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Evolution
Why not invoke the supernatural
(god or gods) to explain how we
got here?
• The task of science is to make use of nature’s
redundancy to describe the world simply.
• We can use only empirical data.
• Everything else is outside the realm of
science.
• We can’t use the methods of science to
confirm or reject the supernatural. (Science is
falsifiable; the supernatural is not.)
The National Association of Biology Teachers affirms that
teaching biology must be in a standards-based instructional
framework, upholding scientific integrity and the right to
teach accurate and current science without penalty of
political or religious influences on content. Experimentation,
logical analysis, and evidence-based revision, based on
detectable and measurable data, are procedures that clearly
differentiate and separate science from other ways of
knowing. Explanations or ways of knowing that invoke
metaphysical, non-naturalistic or supernatural events are
outside the scope of science and not part of a valid science
curriculum.
Submitted by the NABT Board of Directors April 8, 2008.
Theories of Evolution
• Darwin Wasn’t the
First:
– Heraclitus (543 –
477 BC)
“Evolution might
involve conflict and
a struggle for
survival.”
– LeMark: Inheritance
of Aquired
Characteristics
Theories of Evolution
• Hutton:
"...if an organised body is not in the situation and
circumstances best adapted to its sustenance and
propagation, then, in conceiving an indefinite variety
among the individuals of that species, we must be
assured, that, on the one hand, those which depart
most from the best adapted constitution, will be the
most liable to perish, while, on the other hand, those
organised bodies, which most approach to the best
constitution for the present circumstances, will be best
adapted to continue, in preserving themselves and
multiplying the individuals of their race."
Darwin
• Was different because he came up with a
MECHANISM that was TESTABLE:
The theory of evolution BY MEANS OF
NATURAL SELECTION
• Unlike many theories, his has not yet been
disproven. Amazing!
Early Earth
4.6 billion years old
Originally chaotic:
Volcanoes
• Produced gases
– N2, CO2, H2O, CO, CH4
– No O2; O in CO2, H2O, CO, CH4
» Know because rocks aren’t oxidized
• Extreme temperature variations
Lightening & UV Light
• Energy sources
How did the first organic
chemicals form?
• Oparin and Haldane hypothesized that
organic chemicals were made from the
gases of the early atmosphere and the
energy from lightening, UV light, and
radioactivity from the Earth’s core.
• These organic molecules accumulated in the
ocean creating an “organic soup” or
“primordial soup.”
Miller - Urey Experiment
Stanley Miller
Results of more recent, refined
Miller – Urey experiments
• 13 of 20 amino acids
• All bases of DNA and RNA
• Ribose
ALSO: found amino acids in
meteorites and
formaldehyde in tail of
Haley’s comet.
Life may have originated in
undersea vents
Biological Evolution
• Organic compounds had to come together to
form complex molecules.
– Clay could have attracted, held, and catalyzed
the reactions between them.
• Molecules have to self-replicate
– Some RNA can, AND they work as enzymes
• May have been original molecule of life.
Biological Evolution, cont’
• Membranes have to
form:
– Put amino acids and fat
in water, fat will
surround amino acids
in spheres similar to
cells.
• Split when get too big.
• Are selectively
permeable
Oldest Fossils
• Are of
microorganisms
• 3.485 billion
years old
• Found in
stromatolites
(mats of
bacteria)
Earliest Life
• Bacteria (prokaryotes)
– Heterotrophs
• Didn’t have the machinery to photosynthesize
• Absorbed organic nutrients from the primordial soup
– Probably a bag of RNA and that’s its
• Similar to today’s prokaryotes
Earliest Eukaryotes
• Developed by endosymbiosis:
– Theory by Lynn Margulis
– Large bacteria incorporated smaller, energy
producing bacteria
– Mutualistic, symbiotic relationship formed
eukaryotes from prokaryotes
• Large bacteria get nutrients
• Small bacteria get protection
Earliest Eukaryotes
Evidence for endosymbiosis:
• Mitochondria and Chloroplasts have
– Own DNA – like today’s bacteria
– Own ribosomes – like today’s bacteria
– Double membranes (outer may have been from
vacuoles that engulfed the bacteria)
Biodiversity Increased With the
Accumulation of Oxygen
Presently Earth has about 3 million different
kinds of organisms.
For variation you need sexual reproduction.
For sexual reproduction you need a lot of
energy.
To get a lot of energy (ATP) you need aerobic
respiration.
Biodiversity Increased With the
Accumulation of Oxygen
For aerobic respiration you need oxygen.
For oxygen you need photosynthesis.
For photosynthesis you need plants.
Variation did not come about until plants had
produced significant quantities of oxygen so
that aerobic respiration could take place.
Biodiversity and Oxygen
Number of different
kinds of organisms
Level of Oxygen Gas (O2)
4.6 billion
600 million ybp
SO: # of critters = sex = energy = O2 = photosynthesis
Empirical Evidence of Evolution
Fossil Evidence
• Study of fossils = paleontology
• Record is incomplete
– Most organisms decay
– Not all found
• NOTE: Older fossils found in deeper rock
– Not many people who hunt for them
Empirical Evidence of Evolution
Fossil Evidence
• Best finds:
Intermediate forms
(species to species)
– E.g., Archaeopteryx
& China fossils
• Feathers and wings of
birds, but teeth and
tails of reptiles.
Empirical Evidence of Evolution
Homologous Structures
Empirical Evidence of Evolution
Embryology
Empirical Evidence of Evolution
Genetic Information
Origin of Species
• Individuals do not evolve, populations do.
