Download Evolution

Life’s Diversity
through Evolution
Science vs. Religion
What is science based on?
 Science is based on OBSERVABLE
evidence.
 What is religion based on?
 Religion is based on FAITH.

– By definition, faith is something that is not
observable.

Since they are 2 different “fields,” they are
not competing with each other
Religious Scientists?

My religion consists of a humble admiration of
the illimitable superior spirit who reveals himself
in the slight details we are able to perceive with
our frail and feeble mind.
– Albert Einstein (1879 - 1955)

Science without religion is lame, religion without
science is blind.
– Albert Einstein (1879 - 1955), "Science, Philosophy
and Religion: a Symposium", 1941

Not only does God play dice, but... he
sometimes throws them where they cannot be
seen.
– Stephen Hawking
Evolution is a Theory

Theory Defined: “scientific principle to
explain phenomena: a set of facts,
propositions, or principles analyzed in their
relation to one another and used,
especially in science, to explain
phenomena”
– MSN Encarta, http://encarta.msn.com/dictionary_/theory.html

Evolution is as much a theory as…
– Cell theory: biology
– Atomic theory: chemistry
– Plate tectonic theory: geology
A Final Quote
“Be opinionated,
just not
ignorant.”
Evolution

The theory that organisms on Earth have
changed over time is known as evolution.

Charles Darwin (1809-1882) is the man
who contributed more to our
understanding of evolution than any other
individual.
Charles Darwin
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English naturalist (scientist) 18091882
1831, Darwin took a job as a
naturalist on the HMS Beagle
– Went on a 5-year scientific
journey around the world
He collected many biological and
fossil specimens
– Combined with his previous and
subsequent observations
Published On the Origin of Species
by Natural Selection in 1859
– These ideas are a basic unifying
theme of biology today
– Without evolution, biology
doesn’t make as much sense
He realized that he had never seen many of
these organisms and the diversity of life on
Earth was enormous!
Darwin questioned
“Where did all of these different life forms come
from?”
EX: Darwin collected 68 species of beetles from
Brazil in just a few hours while on shore.
Darwin also
discovered many
fossils of organisms
that no longer existed
today. This lead to
other questions,
 “Where did all these
organisms go? And
why did they
disappear?”

Fitness
Darwin observed that many plants and
animals had parts and displayed behaviors
that helped them survive.
 Traits and behaviors that will help
organisms survive and reproduce in their
environment give those organisms greater
fitness (ability to survive and reproduce).
 Those organisms that are most fit will survive
and reproduce more often than those
organisms who are “less” fit.
 Became known as “survival of the fittest.”

– Darwin did not use that phrase, it came about later &
may lead to misconceptions…
Fitness
Darwin argued that increased fitness arises
from adaptations.
 Certain adaptations allow organisms to become
better suited to their environment, and thus better
able to survive and reproduce.
 Adaptations can be physical or behavioral


Does “struggle for existence” mean only the
biggest, strongest animals survive?
What types of characteristics
increases an organisms chance
of surviving?
Adaptations

Adaptation
– Evolution of a structure, behavior, or internal
process that enables an organism to respond to
environmental factors and live to produce
offspring
– Can also be the structure itself
Structural adaptations take a long time
 Physiological adaptations can happen faster

– Bacteria strains develop resistances to antibiotics
fairly quickly
Summary of Darwin’s Idea

There is variation between individuals.
Summary of Darwin’s Idea

Organisms tend to
have more offspring
than can possibly
survive, so there is
competition among
the offspring for a
limited amount of
resources
Summary of Darwin’s Idea
Organisms compete for limited resources
 There is a struggle for existence

Summary of Darwin’s Idea

Those organisms that
are best suited for
their environment
(most fit) will survive
and pass on their
genes.
Darwin’s Theory of Evolution
Darwin developed evolution by natural
selection
 Compared the process of natural selection
in nature vs. artificial selection used by
people. He used this comparison to
develop a hypothesis to explain how
evolution occurs.

