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Chapter 15 Evolution
Section 1: Darwin’s Theory of Natural Selection
Section 2: Evidence of Evolution
Section 3: Shaping Evolutionary Theory
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• Evolution of the Cell phone
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Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Darwin on the HMS Beagle
 Darwin’s role on the ship was as naturalist
and companion to the captain.
 His job was to collect biological and geological
specimens during the ship’s travel.
 Who was Charles Darwin
• Charles Darwin was a major pioneer in
Biology!
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
The Galápagos Islands
 Darwin began to collect mockingbirds, finches,
and other animals on the four islands.
 He noticed that the different islands seemed
to have their own, slightly different varieties
of animals.
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
 Almost every
specimen that
Darwin had
collected on the
islands was new
to European
scientists.
 Populations from the mainland changed after
reaching the Galápagos.
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Darwin Continued His Studies
 Darwin hypothesized that new species could
appear gradually through small changes in
ancestral species.
 Darwin inferred that if humans could change
species by artificial selection (the process of
selective breeding of organisms to produce
offspring with desired characteristics ), then
perhaps the same process could work in
nature.
 Video
• NOVA – The eye
3 examples of Natural Selection
• Variation in Nature
– Darwin pointed out that in Nature inherited variation was
common
• Struggle for Existence
– Darwin realized that high birth rates and a shortage of life’s
basic needs forced organisms into a constant struggle for
existence
• Natural Selection
– Darwin proposed that generation after generation, the
struggle for existence selects the fittest individuals to
survive in nature
– Video
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Natural Selection
 Individuals in a population show variations.
 Variations can be inherited.
 Organisms have more offspring than can survive
on available resources.
 Variations that increase reproductive success will
have a greater chance of being passed on.
 Bird of paradise
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
The Origin of Species
 Darwin published On the Origin of Species by
Means of Natural Selection in 1859.
 Darwin’s theory of natural selection is not
synonymous with evolution.
 It is a means of explaining how evolution works.
• Evolution of Dance
Charles Lyell
• Darwin studied Lyell’s work while on the
Beagle
• Lyell put forth arguments that the Earth was
older than people originally thought
• Today's accepted age of the Earth of 4.55
billion years was determined by C.C.
Patterson using Uranium-Lead dating on
fragments of the Canyon Diablo meteorite
and published in 1956
KT Boundary
Lyell
– He argued that the
modern world must have
been shaped by the
same geological forces
that can be seen in action
today
• EX: erosion in river
valleys, volcanic
eruptions, earthquakes
– If Earth can change
over time, why not the
life on Earth as well?
Chapter 15
Evolution
15.2 Evidence of Evolution
Support for Evolution
 The fossil record
 Fossils provide a record of species that lived long ago.
 Fossils show that ancient species share similarities
with species that now live on Earth.
Glyptodont
Armadillo
• Tiktaalik – Intermediate Species?
• Fossil Finding
• LETS FIND SOME FOSSILS
Fossils
• Sometimes Geologic processes such as
earthquakes etc. can thrust up fossils that
formed under ancient rivers, oceans and
lakes so that they reside on dry land OR
– These bodies of water can dry up over time so
that fossils are accessible
• Petoskey stones
Fossils
• Layers of rock from 3 billion
years ago often contained
fossils
• They are commonly found in
sedimentary rocks
– Form when silt, sand or clay
builds up in the bottom of a
river, lake or ocean
– As sediments pile up,
pressure on the lowers layer
turn them into rocks such as
sandstone or limestone
• Layers like a cake
Relative Dating
• Each layer has it’s own time period in history
– The hard pieces such as teeth and bone are preserved
• Each fossil appears at one time and disappears at
another
– Scientists can distinguish groups of fossils in specific rock
layers
– These rock layers can be arranged in Chronological (Time)
order to compare the ages of the fossils found in one layer
to another layer
• RELATIVE DATING-not exact
Absolute/Radioactive Dating
• How do scientists calculate the age of the
Earth?
– 100 Years ago Scientists discovered that certain
elements are radioactive (they break down from
an unstable form to a more stable form over time.
