WA RM -UP

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WARM-UP

1. If the half-life of Carbon-14 is approximately
   5,700 years, how long will it take a sample to
   decay from 10g to 2.5g?
2. Which part of Earth is the oldest?
3. Which of these questions speaks to theory and
   which to evidence?

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EVOLUTION

• Evidence Theory

Natural Selection is the means by which evolution
is thought to occur! (Write this down!)
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Evidence Key Terms

1. Fossil record
2. Radioactive dating (half-life)
3. Relative dating
4. Endosymbiosis
5. Biogeography
6. Biochemistry

1. Embryology
2. Comparative morphology
3. Homologous structure
4. Analogous structure
5. Vestigial structure

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A long time ago in a galaxy far away

• 5 billion years ago the solar system was a gas
  cloud.
• The sun formed a few million years later.
• The remaining gases, debris, and dust orbited the
  sun due to gravity.
• Consequently, particles collided and accreted
  into planets.

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Planets constantly changed

• Bombardment of debris and particles increased the
  mass of planets and the thermal energy.
• This thermal energy would have melted Earths
  surface.
• Over time, while Earth cooled (thermal energy
  escapes back into space), particulates and gases
  precipitated to the surface.

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How did life begin?

• Toxic, inorganic compounds in Earths early
  atmosphere (ammonia, cyanide, methane, sulfur
  oxides) inhibited life
• Tiny bubbles of organic mixtures could have
  evolved from the inorganic soup that made up
  Earths early atmosphere and surface under
  certain conditions.
• The process was replicated by Harold Urey
  and Stanley Miller
• These tiny bubbles looked and acted
  like cells although not alive!

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What were the first cells?

• Archaebacteria they are the only organism that
  could survive Earths harsh conditions
  (chemosynthesis).
• Next, Cyanobacteria (photosynthesis) evolved
  which enriched Earths atmosphere with oxygen.
• Then, eukaryotes evolved from simple prokaryotes
  that engulfed other prokaryotes (endosymbiosis).
• Finally, single-celled eukaryotes evolved into
  multicellular eukaryotes.

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Summary

• Earth is really old (4.6 billion years)!
• Early conditions were too harsh, anaerobic for
  life!
• Hearty bacteria are the most ancient known
  organism
• Eukaryotes evolved from bacteria

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evolution

• Works that contributed to the theory of

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Scientists weve studied
Lynn Margulis Endosymbiont Theory proposed
that mitochondria and chloroplasts used to be
prokaryotes that were in a symbiotic relationship
with a host. Francesco Redi disproved
Spontaneous Generation. Life comes from existing
life. Harold Urey worked with Stanley Miller.
Proved that organic molecules necessary for life
could be made in the early atmosphere of Earth
and the oceans (Oparins Hypothesis)
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James Hutton

• Interior of the Earth is hot heat drives the
  creation of new rock
• Land is eroded by air and water and deposited as
  layers

• Geological changes happen by means of gradual
  processes still happening in present day
• Earth needed to be ancient in order to allow time
  for the changes

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Thomas Malthus

• If unchecked populations grow exponentially
• Populations overstretch their resource limitations

• Struggle for existence provides the catalyst by
  which natural selection produces the "survival of
  the fittest",

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Charles Lyell

• The earth was shaped entirely by slow-moving
  forces acting over a very long period of time

• Recent rock layers could be categorized according
  to the number and proportion of marine shells
  encased within

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Jean Baptiste Lamarck

• A transforming force drove organisms up a ladder
  of complexity

• A second environmental force adapted them to
  local environments through "use and disuse" of
  characteristics

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• That would mean that if you worked out every day
  or studied biology every day, your fitness would
  be inherited by your babies meaning they
  inherently benefit from your hard work.
• Given our current knowledge of genes and
  inheritance this is not possible!

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So how do we explain new life forms appearing to
be modifications of fossil forms found in the
same place? Simplea natural modification process
was at work evolution.
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OK, so evolution is the process by which modern
organisms have descended from ancient ancestors.
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Andevolution is responsible for both the
remarkable similarities we see across all life
and the amazing diversity of that life but how
does it work?
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Charles Darwins take
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Charles Darwin (1809-1882)

• Took a job as a naturalist on the English ship,
  HMS Beagle, which sailed to S. America on a
  scientific trek.
• The biological specimens (animals) that he
  studied in the Galapagos Islands were
  specifically interesting to Darwin. These animals
  were distinctly their own species but were
  similar to species found elsewhere, which led
  Darwin to believe that organisms could change
  over time.
• He spent the next 22 years studying how animals
  could change over time.
• Darwin used an idea proposed by Thomas Malthus
  about human population growth to explain that
  through competition and limited resources, only
  some are able to survive to reproduce.

