EVOLUTION
Chapter 15
What is evolution?
A basic definition of evolution…
“…evolution can be precisely defined as any
change in the frequency of alleles within a
gene pool from one generation to the next."
- Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989
Worth Publishers, p.974
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So what does the definition
mean?
Evolution is a change in the number of
times specific genes that code for specific
characteristics occur within an interbreeding
population
 Individuals don’t evolve, populations do
 There is no implied “improvement” in
evolution

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So what does the definition
mean?
Things don’t change because organisms
want or need them to (Lamarkism)
 There is no difference between
macroevolution and microevolution.
Macroevolution is merely a collection of
microevolution events.

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Definition problems

Part of the problem is
that a number of
different definitions for
evolution can be found
both within and without
the scientific
community. These can
easily confuse
laypeople.
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Definition problems
"evolution: The gradual
process by which the present
diversity of plant and animal
life arose from the earliest and
most primitive organisms,
which is believed to have
been continuing for the past
3000 million years."
-Oxford Concise Science
Dictionary
"evolution: ...the development of a
species, organism, or organ from its
original or primitive state to its
present or specialized state;
phylogeny or ontogeny"
- Webster's
"evolution: ...the doctrine according to
which higher forms of life have gradually
arisen out of lower."
- Chambers
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Definition problems
In addition to being simply
wrong, these definitions can
cause confusion since it is
common for non-scientists to
enter into a discussion about
evolution with such definitions
in mind.
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Charles Darwin
Darwin’s Theory of Evolution

Evolution, or change over time, is the
process by which modern organisms have
descended from ancient organisms.

A scientific theory is a well-supported
testable explanation of phenomena that have
occurred in the natural world.
Voyage of the Beagle
Voyage of Beagle
Dates: February 12th, 1831
 Captain: Charles Darwin
 Ship: H.M.S. Beagle
 Destination: Voyage around the world.
 Findings: evidence to propose a
revolutionary hypothesis about how life
changes over time

The Galapagos Island

Darwin was fascinated in particular by the land
tortoises and marine iguanas in the Galápagos.

Giant tortoises varied in predictable ways from
one island to another.

The shape of a tortoise's shell could be used to
identify which island a particular tortoise
inhabited.
Animals
The Journey Home
 Darwin
Observed that characteristics
of many plants and animals vary
greatly among the islands
 Hypothesis:
Separate species may
have arisen from an original ancestor
Evolution as a Theory AND Fact
•
•
•
Confusion sometimes arises as to whether
Evolution is a theory or a fact. Actually it is both!
The theory of Evolution deals with how
Evolution happens. Our understanding of this
process is always changing.
Evolution is also a fact as there is a huge amount
of indisputable evidence for its occurrence.
A brief history of evolution
Contrary to popular
belief, Darwin was not
the first person to
describe the concept of
evolution, but he was the
one who gave it its
driving force.
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Darwin presumed that populations of individuals
changed over time, and, in 1844, he developed the
concept of the driving force for evolution. It wasn’t
until many years later that he published his idea.
“I have called this principle, by which
each slight variation, if useful, is preserved, by the
term Natural Selection.”
—Charles Darwin from "The Origin of Species“,
1859
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Ideas that shaped Darwin’s
Thinking

James Hutton:

1795 Theory of
Geological change
 Forces change
earth’s surface
shape
 Changes are slow
 Earth much older
than thousands of
years
Ideas that Shaped Darwin’s
Thinking

Charles Lyell

Book: Principles of
Geography
Geographical features
can be built up or torn
down
Darwin thought if
earth changed over
time, what about life?