Using artificial selection a breeder can produce plants
and animals that look very different from their
ancestors. Artificial selection uses the variation nature
provides.
How does horse racing relate to selective breeding?
Darwin’s Origin of Species
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He filled notebooks with
ideas about species
diversity & the process of
evolution.
His beliefs challenged the
fundamental ideas of that
time (species do not
change).
Darwin was very reluctant
to publish his book due to
his fear of what the public
would think.
Are their any scientific
topics today that are
controversial?
Origin of Species

1858, a naturalist name Alfred Wallace
sent him a letter describing evolution. He
had been working in Malaysia and come to
the same conclusions Darwin did.

Darwin had been working on his theory
and the evidence to support it for 20
years. Darwin published the Origin of
Species in 1859, 23 years after his trip.
Origin of Species

His book did two things:
1. Proposed a mechanism
for evolution (natural
selection)
2. Evidence showing it
had been taking place for
millions of years and
continues to take place
Descent with Modifications
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Over long periods of time,
natural selection will start
to produce organisms
with different structures
or organisms that occupy
different niches or
habitats. Because of this,
species today look
different from their
ancestors.
Selection

Artificial selection
– Breeding organisms with specific
traits in order to produce offspring
with identical traits

Natural selection
– A mechanism for change in
populations
– Occurs when organisms with
favorable traits survive, reproduce
and pass their traits on to the next
generation
 Organisms with these traits are
said to be more “fit”
 Organisms without these traits
are less likely to survive and
Darwin awards
Geological Evolution
– James Hutton (1788) proposed that
rain, wind, temperature, and natural
disasters shaped the valleys, mountains,
and rocks over extremely long periods
of time
– Charles Lyell (1830)contributed to this
by adding that current observations of
volcanic eruptions and other natural
disasters shows that Hutton was correct
in assuming the Earth was older than
originally predicted
Acceptance of Geological Evolution
Important to Darwin because it
established an OLD Earth
 Darwin’s theory of evolution required lots
of time
 Another important influence: Thomas
Malthus

– Observed that humans were being born at a
faster rate than they were dying
– War, famine, and disease control populations
– These observations provided enough curiosity
for Darwin to delve deep into his theory of
Natural Selection
humans evolve
First placental mammals
Flowering plants dominant
First birds
1st dinosaurs
First reptiles
First seed plants
First amphibians
First vertebrates
First invertebrates
eukaryotes
prokaryotes
Life evolves
Dating Techniques
Geologic Record
– Hypothetical library of all the known
geological processes on Earth
– Determined through inference and
dating methods
 Relative Dating (hee hee)
– Sediments are constantly being laid
down.
– Over time, many layers form
– If a fossil is in a layer below a different
fossil, it is older than that fossil
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Radiometric Dating
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Radiometric Dating
– Radioactive isotopes decay and form new
isotopes - the rate this happens is called
the isotope’s half life
– Ex: Potassium-40 decays to argon-40 and
has a half life of 1.3 billion years
 Half a sample will decay to argon-40 in
1.3 billion years
 So if there are equal amounts of
potassium-40 and argon-40 in an area,
the sample has been in place 1.3 billion
years
– Carbon 14 has a half life of only 7,000
years for more recent sample dating
Review
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4.
How does the geologic record help us?
What use is relative dating?
What is radiometric dating?
Why are different isotopes used in
radiometric dating?
Evidence for Evolution

Fossil Record
– A hypothetical “library”
of all the fossils
collected around the
world

Fossils show changes
throughout time
– 99 percent of all
animals are now
extinct
– Fossil record shows
ancestors with similar
characteristics
Embryology

Study of embryos and the
relationships that exist between
different species
Evidence for Evolution: Embryology
Many species share features in the young
embryos
– Ex: Mammals, reptiles, birds and fish all have
a tail and pharyngeal pouches (develop into
different respiratory systems)
Evidence For Evolution: Anatomy

Homologous Structures are structural features with
a common evolutionary origin
– Ex: whale forelimb, crocodile forelimb, bird wing, human
forelimb all look the same
– Can you think of other examples?