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Charles Darwins take
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Darwins finches

• Populations of finches in one area had a
  different beak shape and size than finches in
  another area or on another island. The question
  was why?

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Who has the better beak?
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Darwins finches

• Species evolved different beaks in order to
  utilize the specific food limited to the area the
  finch inhabited.

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Darwins Finches

• Based on his observations Charles Darwin thought
  the finches shared a common ancestor but their
  beak modification occurred by natural selection.

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Darwin, cont.

• Darwin experimented with breeding pigeons and
  discovered that different populations had
  different traits and that these traits are passed
  down to future generations.
• Breeding organisms with specific traits in order
  to produce offspring with identical traits is
  known as artificial selection.
• Darwin believed there was a force in nature that
  was similar to this.
• Natural Selection is the mechanism by which
  traits within a population change over time.

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In summary, Charles Darwin thought

• Descent With Modification

• Newer forms are actually the adapted descendants
  of older species. Finches shared a common
  ancestor but their beak occurred by

• Modification by Natural Selection

• Environment limits population growth (natures
  way of selecting)

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Darwin, cont.

• Though another naturalist, Alfred Russell
  Wallace, was working on similar work and added to
  Darwins work, Charles Darwin was the first to
  publish his book on the subject, On the Origin of
  Species by Natural Selection in 1859.
• Difficulties
• Because evolution is a slow and gradual process,
  it is difficult for humans to directly observe.
• Due to the immensity of time in relation to the
  rather short span of human life, it is hard to
  comprehend the time it involves.
• It can sometimes be considered contradictory to
  personal religious beliefs.

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Principles of Natural Selection

• Organisms produce more offspring than can survive
  (overproduction)
• Genes are inherited from parents (Heritability)
• Variation of traits exists within populations
• Individuals with variations suitable to the
  habitat survive reproduce (reproductive
  advantage)

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Theories of Evolution

• Lamarck (50 yrs before Darwin)

• Darwin

• Similar species descended from a common ancestor
• New life-forms appeared to be modified fossil
  forms, or forms with acquired traits
• Species were modified through continued use or
  disuse of traits
• Traits were passed on to offspring

• Similar species descended from a common ancestor
• New life-forms appeared to be modified fossil
  forms, or forms with adaptations
• Species were modified by natural selection
  adaptations help organisms reproductive fitness

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Conclusion

• Individuals with more favorable traits tend to
  leave more offspring and will become more common
  in the population from one generation to the next.

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Natural Selection

• Results in adaptation a population becomes
  better suited to its environment
• Adaptation can also refer to a derived trait, one
  that has come about by natural selection.

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Adaptations Evidence for Evolution

• Adaptation
• Definition any variation that aids an organisms
  chance of survival in its environment.
• Evolution explains how they develop in the 1st
  place.
• Develop over many generations.
• Mimicry
• Definition structural adaptation that enables
  one species to resemble another.
• ex yellow jacket wasps and syrphid flies
• Camouflage
• Definition adaptation that allows an organism to
  blend into its surroundings
• ex leaf frog

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Adaptation

• Camouflage

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Adaptation

• Mimicry

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Modeling predatory selection

• Click on the picture below to try your hand at a
  peppered moth simulation
• Choose the circle with the bird pictured

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Artificial Selection

• Man selects for desired traits
• Traits in pet breeds are selected by man

Dalmatian lots of spots!!!
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Artificial Selection

• Man selects for desired traits
• Traits in livestock are selected by man

Angus Brahman cattle Brangus cattle (heat
tolerant, quick to cull)
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Artificial Selection

• Man selects for desired traits
• Traits in crops are selected by man

Crops cultivated from wild mustard
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Biological Resistance

• What happens to the herbicide-sensitive weeds?

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Biological Resistance

• When people take an antibiotic you hope it kills
  off all the bacteria that are making you sick, or
  at least kill off enough to let the body handle
  the rest. This does not always happen. Some of
  the bacteria will have a natural resistance to
  the drug. They survive the treatment. And because
  the bacteria without the natural resistance are
  now gone, the resistant ones have the opportunity
  to reproduce and fill the space the nonresistant
  left available. The bacteria with the trait to
  resist the drug spread quickly to fill the void
  and, in the usual ways of contamination, will
  spread to other people.