• Evolution
– change in a population through time
– Source of changes in genes
•
•
•
•
Mutations
Recombination at fertilization
Crossing over
Independent assortment
Origin of Species
– Outside Influences led to study of Epigenetics
•
•
•
•
Chemicals in the environment
Diet
Family History
????
Origin of Species
• Microevolution
– Change in gene frequency within an individual
population.
• Studies can help us tell what is going on in the
environment.
• Have to look at the gene pool
Hardy-Weinberg Law
(useful for studying large, sexually
reproducing populations)
A population will NOT change IF
1. There is no mutation
2. Mating is completely random
3. There is no migration in or out
4. Natural selection does not occur (one
individual is not favored over another)
Hardy-Weinberg Law
And How often does this happen?
A population will NOT change IF
1. There is no mutation
2. Mating is completely random
3. There is no migration in or out
4. Natural selection does not occur (one individual is not
favored over another)
NEVER – all populations evolve because
eventually the environment changes
http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/l
ife4e_15-6-OSU.swf
The Hardy Weinberg Equilibrium
F = “The frequency of”
So:
FA x FA + 2(FA X Fa) + Fa X Fa
= FA2 + 2 (FAFa) + Fa2 = 100%
Microevolution Example
Natural Selection of the Peppered Moth
Microevolution Example
Kinds of Selection
Stabilizing
Directional
Disruptive
Microevolution Example
Genetic Drift in Beetles: Occurs in small populations
because the chances of coming up with the
expected results is low compared to a large
population.
Microevolution Example
Founder Effect
Migrate out and
found a new
population with
different gene
frequency.
Microevolution Example
Bottleneck: number of organisms is drastically
reduced for a few generation and the ones that
survive have a different gene frequency.
Origin of Species
• Macroevolution
– Change in species
– Source of change in species = MUTATIONS
– Inherited variations give some individuals an
improved chance to survive and reproduce as the
environment changes.
• NOTE: ENVIRONMENT = LIVING THINGS TOO!
– Viruses and Bacteria
– Competitors
Origin of Species
• Organisms do not intentionally change.
They cannot “will” a mutation because they
“need” it. Those with mutations that help
them survive do. Those without, die.
Origin of Species
• For new species to evolve
– Two populations become so different in their
genetic makeup that they can no longer
interbreed.
– Most common mechanism that separates
populations: geographic isolation.
Geographic Isolation
Prezygotic Isolation
Other Forms of Isolation
Gamete Isolation –
sperm not
chemically
attracted to egg or
not gain entry to
egg
Prezygotic Isolation
Other Forms of Isolation
Seasonal
Isolation –
Trees may
give off
pollen at
different
times of
year
Prezygotic Isolation
Other Forms of Isolation
Zygote
doesn’t
develop
normally,
or produces
a sterile
offspring.
Postzygotic Isolation
Back to Geographic Isolation
New environments with few competitors
allow populations to easily separate and
go their own ways. Speciation will result
– Called adaptive radiation
Evolution - Rate
• Darwin:
– gradualism
• Niles Eldridge and Stephan J. Gould:
– Punctuated Equilibrium
• Fossil evidence shows long periods of stasis
followed by rapid change (an asteroid falls on your
head)
Gradualism
Punctuated
Equilibrium
Extinctions - Many
So What Do We Have
Today?
3,000,000 different types
of organisms.
“Types” means “species”
Species Concept
Two organisms are of the same species IF they
• Breed naturally
• Produce fertile offspring
“Species” is a man-made
term to help us organize
our thinking
Classification of Organisms
= Taxonomy
Now based on evolutionary
relationships (DNA) rather
than just physical
characteristics.
Physical characteristics are
important still
– About the only thing we
can see in fossils!
Classification System
Kingdom, Phylum (Division for plants), Class,
Order, Family, Genus, Species
Why not common names?
Which one of these is a gopher?
Florida
Washington
Classification System
Binomial nomenclature = Two-name naming
system
• Invented by Carolus Linnaeus
– Uses Latin (dead language doesn’t change)
Classification System
• Species name = genus + specific epithet
– E.g.,
• Homo sapiens (humans)
• Amphiprion percula
(clown fish)
Classifying Organisms
• Cladistics - based on evolutionary
relationships and homologous
structures
– Compare shared derived characteristics
Classifying Organisms
• Elves, Gnomes, Leprechauns, and
Fairies are thought to form an
evolutionary group of little people with
magic powers. However, the exact
relationships are unknown. Infer the
phylogenetic pattern based on the
following information.
Classifying Organisms
•
•
•
•
Pointy ears evolved from ears that
were not pointy.
Inhabiting woods is more primitive
than inhabiting other places
Ability to find hidden treasure
evolved from the lack of such ability
Ability to fly is primitive
Classifying Organisms
•
•
•
•
Elves: pointy ears; haunt woods;
can't find treasure; can't fly
Fairies:ears not pointy: live in
woods; can't find treasure; can fly
Gnomes: ears not pointy; live in
mines and quarries; find treasure;
can't fly
Leprechauns:ears not pointy; live in
woods; find treasure; can't fly
Classifying Organisms
Pointy
Ears
Elves
Gnomes
Leprechauns
Fairies
NOT
woods
Find
NOT fly
Treasure
X
X
X
X
X
X
X
Classifying Organisms
Elves
Leprechauns
Not live in
woods
Pointy Ears
Find Treasure
Fairies
Gnomes
Not Fly
Evolution
Nothing in Biology Makes Sense
Except in the Light of Evolution
Theodosius Dobzhansky (1900-1975)