• Measured in a unit called Half-Life
• Act as a series of clocks by which they can measure
the age of rocks
– After 1 million years, ½ of a sample may be still radioactive
– After 2 million years, ¼ of the same sample = radioactive
– After 3 million years, 1/8 ……..and so on!
Absolute/Radioactive Dating
• Carbon-14 is a Radioactive element we take
in from the atmosphere
• When an organism dies-stops taking in C-14
– Half life=5770 years
• At the end of 5770 years, half of C-14 is
converted into Nitrogen-14=more stable
– By comparing the Carbon-14 to the Nitrogen-14
scientists can estimate the age of the fossil
• Absolute Dating
• This is how the Geologic Time Scale came about!!
Cambrian Explosion
Chapter 15
Evolution
15.2 Evidence of Evolution
 Derived traits are newly evolved features,
such as feathers, that do not appear in the
fossils of common ancestors.
 Ancestral traits are more primitive features,
such as teeth and tails, that do appear in
ancestral forms.
 Anatomically similar structures inherited from
a common ancestor are called homologous
structures.
 They have similar structures and different functions (bat wing and
human hand)
Reptile or Bird?
• Archaeopteryx
• The name Archaeopteryx means ‘ancient wing’, and this animal may
be the most famous fossil find of all time. Archaeopteryx was thought
to have been the first known bird until the discovery of Protoavis in
1986. It was larger than a crow and had sharp teeth, a long bony tail
and three clawed fingers. Although Archaeopteryx could probably fly
a few feet, it was not capable of flight like a true bird. Archaeopteryx
lived in the Late Jurassic period, and specimens have been found in
limestone deposits in Bavaria, West Germany. The first specimen
was discovered in 1861, and since then six skeletons have been
found.
Legs on a snake?
Ajolote Mexican Mole Lizard
Archaeopteryx
Homologous Structures
Chapter 15
Evolution
15.2 Evidence of Evolution
Vestigial Structures
 Structures that are the
reduced forms of
functional structures in
other organisms.
 Evolutionary theory
predicts that features of ancestors that no
longer have a function for that species will
become smaller over time until they are lost.
(tail bone, wisdom teeth, baby toe?!)
Chapter 15
Evolution
15.2 Evidence of Evolution
 Analogous structures can be
used for the same purpose
and can be superficially similar
in construction, but are not
inherited from a
common ancestor.
 Show that
functionally similar
features can evolve
independently in
similar environments
Chapter 15
Evolution
15.2 Evidence of Evolution
Comparative Embryology
 Vertebrate embryos exhibit homologous
structures during certain phases of
development but become totally different
structures in the adult forms.
Review
What type of animal is this?
Homologous or analogous?
Chapter 15
Evolution
15.2 Evidence of Evolution
Comparative Biochemistry
 Common ancestry
can be seen in the
complex metabolic
molecules that many
different organisms
share.
Chapter 15
Evolution
15.2 Evidence of Evolution
 Comparisons of the similarities in these
molecules across species reflect evolutionary
patterns seen in comparative anatomy and in
the fossil record.
 Organisms with closely related morphological
features have more closely related molecular
features.
So in Summation…..
• Evolution is based on scientific discovery
and facts!
– Fossils
– Comparative Anatomy
– Biochemistry
– Embryology!
• Stop 3/19
Gene Pool
• Sum of all Genes in a population
– The population evolves not the individual!
• A population in which the frequency of
alleles (form of a gene) does not change
from generation to generation it is said to be
in:
– GENETIC EQUILIBRIUM
Common Descent
• Darwin further argued that just as each living
organism is the descendant of its parents
and grandparents
• Each living species has descended from
other living species over time
– COMMON DESCENT
Altering the Genetic Equilibrium
• Genetic Drift: alteration
of allelic frequencies
by chance processes
– Amish population – its
possible that in a small
population, a larger
population will inherit
recessive alleles for
shorter arms or legs, or
dominant alleles for
extra fingers and toes
Altering the Genetic Equilibrium
• Reproductive Isolation:
preventing formally
interbreeding organisms
from producing fertile
offspring
– Tree Frogs – If one group
evolves the behavior of
mating in the fall while another
mates in the spring….they will
be reproductively isolated
Species diversify when introduced
into new Environments!