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Biological Resistance contd

• The shorter the lifespan of an organism, the
  faster adaptations can occur. (ex bacteria)

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Other Evidence for Evolution

• Fossils
• Provide a record of early life and evolutionary
  history.
• Like a puzzle, even with missing pieces we can
  envision the overall picture.
• Anatomy
• Homologous Structures
• Structural features with a common evolutionary
  origin.
• the ex forelimbs of whales and crocodiles
• Shows evidence of a common ancestor, which shared
  the same characteristic.
• Always similar in arrangement and sometimes in
  function.
• Analogous Structures
• Structural features that have evolved
  independently of each other.
• ex wings of a butterfly and wings of a bat
• Have similar function but not arrangement.

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Other Evidence, cont.

• Vestigial Structures
• Structural features that have no function in the
  present-day organism but that was useful to its
  evolutionary ancestors.
• ex eyes of moles / cave fish or pelvic girdles
  in pythons
• Embryology
• Similarities in early embryos suggest evolution
  from a common ancestor
• Biochemistry
• The sequences of RNA or DNA can be compared
  between organisms.
• The closer in sequence a gene is, the more
  closely related the organisms are to each other.

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Biochemical Similarities

• Molecular Clock Hypothesis relates the divergence
  time of two species to the number of molecular
  differences measured between the species' DNA
  sequences or proteins.
• The more molecular similarities the shorter the
  divergence time between species.

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Homology vs. Analogy
Jellyfish Fossils
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Vestigial Structures
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Embryology
Biochemistry
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Fossil Evidence

• The fossil record provides us a history of Earth
  and the evolution of biodiversity in terms of
  geologic time.
• Geologic time scale refers to the amount of time
  it takes Earths elements to cycle through their
  various forms a VERY LONG TIME!

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Geologic Time Scale
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Fossil Evidence

• To help determine an organisms place in
  evolutionary history, scientists use radioactive
  dating.
• Radioactive dating calculates the age of an
  artifact based on the time it takes a radioactive
  isotope to reach its half-life (time needed to
  reduce by ½).
• Now, you do the math

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Radioactive Dating

• If the half-life of Carbon-14 is approximately
  5,700 years, how long will it take a sample to
  decay from 10g to 2.5g?
• 11,400 years

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Radioactive Dating

• Radium decays exponentially with time, it has a
  half life of 25 years. If a chemist leaves 0.500
  kg of Radium on a shelf how much will be left in
  100 years time?
• 0.03125 kg

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Fossil Evidence

• Relative dating dates artifacts by dating rock
  layers in which they are trapped
• Law of Superposition rock and sediment deposit
  on Earth in layers older layers are buried below
  newer layers.

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Fossil Evidence

• Because more than half of all organic life was
  soft-bodied there are large gaps in the fossil
  record
• Sometimes there is very little evidence to link
  one organism with another through a common
  ancestor

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Evidence of Evolution

• BIOGEOGRAPHY

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Biogeography

• Distribution of biodiversity over space
• The patterns of species distribution that occur
  through a combination of factors such as
  speciation, extinction, and geographical
  isolation and available energy supply

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Biogeography

• Africa has short-tailed monkeys. S America has
  long-tailed monkeys.
• Australia has the only living representatives of
  primitive egg-laying mammals. On the other hand,
  Australia has very few placental mammals.

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Evidence of Evolution

• EMBRYOLOGICAL SIMILARITIES

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Embryological Similarities

• Growth development patterns
• Many organisms are very similar in appearance and
  have common features as embryos but vary
  significantly as adults.

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In frogs, the digits grow outwards from buds as
cells divide
In humans, programmed cell death (apoptosis)
divides the ridge into five regions that then
develop into fingers and toes
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Can you confirm your results from before using
the embryology diagrams provided?
Compare each of the 6 embryological stages
pictured among the organisms describe how this
new evidence supports, rejects, or refines your
previous hypothesis. Write a new hypothesis if
needed.
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Evidence of Evolution

• BIOCHEMICAL SIMILARITIES

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Biochemical Similarities

• All livings things have DNA
• DNA is the same language in all organisms even
  though they may be very different

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Biochemical Similarities

• Most often used is the biochemical comparison of
  proteins.
• The order of amino acids in a protein determines
  its structure and function. It also determines
  the sequence of nucleotides in DNA (genes).
• Cytochrome-C (cellular respiration) and
  Hemoglobin (blood) are two commonly used
  proteins.

