Essential Question:

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Essential Question What are some theories
about the origin of life on earth?
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EVOLUTION

• The process by which modern organisms descend
  from ancient organisms

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Conditions on Early Earth

• 4.5 billion years ago
• Violent storms 100 years of rain
• Primitive atmosphere
• 1000s of active volcanoes giving off toxic
  gasses H2, N2, H2O, CO2
• Extremely hot temperatures
• 1000 mile-an-hour winds
• (no O2 until 2.3 by later)

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Later, Alexander Oparin hypothesized that the
gases in the primitive atmosphere lead to the
formations of organic molecules and finally
living things.
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Then, Miller and Urey tested Oparins experiment
found that life could have arisen from simpler
compounds present on a primitive Earth, giving
rise to Microspheres
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Formation of Microspheres

• Large organic molecules form tiny bubbles called
  proteinoid microspheres.
• Microspheres are not cells, but they have
  selectively permeable membranes and can store and
  release energy suggesting that microspheres may
  have given rise to cells

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Introduction of Oxygen

• The first life-forms evolved without oxygen
• About 2.2 billion years ago, photosynthetic
  bacteria began to pump oxygen into the oceans.
• Next, oxygen gas accumulated in the atmosphere.
• The rise of oxygen in the atmosphere drove some
  life forms to extinction, while other life forms
  evolved new, more efficient metabolic pathways
  that used oxygen for respiration.
• O2

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The Endosymbiotic Theory

• States that
• Eukaryotic cells formed from a symbiotic
  relationship with several different prokaryotes
• BECAUSE
• About 2 billion years ago, prokaryotic cells
  began evolving internal cell membranes.
• The result was the ancestor of all eukaryotic
  cells.

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Origin of Eukaryotic Cells

• Endosymbiotic Theory

Ancient Prokaryotes
Chloroplast
Plants and plantlike protists
Aerobic bacteria
Photosynthetic bacteria
Nuclear envelope evolving
Mitochondrion
Primitive Photosynthetic Eukaryote
Animals, fungi, and non-plantlike protists
Primitive Aerobic Eukaryote
Ancient Anaerobic Prokaryote
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Origin of Eukaryotic Cells
Aerobic bacteria
Ancient Prokaryotes
Nuclear envelope evolving
Ancient Anaerobic Prokaryote
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Origin of Eukaryotic Cells

• Prokaryotes that use oxygen to generate
  energy-rich molecules of ATP evolved into
  mitochondria.

Mitochondrion
Primitive Aerobic Eukaryote
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Origin of Eukaryotic Cells
Prokaryotes that carried out photosynthesis
evolved into chloroplasts.
Chloroplast
Photosynthetic bacteria
Primitive Photosynthetic Eukaryote
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Essential Question What evidence is there that
evolution has occurred?
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Evidence of Evolution
The remains of a once living thing
1. Fossils
Types
imprints
molds
petrified or frozen organisms
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(2) Radioactive dating

• Half-life -
• Time it takes for one half of a given quantity
  of a radioisotope to decay

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3. Comparative Anatomy
a. Homologous structures - parts of the body
that are similar in structure show evidence of
common origin
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b. Analogous structures parts of the body that
are similar in function but not structure does
not show common origin.
Birds wing and bees wing are analogous
structures
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c. Vestigial structure structures that no
longer function in the body may show
relationship with other organisms, indicate
common origin.
Examples appendix or a whales pelvis
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4. Comparative Embryology

• Early vertebrate embryos strongly resemble one
  another
• Same plan of development

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Two theories of Evolution
Jean Baptist Lamarck Theory of Acquired
Characteristics
Traits you develop you pass on---ACQUIRED TRAITS
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How would Lamarck explain the long neck on the
giraffe?
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(No Transcript)
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Would her children have longer necks?
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Charles Darwin Theory of Natural Selection
Survival of the Fittest
Fig. 17.5a, p. 274
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Galapagos Islands
SSS Beagle
EQUATOR
Galåpagos Islands
Isabela
Fig. 17.5b, p. 275
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Darwins Finches

• Each islands in the Galapagos had their own
  species of finch
• Each bird had a unique beak adapted for the food
  source of that island
• Because the birds were all similar
• Darwin realized they must have evolved from
  a common ancestor