• The process of
Evolution of an
ancestral species into
an array of species
that occupy different
niches is called
– ADAPTIVE RADIATION
– Just like the Finches!
Adaptive Radiation is an Example of
Divergent Evolution
• Divergent Evolution
– The pattern of evolution in which
species that once were all similar to
the ancestral species become more
and more distinct
• Species begin to adapt to
different environmental
conditions and change according
to the pressures of Natural
Selection
• Ring Species
Counterpart to Divergent Evolution
• Convergent
Evolution!!!!
• The pattern of
evolution in which
distantly related
organisms evolve
similar traits!
• EX: Fins!
EVIDENCE OF EVOLUTION
• FOSSILS
• ANATOMY
– HOMOLOGOUS STRUCTURES
– ANALOGOUS STRUCTURES
– VESTIGIAL STRUCTURE
– EMBRYOS
http://evolution.berkeley.edu/evolibrary/home.php
WHAT IS ANOTHER EXAMPLE OF
VESTIGIAL STRUCTURES?
OTHER EVIDENCE OF EVOLUTION
• FOSSILS
• ANATOMY
– HOMOLOGOUS STRUCTURES
– ANALOGOUS STRUCTURES
http://evolution.berkeley.edu/evolibrary/home.php
OTHER EVIDENCE OF EVOLUTION
• FOSSILS
• ANATOMY
– HOMOLOGOUS STRUCTURES
http://evolution.berkeley.edu/evolibrary/home.php
OTHER EVIDENCE OF EVOLUTION
• FOSSILS
• ANATOMY
– HOMOLOGOUS STRUCTURES
– ANALOGOUS STRUCTURES
– VESTIGIAL STRUCTURE
– EMBRYOS
• BIOCHEMISTRY
– WHAT 2 THINGS?
http://evolution.berkeley.edu/evolibrary/home.php
EVIDENCE OF EVOLUTION
• STRUCTURAL ADAPTATIONS
– MIMICRY
– CAMOUFLAGE
– Chameleon
http://evolution.berkeley.edu/evolibrary/home.php
http://science.howstuffworks.com/animal-camouflage2.htm
Chapter 15
Evolution
15.2 Evidence of Evolution
Types of Adaptation
 An adaptation is a trait shaped by natural
selection that increases an organism’s
reproductive success.
 Fitness is a measure of the relative
contribution an individual trait makes to the
next generation.
Chapter 15
Evolution
15.2 Evidence of Evolution
Mimicry
 One species evolves to resemble another
species.
Western coral snake
California kingsnake
Chapter 15
Evolution
15.2 Evidence of Evolution
Camouflage
 Allows organisms to
become almost
invisible to predators
Leafy sea dragon
Camouflage Video
• Video
• The secret behind (octopuses') color capability is special
skin cells called chromatophores.
– Each chromatophore consists of three bags of pigment.
– By squeezing or expanding the bags, octopuses can change the color
displayed by each cell, allowing millions of subtle combinations.
– Since each cell is controlled separately, they can create remarkably
sharp displays. In addition, reflective coatings under the cells help
enhance the effect.
– Taken by Jerry Michalski
Cuttlefish Camo
New York Times
• Video
Decorator Crab
Decorator Crab
• Nat Geo Video – Decorator crab
Camouflage – blending in
How has predation influenced evolution?
Adaptations to avoid being eaten:
spines (cactii, porcupines)
hard shells (clams, turtles)
toxins (milkweeds, some newts)
bad taste (monarch butterflies)
camouflage
aposematic colors
mimicry
Aposematic colors – warning
Is he crazy???
Mimicry – look like something that is dangerous
or tastes bad
Mimicry – look like something that is dangerous
or tastes bad
Mullerian mimicry – convergence of several
unpalatable species
Mimicry – look like something that is dangerous
or tastes bad
Batesian mimicry – palatable species mimics an
unpalatable species
model
mimics
mimic
model
Chapter 15
Evolution
15.2 Evidence of Evolution
Consequences of Adaptations
 Some features of an organism might be
consequences of other evolved characteristics.
 They do not increase reproductive success.
 Features likely arose as an unavoidable
consequence of prior evolutionary change.