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Biochemical Similarities

• Researchers believe that the greater the
  similarity in the amino-acid sequences of two
  organisms, the more closely related they are in
  an evolutionary sense.
• Conversely, the greater the time that organisms
  have been diverging from a common ancestor, the
  greater the differences in the AA sequence.

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Evidence of Evolution

• COMPARATIVE MORPHOLOGY

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Comparative Morphology

• Comparing similar structures in different
  organisms can help explain relationships among
  different species.

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Comparative Morphology

• Homologous structures
• Similar body parts found in different species
• Similar in development pattern within organism
• May be used for different skills though!

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Homologous -
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Comparative Morphology

• Analogous structures
• Serve same purpose in different species but they
  are not similar
• Its likely they evolved as a result of similar
  selective pressures
• Examples Wings of bats, birds and insects
  jointed legs of insects and vertebrates tail fin
  of fish, whale, lobster eye of vertebrate
  molluscs

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Comparative Morphology

• Vestigial structures
• Similar body parts found in different species
• Usually reduced in size because the structure is
  no longer used for its given purpose

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Morphology Homologous structures evolved from common ancestor Vestigial structures evolved from common ancestor but are no longer serve any purpose Analogous structures evolved from similar selective pressures
Development All chordates (including humans) have pharyngeal gill slits at some stage of their development (embryology).
DNA Humans and chimpanzees share 97 of the same sequence of amino acids and types of proteins
Behavior A fossil of a dinosaur sitting on a nest of eggs (brooding behavior) provides evidence that birds evolved from dinosaurs
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Summarizing What Weve Studied
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Mechanisms of Evolution

• Prezygotic Isolating Mechanisms
• Postzygotic Isolating Mechanisms
• Allopatric Speciation
• Sympatric Speciation

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Prezygotic Isolating Mechanism

• Occur before fertilizaton
• In the form of geographic, ecological, or
  behavioral differences
• Ex differences by species in mating behavior
  (songs/dances), mating times
• Ex Different species of fireflies mate at
  different times of night

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Postzygotic Isolating Mechanism

• Occur after fertilization occurs
• Ensures any hybrid organism remains infertile and
  cannot reproduce.
• Examples Ligers (Lions and Tigers can mate, but
  remain separate species because a Liger is
  sterile) Zedonks (Zebras and Donkeys) Mules
  (Horse and Donkey)

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Allopatric Speciation

• Physical barrier divides one population into two
  or more populations.
• With enough time, the subpopulations become their
  own species and are no longer able to breed with
  the parent population
• Mountains, wide rivers, lava flows, canyons
  physical barriers

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Sympatric Speciation

• No physical barrier
• Ancestor species and new species live side by
  side during speciation process.
• Can be caused by change in food source or genetic
  mutations.
• Found commonly in plants

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Patterns of Evolution

• Coevolution
• Divergent evolution
• Adaptive Radiation
• Convergent evolution

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Patterns of Evolution

• Coevolution
• One species adapts in response to anothers
  adaptation
• Symbiotic in nature. May be mutualistic
  (beneficial) to both or an arms race.

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If a species of flower adapts larger petals. The
pollinator species, who relies on the flower for
food, must also adapt a longer beak in order to
reach the nectar.
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Patterns of Evolution

• Divergent evolution
• As species adapt to different environments they
  become more different which can lead to the
  formation of new species (speciation)
• Homologous structures result

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The horses evolved from a common ancestor but the
modern horse is better adapted for speed and diet
while the others have gone extinct.
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Patterns of Evolution

• Adaptive Radiation
• A type of divergent evolution that happens in a
  very quick amount of time evolutionarily speaking
• Occurs in response to the creation of new habitat
  or other major ecological event.
• Usually follows large scale extinctions
• Ex- Mammal diversification after mass extinction
  of dinosaurs

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Patterns of Evolution

• Convergent evolution
• Different species become more alike because they
  adapt to similar environments
• Analogous structures result.

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These aquatic organisms benefit from streamlined
bodies and fins, but they are not related by a
common ancestor. They have analogous structures.
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evolution

• Rates of

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Slow Rate of Change Gradualism

• Species adapt to new challenges over the course
  of their history, gradually becoming new species
• Species evolve at a slow, stable rate

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Rapid Rate of Change Punctuated Equilibrium

• Species change little over time
• Then, new species arise abruptly and are quite
  different
• i.e. Rate of speciation is a pattern of long
  stable periods interrupted (punctuated) by short
  periods of rapid change

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