Analogous Structures are body parts or organisms
that do not have a common evolutionary origin but
are similar in function
– Bird, bat and butterfly wings
– Show how organisms adapt to different ways of life and
different conditions
Homologous Structures
Structure and Function between species is the same
Analogous Structures
Functions are the same between species;
structures are different
Evidence for Evolution

Vestigial Structures
are body structures
that no longer serve
their original purpose,
but was probably
useful to an ancestor
– Ex: human appendix,
pelvic bone in baleen
whale, “tail” in
humans, some
human’s ability to
wiggle their ears
Vestigial Structures
Evidence shows the organ was once used,
but not any longer
Evidence for Evolution
Biochemistry
 Nearly all organisms
share DNA, ATP, and
many enzymes
among their
biochemical molecules
 Organisms that share
more similar
enzymes, DNA
sequences, etc. are
more closely related

Review
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6.
How did Darwin come up with his ides for natural
selection?
Some snakes have vestigial legs. Why is this
considered evidence for evolution?
Explain how adaptations such as camouflage help
species survive.
How do homologous structures provide evidence for
evolution?
Why did birds and bats both get wings?
A parasite that lives in red blood cells causes the
disease called malaria. In recent years, new strains of
the parasite have appeared that are resistant to the
drugs used to treat the disease. Explain how this could
be an example of natural selection occurring.
Population Genetics
Populations evolve,
not individuals
 Natural selection acts
on a range of
phenotypes in a
population
 Evolution is often
defined as a change
in the frequency of an
allele in a population
over time

Population Genetics
All of the population’s
genes are in a theoretical
“gene pool”
 The percentage a specific
allele in the gene pool is
called the allelic frequency
 A population in which the
frequency of alleles
remains relatively the
same over generations is
in genetic equilibrium
 Any change in this genetic
equilibrium results in
evolution
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Hardy-Weinberg Principle
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How to Stop Evolution – must meet all five
requirements
Population is so large, chance alone cannot
change relative frequency (genetic drift doesn’t
occur)
Mutations do not occur
All genotypes have equal fitness (no natural
selection)
No organisms leave or enter a population
Mating occurs at random
Mutations
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Mutation provides the
raw material for
evolution to act upon
– Poor mutations are
selected against, good
mutations are selected
for
– Change the frequency
of alleles
– Examples:
Genetic Drift
Genetic drift is the
alteration of allelic
frequencies by chance
events
 Genetic drift can greatly
affect small populations
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– Ex: The Amish
community carries an
allele that results in short
arms and legs and extra
fingers and toes (1/14
vs. 1/1000)
Natural Selection
Still the most significant
factor that causes changes in
established gene pools
 Stabilizing Selection
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– Natural selection that favors
average individuals (on a
normal curve) in a population
– Reduces variation in a
population
– Ex: With spiders, larger ones
are found easier and eaten and
small spiders can’t find food as
easily
Natural Selection
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Directional Selection
– Natural selection favors one of
the extreme variations of a trait
– Can lead to rapid evolution
– Ex: The food supply in an area
is limited to hard nuts. Birds
with short, strong beaks will
survive

Disruptive Selection
– Natural selection favors
individuals with either extreme
of a trait’s variation
– Can lead to evolution of 2 new
species
– Ex: A shelled, marine organism
called a limpet has white, tan,
and dark shells. The white and
dark shells blend in on different
colored rocks. Tan gets eaten.
Species
A species is a group of
organisms that look
alike and can interbreed
to produce fertile
offspring in nature
 Speciation is the
evolution of new species

