler’s Laws of Planetary Motion, Law of
Conservation of Energy, Laws of Thermodynamics….
Scientific Theories explain why something happens. Examples
include: The Big Bang Theory, Cell Theory, Theory of Relativity, String Theory…
#2:
Was one of my ancestors really a chimpanzee?
NO!
Evolution points to humans sharing a common ancestor with
chimpanzees and other great apes around 7-8 million years ago.
Chimps have continued to evolved alongside us since then.
The ancestor you
share between
yourself and the
chimpanzee at the
zoo probably did look
something like this
though:
Sahelanthropus tchadensis
#2:
Was one of my ancestors really a chimpanzee?
In fact we have shared the Earth with many other human like
species (called hominids).
We even shared the Earth
at
the same time with other
hominid species such as
Homo Neanderthalensis.
And this recent find:
Homo Floresiensis, the
hobbit
people on the island of
Flores
in Indonesia.
Courtesy of Smithsonian, 03/10
#3:
How can natural selection lead to extremely
complicated structures/organs like the human
eye?
Though the eye is incredibly
complex, even Darwin back in his
day saw that the Theory of Evolution
could account for it:
“...if numerous gradations from a perfect and complex
eye to one very imperfect and simple, each grade being
useful to its possessor, can be shown to exist; if further,
the eye does vary ever so slightly, and the variations be
inherited, which is certainly the case; and if any variation
or modification in the organ be ever useful to an animal
under changing conditions of life, then the difficulty of
believing that a perfect and complex eye could be
formed by natural selection, though insuperable by our
imagination, can hardly be considered real”
-Charles Darwin, Origin of Species
#3:
How can natural selection lead to extremely complicated
structures/organs like the human eye?
The first step in the evolution of the eye, would be a set of
photoreceptor proteins that sense light called photoreceptors.
Photoreceptors can sense ambient brightness, and distinguish
light from dark.
These allowed unicellular organisms to move toward where they
sensed light, probably to use for photosynthesis.
Example of a photoreceptor
in a Euglena
#3:
How can natural selection lead to extremely complicated
structures/organs like the human eye?
The next step would be indenting the tissue
behind the eye to make a cup behind the
photoreceptor cells. This enlarges the area of
photoreceptor cells as well, now known as the
retina.
These primitive eyes are called eyespots.
Example of an eyespot in a
planarian (flat worm)
#3:
How can natural selection lead to extremely complicated
structures/organs like the human eye?
The “pinhole camera” eye stage was next. This is where the
eyespot hollows out more and reduces the size of the hole where
the light comes through. This gave the organism true imaging,
allowing for directional and shape sensing.
Example of a pinhole eye in
a nautilus.
#3:
How can natural selection lead to extremely complicated
structures/organs like the human eye?
Next came eyes that were fully enclosed, fluid-filled chambers.
A refractive lens has also evolved over the pin-hole.
Refraction is when light waves change speed as they enter a
new medium. This bends the angle of the light, and in the case of
an eye (or camera) directs the light into a single beam on one
spot.
The refractive lens in most
animals is known as the
cornea.
The iris later evolved, which
allows the organism to
adjust the “pin-hole”,
controlling the amount of
light that enters the eye.
#3:
How can natural selection lead to extremely complicated structures/organs like the human
eye?
So if we remember that evolution is an accumulation of heritable
changes, the evolution of complex structures like they eye, though
remarkable, isn’t all that unrealistic.
“Thus, from the war of nature, from famine and
death, the most exalted object which we are capable
of conceiving namely, the production of the higher
animals, directly follows. There is grandeur in this
view of life, with its several powers, having been
originally breathed into a few forms or into one; and
that, whilst this planet has gone on cycling on
according to the fixed law of gravity, from so simple a
beginning endless forms most beautiful and most
wonderful have been, and are being, evolved.”
-Charles Darwin, On the Origin of Species