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Fig. 17.7, p. 277
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KONA FINCH extinct
KAUAI AKIALAOA
AMAKIHI
LAYSAN FINCH
IIWI
AKIAPOLAAU
APAPANE
MAUI PARROTBILL
insect and nectar eaters
fruit and seed eaters
Fig. 19.12 p. 303
FOUNDER SPECIES
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1
A few individuals of a species on the mainland
reach isolated island 1. Speciation follows
genetic divergence in a new habitat.
3
2
4
Later in time, a few individuals of the new
species colonize nearby island 2. In this new
habitat, speciation follows genetic divergence.
1
2
Speciation may also follow colonization of
islands 3 and 4. And it may follow invasion of
island a by genetically different descendants of
the ancestral species.
1
3
2
4
Fig. 19.11 p. 303
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Theory of Natural Selection
1. Overpopulation as populations increase their
resources decrease
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Theory of Natural Selection
1. Overproduction leads to
2. Struggle for Existence competition occurs
food, shelter and living space.
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Theory of Natural Selection
1. Overproduction
2. Struggle for Existence
3. Genetic Differences give some organisms an
advantage
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Theory of Natural Selection
1. Overproduction
2. Struggle for Existence
3. Variations
4. Natural Selection those members best adapted
will survive longer reproduce offspring with
the advantageous traits.
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Theory of Natural Selection
1. Overproduction
2. Struggle for Existence
3. Variations
4. Natural selection
5. Speciation over time variations in an
isolated population will eventually produce a new
species
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How Natural Selection Works
Example The Peppered Moth
The peppered Moth, Biston beularis, lives in
England. There are two colors of this moth.
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Before the Industrial Revolution the bark of
trees were light colored because they were
covered with grey-green lichens. If you were a
bird which moth would you eat?
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After the Industrial Revolution the bark of the
trees were dark because the lichens were killed
by pollution. Which moth is visible now?
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Other Examples of Natural Selection

• Bacteria becoming resistant to antibiotics
• Insects becoming resistant to pesticides

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Patterns of Evolution

• Different patterns provide different paths to
  explain the degree of variation among organisms
• Convergent Divergent

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Convergent Evolution two different species that
did not come from a common ancestor but are very
similar in appearance and life style, Example
sharks and dolphins
Divergent Evolution two different species that
came from a common ancestor, Example horse and
donkey
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Natural selection can affect the distributions of
phenotypes in any of three ways

• 1. Directional Selection 
• individuals at one end of the curve have higher
  fitness than individuals in the middle or at the
  other end

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2. Stabilizing Selection 

• When individuals near the center of the curve
  have higher fitness than individuals at either
  end of the curve

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3. Disruptive Selection 

• When individuals at the upper and lower ends of
  the curve have higher fitness than individuals
  near the middle

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Genes Variation

• Genetic variation is studied in populations.
• A population is a group of individuals of the
  same species that interbreed.
• A gene pool consists of all genes, including all
  the different alleles, that are present in a
  population.

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• Relative Frequency is the number of times the
  allele occurs in a gene pool
• used to
• Predicts how often a particular allele will be
  expressed.
• In genetic terms, Evolution is any
  change in the relative frequency
  of alleles in a population

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Sources of Genetic Variation

• Mutations - any change in a sequence of DNA can
  produce an organism with better adaptive skills

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Genetic Drift A random change in allele
frequency

• Genetic drift may occur when a small group of
  individuals colonizes a new habitat.
• Individuals may carry alleles in different
  relative frequencies than did the larger
  population from which they came.
• The new population will be genetically different
  from the parent population
• When allele frequencies change due to migration
  of a small subgroup of a population it is known
  as the Founder Effect.

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Evolution Versus Genetic Equilibrium

• The Hardy-Weinberg Principle states that allele
  frequencies in a population will remain constant
  unless one or more factors cause those
  frequencies to change.
• When allele frequencies remain constant it is
  called
• Genetic Equilibrium

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Evolution Versus Genetic Equilibrium

• To maintain genetic equilibrium from generation
  to generation
• 1. Random mating must occur
• 2. Need very large population
• 3. No immigration or emigration
• 4. No mutations
• 5. No natural selection

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Speciation

• The formation of a new species
• A species is a group of
• organisms that breed with
• one another and produce
• fertile offspring.

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Fossils and Ancient Life

• Fossils and Ancient Life
• Paleontologists are scientists who collect and
  study fossils.
• A fossil is the remains of a once living thing
• Fossil record contains all available info about
  past life

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• The fossil record provides
• evidence about the history of life on Earth
• shows how different groups of organisms have
  changed over time.
• The fossil record is incomplete
• Over 99 of all species that have lived on Earth
  have become extinct.

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How Fossils Form

• Most fossils form in sedimentary rock when
  exposure to the elements breaks down existing
  rock into small particles of sand, silt, and clay.

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Aging Fossils

• Relative dating the age of a fossil is
  determined by comparing its placement with
  that of fossils in other layers of rock,
• as
• older fossils are at the bottom, more
  recent fossils are in the upper layers
• Radioactiv

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Aging Fossils

• Radioactive dating is the use of half-lives to
  determine the age of a sample.
• A half-life is the length of time required for
  half of the radioactive atoms in a sample to
  decay.
• By comparing the amounts of carbon-14 and
  carbon-12 in a fossil, researchers can determine
  when the organism lived.

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Interpreting Fossil Evidence
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Aging Fossils

• Index fossils provide a known base which is used
  to compare the relative ages of newly found
  fossils.