Lamarck
Lamarck’s Theory of Evolution

Tendency toward Perfection


Use and Disuse


Giraffe necks
bird’s using forearms
Inheritance of Acquired Traits
Lamarck’s Ideas
•
Around 1800, scientists began to wonder whether
species could change or transmute.
•
Lamarck thought that if an animal acquired a
characteristic during its lifetime, it could pass it
onto its offspring.
•
Hence giraffes got their long necks through
generations of straining to reach high branches.
Population Growth


Thomas Malthus19th century English
economist
If population grew
(more Babies born
than die)
 Insufficient living
space
 Food runs out
 Darwin applied this
theory to animals
Controversy!
• Despite the achievement
of scientific consensus on
evolution, some religious
groups continued to
oppose the concept.
Outside the Scopes Trial
• In 1925, the teaching of
evolution was outlawed
in Tennessee, USA,
resulting in the infamous
Scopes Monkey Trial
Basic premises for this discussion
Evolution is not a belief system. It is a
scientific concept.
 Evolution is a theory…but you don’t get
any better than that in science
 There is a lot of contention about evolution,
but not among scientists or scientific
organizations.

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Some basic definitions
Fact: an observation that has been
repeatedly confirmed
 Law: a descriptive generalization about how
the physical world behaves
 Hypothesis: a testable statement that can be
used to build inferences and explanations

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Some basic definitions

Theory: a well-substantiated explanation
that incorporates facts, laws, inferences
and tested hypotheses.
In science, you don’t get any better
than a theory.
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Natural Selection
Observation 1: Organisms generally
have more offspring than can survive
to adulthood.
Observation 2: Offspring are not
identical. There is variation in their
appearance, size, and other
characteristics.
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Natural Selection
Inference: Those organisms that are
better adapted to their environment
have a greater likelihood of surviving
to adulthood and passing these
characteristics on to their offspring.
Survival of the “fittest.”
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Natural Variation & Artificial
Selection

Natural variation--differences among
individuals of a species

Artificial selection- nature provides the
variation among different organisms, and
humans select those variations they find
useful.
Observation and Inference
Let’s do a little exercise…
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Dinosaur tracks are
common occurrences in
the southern and eastern
U.S.
Here is a section of tracks
that were recently
uncovered. Can you
answer the following
questions?
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•What is the size and
nature of the organisms?
•Were the tracks made at
the same time?
•How many animals were
involved?
•Can you reconstruct the
events that occurred?
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•In what direction did the
animals move?
•Did they change speed
or direction?
•Was the soil moist or
dry?
•In what type of rock
were the prints made?
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The following summer
some more digging
revealed more of the
track. What additional
information have you
gained that allows you to
refine your answers?
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•Were the tracks made at
the same time?
•How many animals were
involved?
•Can you reconstruct the
events that occurred?
•In what direction did the
animals move?
•Did they change speed
or direction?
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In the final summer of
the excavation one last
part of the footprint trail
was uncovered. Does this
section provide additional
information to refine
your hypothesis?
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So what happened?
What part of your
hypothesis is
observation?
What part is
inference?
What part is guess?
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This is how science is
done.
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Evolution by Natural Selection

The Struggle for Existence-members of
each species have to compete for food,
shelter, other life necessities

Survival of the Fittest-Some individuals
better suited for the environment
Struggle For Existence &
Survival of The Fittest
Descent


Descent with Modification-Each living organism has
descended, with changes from other species over time
Common Descent- were derived from common ancestors
Evidence of Evolution

The Fossil Record

Geographic Distribution of Living Things

Homologous Body Structures

Similarities in Early Development
Evidence for Evolution




The Fossil RecordLayer show change
Geographic
Distribution of Living
Things
Homologous Body
Structures
Similarities in Early
Development
Evidence of Evolution




The Fossil Record
Geographic
Distribution of
Living Things-similar
environments have
similar types of
organisms
Homologous Body
Structures
Similarities in Early
Development
Homologous Structures
 Homologous
Structures-structures that
have different mature forms in different
organisms, but develop from the same
embryonic tissue
Analogous Structures
 Analogous
Structures-structures that
have similar mature forms in different
organisms, but develop from different
embryonic tissue
Similarities in Early
Development
Evidence for Evolution
 Vestigial
organs-organs that serve
no useful function in an organism
 i.e.
appendix, miniature legs, arms
Summary of Darwin’s Theory

Individuals in nature differ from one another

Organisms in nature produce more offspring than
can survive, and many of those who do not survive
do not reproduce.

Because more organisms are produced than can
survive, each species must struggle for resources

Each organism is unique, each has advantages and
disadvantages in the struggle for existence
Summary (cont.)