– Occurs when members of
similar populations no
longer interbreed to
produce fertile offspring
within their natural
environment
Causes of Speciation
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Physical barriers
– Volcanic eruptions,
sea-level changes,
new islands forming
These prevent
interbreeding
 Called geographic
isolation
 Over time, may have
to adapt to new types
of environments
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Causes of Speciation
Reproductive Isolation
 Two types
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– One occurs because of
geographical reasons
(migrate away)
– One occurs because of
behavioral reasons
 Some mate in fall,
some in spring
Polyploidy
Individual with a
multiple of a normal
set of chromosomes
 How does this
happen?
 New zygotes may not
develop the same
way as parents due to
different number of
chromosomes
 May result in
speciation
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Gradualism
James Hutton &
Charles Lyell
 Theory that processes
are moving at the
same speed today as
in the past
 Suggests that the
Earth is very old –
4.55 billion years
 Also suggests that
evolution occurs
constantly, but slowly

Punctuated Equilibrium
Remember first day of
class?
 Niles Eldredge and
Steven J. Gould
 Theory that speciation
occurs relatively, in rapid
bursts, with long periods
of genetic equilibrium
inbetween
 Might occur due to
drastic environmental
changes resulting in
quick adaptations
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Adaptive Radiation
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When an ancestral species
evolves into an array of
species to fit a number of
diverse habitats
Hawaiian Island
honeycreepers
– Similar in body size and shape,
but different sharply in color and
beak shape
– Adapted to occupy different
niches (what’s a niche)
Divergent Evolution

Adaptive radiation is a
type of divergent
evolution
– The pattern of evolution in
which species that once
were similar to an ancestral
species diverge, or become
increasingly distinct
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Galapagos Finches
– Similar changes for finches
that ended up on different
small islands
Convergent Evolution
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A pattern of evolution in
which distantly related
organisms evolve similar
traits
Occurs when different
organisms occupy similar
environments
– Adapt similar traits
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Example:
– Organ pipe cactus in N.
and S. American vs.
Euphorbiaceae in African
deserts both look very
similar
Review
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6.
Explain and illustrate why the evolution of resistance
to antibiotics in bacteria is an example of directional
natural selection.
How can geographic isolation change a population’s
gene pool?
Why is rapid evolutionary change more likely to occur
in small populations?
How do gradualism and punctuated equilibrium differ?
How are they similar?
Hummingbird moths are night-flying insects whose
behavior and appearance are similar to those of
hummingbirds. Explain how these two organisms
demonstrate convergent evolution.
What is divergent evolution? How does it compare to
adaptive radiation?
Quick Tour of Ch 17
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Classification – the grouping
of objects or information
based on similarities
Taxonomy – the branch of
biology that groups and
names organism based on
studies of their different
characteristics
Aristotle was the first on
record
– Classified organisms into
two groups: plants and
animals, each with
subgroups
Carolus Linnaeus
Developed taxonomic system
still used today
 Based on physical and structural
similarities of organisms
 Grouped life into 7 taxa (groups)
– What are they?
 Kingdom, phylum, class, order,
family, genus, species
 Five Kingdoms: animals, plants,
fungi, protists, monerans
 A six Kingdom system is
becoming more and more
common: monera split into
eubacteria and archaebacteria
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Binomial Nomenclature
All organisms have a two-word name
 Consists of their genus and their species

– Always italicized in type and underlined in
writing
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Genus is capitalized, species is lower case
– Homo sapiens (human)
– Passer domesticus (sparrow)
Classification Key
Sometimes called a
dichotomous key
 “Guide” for identifying
different species
based on observable
traits
 Useful for
distinguishing
between types of
organisms

Modern Classification
Generally based on
evolutionary
relationships vs.
physical characteristics
 Used structural
similarities, breeding
behavior, geographical
distribution,
chromosome
comparisons,
biochemistry to figure
out relationships

Phylogenetic Diagram

Monerans evolved first
(often broken up into
archaebacteria and
eubacteria)
– prokaryotes

Protists then evolved
– Single celled eukaryotes
– Three general kinds of
protists: fungus like,
animal like and plant like

Fungi, Plants and
Animals evolved from
the types of protists
Review
1.
2.
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4.
5.
Why does your book use the
classification system of six kingdoms
instead of five?
What two taxa does binomial
nomenclature consist of?
Why is classification hard to do?
What are the 7 Linnaean taxa?
How might you use taxonomic key to
figure out the name of an organism?