Individuals best suited for the environment survive
and reproduce most successfully

Species change over time

Species alive today descended with modification
from species that lived in the past

All organisms on earth are united into a single
family tree of life by common descent
The Tree of Life
•
All living things share a common ancestor.
•
We can draw a Tree of Life to show how
every species is related.
•
Evolution is the process by which one
species gives rise to another and the Tree of
Life grows and branches
So HOW does it all happen?

There are a series of mechanisms that make
evolution happen in any living thing
Mechanism (1): All in the Genes
• The genetic make-up of
an organism is known as
its genotype.
• An organism’s genotype
and the environment in
which it lives determines
its total characteristic traits
i.e. its phenotype.
Genotype
Phenotype
commons.wikimedia.org/wiki/Image:DNA_double_helix_vertikal.PNG
Mechanism (2): DNA
• The double-helix
structure of DNA
was discovered
in 1953.
Watson and Crick and
their model of DNA
DNA
replication
www.chem.ucsb.edu/~kalju/chem110L/public/tutorial/images/WatsonCrick.jpg
en.wikipedia.org/wiki/DNA
• This showed how
genetic information
is transferred from
one cell to another
almost without error.
Mechanism (3): Mutation
Types of mutation
• However, occasional
mutations or copying errors
can and do occur when
DNA is replicated.
• Mutations may be caused
by radiation, viruses, or
carcinogens.
Mutant fruitfly
• Mutations are rare and often have
damaging effects. Consequently organisms
have special enzymes whose job it is to
repair faulty DNA.
upload.wikimedia.org/wikipedia/commons/7/79/Types-of-mutation.png
humansystemstherapeutics.com/bb.htm
Mechanism (4): Variation
• Nevertheless, some
mutations will persist and
increase genetic variation
within a population.
• Variants of a particular
gene are known as alleles.
For example, the one of
the genes for hair color
comprises brown/blonde
alleles.
majorityrights.com/index.php/weblog/comments/racial_variation_in_some_par
ts_of_the_skull_involved_in_chewing/
Mechanism (5): Natural Selection
Selection of dark gene
• Mutant alleles spread through a
population by sexual reproduction.
• If an allele exerts a harmful effect,
it will reduce the ability of the
individual to reproduce and the
allele will probably be removed
from the population.
• In contrast, mutants with favorable
effects are preferentially passed on
en.wikipedia.org/wiki/Image:Mutation_and_selection_diagram.svg
Mechanism (6): Peppered Moth
Haldane and the peppered moth


http://en.wikipedia.org/wiki/Image:Biston.betularia.7200.jpg
en.wikipedia.org/wiki/Image:Biston.betularia.f.carbonaria.7209.jpg
en.wikipedia.org/wiki/J._B._S._Haldane
• The Peppered Moth is an
example of Natural Selection
in action discovered by
Haldane
• During the Industrial
Revolution
the trees on which the moth
rested became soot-covered.
• This selected against the allele for pale
color in the population (which were
poorly camouflaged from predators)
and selected for the dark color allele.
Mechanism (7): Microevolution
• The dog is another example of how
selection can change the frequency
of alleles in a population.
• Dogs have been artificially selected
for certain characteristics for many
years, and different breeds have
different alleles.
Dogs are wolves
• All breeds of dog belong to the same
species, Canis lupus (the wolf) so this
is an example of Microevolution as no
new species has resulted.
www.puppy-training-solutions.com/image-files/dog-breed-information.jpg
Mechanism (8): Macroevolution
• However, if two populations of a
species become isolated from
one another for tens of thousands
of years, genetic difference may
become marked.
• If the two populations can no-longer
interbreed, new species are born.
This is called Macroevolution.
Galapagos finches
• Darwin’s Galapagos finches are
an example of this process in action.
www.ingala.gov.ec/galapagosislands/images/stories/ingala_images/galapagos_take_a_tour/small_pics/galapagos_map_2.jpg
Mechanism (9): Speciation Today?
• The mosquito was introduced to
the London Underground during
its construction around 1900.
London Underground Mosquito
en.wikipedia.org/wiki/Image:Gb-lu-Angel-southbound.jpg
en.wikipedia.org/wiki/Culex
• It became infamous in the War
for attacking people sheltering
from the Blitz.
• Studies indicate several genetic
differences from its above-ground
ancestors. Interbreeding between
populations is difficult suggesting
that speciation may be occurring.
Primordial Soup

Hypothesized that organic molecules could form in
the right conditions using electricity and inorganic
molecules

Once organic molecules existed, proteins could be
made

Proteins come from specific orders of DNA

Membranes protected the DNA and a cell formed
Cellular Evolution

Prokaryotes first: smaller, simpler cells that
can live in harsh environments

Photosynthesis became a process to make
food once oxygen was found in the
atmosphere from stromatolites
Endosymbiont

This theory is based on the idea that small,
prokaryotic cells were swallowed into larger cells
and became part of their host cell.

The smaller cells evolved into organelles

Chloroplasts and mitochondria have their own
DNA and protein synthesis process separate from
the rest of the cell in mitosis
PRIMATE EVOLUTION
Humans appeared late in Earth’s history.
Humans share a common ancestor with
other primates.

Primates are mammals with flexible hands and feet,
forward-looking eyes and enlarged brains.
Primates evolved into prosimians and
anthropoids.
– Prosimians are the oldest living primates.
– They are mostly small and nocturnal.
PRIMATE CHARACTERISTICS
First primates were arboreal – associated features that we’ve inherited.
Topic 14 – Human Evolution
Prosimians – Lorises and Lemurs
Topic 14 – Human Evolution
Prosimians: Tarsiers
10 cm
They are subdivided into the New World monkeys,
Old World monkeys, and hominoids.
– Homonoids are
divided into
hominids, great
apes, and lesser
apes.
– Hominids include
living and extinct
humans.
Bipedal means walking on two legs.
– foraging
– carrying infants and food
– using tools
• Walking upright has
important adaptive
advantages.



Most hominids are either the genus Australopithecus or
Homo.
Australopithecines were a successful genus.
The Homo genus first evolved 2.4 million years ago.



Homo sapiens fossils date to 200,000 years ago.
Human evolution is influenced by a tool-based culture.
There is a trend toward increased brain size in hominids.
Australopithecus
afarensis
Homo habilis
Homo
neanderthalensis
Homo sapiens
Topic 14 – Human Evolution
Primate Tree of Life
Our Closest Primate Relatives
Topic 14 – Human Evolution
Types of ‘Humans’
†Homo habilis (Handy Man)
†Homo rudolfensis (Rudolf Man)
†Homo ergaster (Working Man)
†Homo erectus (Upright Man)
†Homo floresiensis (Flores Man — discovered 2003)
†Homo antecessor (Predecessor Man)
†Homo heidelbergensis (Heidelberg Man)
†Homo neanderthalensis (Neanderthal Man)
†Homo rhodesiensis (Rhodesia Man)
†Homo cepranensis (Ceprano Man)
†Homo georgicus (Georgia Man)
†Homo sapiens idaltu (elderly wise man — discovered 1997)
Topic 14 – Human Evolution
Characteristics of Humans
-bipedal
-much less hair
-reduced sexual dimorphism
-larger brain
-shorter jaw, snout
-speech
-symbolic thought (not unique)
-complex tools
-habitat: variable
-diet: variable
Changes in Posture
Topic 14 – Human Evolution
How the shape of the skull changed
Opening in
skull reveals
upright posture
Topic 14 – Human Evolution
H. sapiens skull is very distinctive
Two theories:
1)
2)
Multiregional hypothesis
(multiple origins)
Replacement hypothesis
(single origin)
“negroid”
“mongoloid”
“caucasoid”
Homo erectus
Topic 14 – Human Evolution
Geographical Changes
Two theories:
1)
2)
Multiregional hypothesis
(multiple origins)
Replacement hypothesis
(single origin)
H. sapiens fossil record
H. sapiens (15 Ka): America
H. sapiens (40 Ka): Australia
H. sapiens (50 Ka): Asia, Europe
H. sapiens (195 Ka): E Africa
Europe: H. heidelbergensis
& H. neanderthalensis (400-40 Ka)
Homo erectus (1.6 Ma-200 Ka)
Topic 14 – Human Evolution
Modern Day Skull Shapes
“negroid”
“caucasoid”
Europe: H. heidelbergensis
& H. neanderthalensis (400-40 Ka)
“mongoloid”
Chapter 17
Organizing Life’s Diversity
Classification
Classification: The grouping of
objects or information based on
similarities
Taxononmy: The branch of biology
that groups and names organisms
based on studies of their different
characteristics.
Aristotle’s System
Greek Philosopher, 384 -322 B.C.


Developed the first widely accepted system.
Two groups

Plants

Divided into three groups
• Herbs, shrubs, trees

Animals, grouped them according to where they lived.


Land, in air, or in water.
Many centuries passed before a new system
was used.
Carolus Linnaeus’s System
Swedish Botanist, 1707-1778
 Linnaeus’s
system was based on physical and
structural similarities of organisms.
 This form of classification is the basis of the
modern classification system
Two names for a species
Linnaeus developed it

Binomial nomenclature, two word naming.
First word identifies the genus of the organism
 Genus; group of similar species
 Second word often describes a characteristic of the
organism.
• Example: Homo sapiens
 The Latin language is used to name an organism
 No longer used in conversation, so it doesn’t
change meaning.
 It is universal throughout the world.

BIOLOGICAL CLASSIFICATION
 Taxonomist:
identifies the underlying natural
relationships of organisms and use the information as a
basis for classification.


They compare the external and internal structure of an organism.
The organism’s geographical distribution and chemical makeup may help in
revealing the probable evolutionary relationships.
 Taxonomy
is a framework to find organisms that are
related

Ex. Are dinosaur’s more related to reptiles or birds?
 Taxonomy

is a useful tool
Poison control: figure if plant or animal are poisonous.
 Taxonomy
is good for the economy.
HOW LIVING THINGS ARE
CLASSIFIED
 ORGANISMS
ARE RANKED IN ARBITRARY TAXA
THAT RANGE FROM HAVING VERY BROAD
CHARACTERISTICS TO VERY SPECIFIC
CHARACTERISTICS.

Kingdom; very broad characteristics







Example: animal kingdom, butterfly and an elephant
Phylum
Class
Order
Family
Genus
Species: very specific


Example: sapiens
Genus species make up the scientific name.
Figure 17.5
Page 459
Section 17.2
The SIX KINGDOMS
How are evolutionary relationships
determined?





Structural similarities
Breeding behavior
Geographical distribution
Chromosome comparisons
Biochemistry
PHYLOGENETIC
CLASSIFICATION
Models
Phylogeny:
the evolutionary history of a
species
Phylogenetic classification uses the
evolutionary history of a species to reveal the
evolutionary relationships of species.

Example: cladistics, assume that groups of
organisms diverge and evolve from a common
ancestral group.
THE SIX KINGDOMS
Used to be two, the three, the five, now six
Prokaryotes: broken into two new
kingdoms







1. Archaebacteria
2. Eubacteria
Protists
Fungi
Plant
Animals
PROKARYOTES
Archaebacteria and Eubacteria
 Archaebacteria
Found in extreme environments such as
swamps, deep ocean hydrothermal vents etc..
 Only a few hundred species
 Eubacteria
 More than 10,000 different types
 Very strong bacteria
 Less complex than Archaebacteria

Protists
A very diverse group
A
protist is a eukaryote type cell
 Lacks complex organ system
 Lives in moist environments
 Some are unicellular some are multicellular
 Some are more plantlike some are more animal
like and some are fungi like.
FUNGI
 Heterotrophs
 Do
not move from place to place
 Either unicellular or multicellular
 More than 100,000 known species of fungi
Plants
Multicellular oxygen producers
 All
are multicellular with cell walls
 All photosynthesize, Autotrophs
 Plant cells usually contain chloroplast, roots cells
do not.
 Plant cells are organized into tissue,

Tissue is organized into organs that are organized into systems.
 More
than 500,000 known different plant species.
ANIMALS
Multicellular consumers
 Heterotrophs
 Nearly
all are able to move from place to place.
 Do not have cell walls
 Very organized
 Cells, tissue, organs, systems.