Descent With Modification: A Darwinian View of Life

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Descent With ModificationA Darwinian View of
Life

• chapter 22

Darwin Lamarck Lyell Linnaeus Hooke
Vestigial Organs Homologous structures Analogous Structures The Fossil Record Biogeography
Embryological Homologies Molecular Homologies Natural Selection Artificial Selection Inheritance of Acquired Characteristics
Galapagos Islands Uniformitarianism Gradualism Descent with Modification Taxonomy Evolutionary Adaptations
Match Distinguish Cite Evidence
Differentiate Critique Connect Create Who?
What? Where? When? Why? Which? How?
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What is evolution?

• Discuss _at_ your table.
• Provide examples of the evolutionary process.
• 1) WHO? Name the organism
• 2) WHAT? summarize the physical or behavioral
  traits that make it unique (adaptations)
• 3) WHY? correlate the cause-effect (trait ?
  ?advantage)
• 4) How? Hypothesize construct a scenario that
  would have led to the evolution of that trait.

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What is evolution?

• Organismic evolution means changes in
  populations, species, or groups of species.
• It occurs because
• 1. Populations vary by the frequency of
  heritable traits that appear from one generation
  to the next.
• 2. These traits are represented by alleles
  for genes that modify morphology
  (form/structure), physiology, or behavior.
• 3. There is a struggle for survival and most
  organisms perish. Only those that survive pass
  their genes on.

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Evolution is changes in allele frequencies over
time.

• Discuss what this statement means.

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Can individuals Evolve?

• NO. Individuals can BE different and can survive
  and pass those genes on or be killed and not.
• For an organism to change itself to suit its
  environment it would need to change the genes
  (DNA) inside every cell of its body.
• Most importantly, they would need to change the
  DNA in their gametes- so the change could be
  passed on to the next generation.
• Some individuals are better suited for their
  environment. They leave more offspring. Over
  generations, the genetic composition of a
  population reflects more of their beneficial
  genes.

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Two areas of evolutionary study

1. Microevolution describes the details of how
   populations of organisms change from generation
   to generation and how new species originate.
   (next chapters focus)
2. Macroevolution describes patterns of changes in
   groups of related species over broad periods of
   geologic time. The patterns determine phylogeny,
   the evolutionary relationships among species or
   groups of species. (fossil record)

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Evolution of insecticide resistance in insect
populations
Microevolution DDT resistance of insects
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Phylogenetic trees are diagrams that show
evolutionary relationships between groups of
extinct and extant organisms
Macroevolution Ex. Fossil Record
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The historical context of Darwins life and ideas.
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Historical Context of Evolutionary Theory

• Paradigm shift from organism are STATIC for to
  the idea that organisms can CHANGE FORM.
• Plato (427-347 B.C.) Two worlds real/ideal world
  that is eternal and world of imperfection we
  perceive through senses. Living things were
  created in their perfect, static form by the
  gods.
• Aristotle (384-322 B.C.) scale of nature all
  living forms could be arranged on. Each form
  assigned a rung, all rungs were taken.

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nonliving beings- lower plants-higher plants
sponges, jellyfish shellfish - insects --
crustacea cephalopoda -- ovipara - whales
ovoviviparous quadrupeds -- humankind. These are
the "steps of nature," or the "hierarchy of
nature LADDER OF LIFE
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Tree of Life / Bush of Life instead of a ladder
or hierarchy tips of branches
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Natural theology

• A philosophy dedicated to discovering the
  Creators plan by studying nature- the earth and
  its inhabitants.
• Adapations were evidence that the Creator had
  designed each and every species for a particular
  purpose.
• Classifying species was a major objective.

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Carolus Linnaeus (1707-1778)

• Specialized in taxonomy- naming and classifying
  the diverse forms of life.
• Developed binomial nomenclature- a two part
  naming system.
• Developed a system of grouping similar species
  into a hierarchy of increasingly general
  categories. (species- genus- family)
• He saw no evolutionary relationships in his
  groupings.

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Cuvier
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Georges Cuvier (1769-1832)

• largely developed paleontology- the study of
  fossils.
• Big idea species go extinct
• Observed a pattern of many strata separated by
  extinctions.
• Explanation catastrophism
• Each boundary between strata corresponded to a
  catastrophe (drought, flood,supervolcano)
  destroyed many of the local species.
• Area repopulated by immigration.

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Figure 22.4 Strata of sedimentary rock at the
Grand Canyon
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Figure 22.3 Formation of sedimentary rock and
deposition of fossils from different time periods
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Trilobite fossils- lived in the seas hundreds of
millions of years ago
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ex. 65mya the meteorite impact in the Gulf of
Mexico brought on the extinction of the
dinosaurs.
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Fathers of Modern GeologyHutton Lyell
HUTTON
LYELL
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• 1795 James Hutton, Scottish geologist
• Explained Earths geologic features by the
  theory of Gradualism Speciation occurs
  gradually, profound change is the cumulative
  product of slow but continuous processes.
• Charles Lyell (1797-1875) geologist
• incorporated gradualism into the theory of
• Uniformitarianism Geologic processes have not
  changed throughout Earths history (ie. forces
  that build and erode mountains occur at a steady
  rate) thus Earth is much older than previously
  believed.

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Figure 22.4 Strata of sedimentary rock at the
Grand Canyon
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Fossil Record Interpretation

• Gradualism
• Vs.
• Punctuated equilibrium

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Gradualism

• Argues that evolution occurs by the gradual
  accumulation of small changes.
• Individual speciation events or major changes in
  lineages occur over long periods of geologic
  time.
• Fossil evidence provides snapshots of the
  evolutionary process, revealing only major
  changes in groups of organisms.
• Intermediate stages of evolution not represented
  by fossils is due to the incompleteness of the
  fossil record.

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Punctuated Equilibrium

• Argues that evolutionary history consists of
  geologically long periods of stasis with little
  or no evolution,
• interrupted, or punctuated by geologically
  short periods of rapid evolution.
• The fossil record should consist of fossils
  mostly from the extended periods of stasis with
  few if any fossils from the short bursts of
  evolution.

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Phylogenetic trees are diagrams that show
evolutionary relationships between groups of
extinct and extant organisms
Macroevolution Ex. Fossil Record
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IMPORTANT CONCLUSIONS

• Earth must be very old much older than six
  thousand years (it is 4.5 billion years old)
• Very slow and subtle processes persisting over a
  long period of time can add up to substantial
  change.
• Slow but significant changes in environments
  caused slow but significant changes in species
  over geologic time.

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• By the end of the 18th century several
  naturalists, including Darwins grandfather
  Erasmus Darwin, suggested that life had evolved
  as environments changed.
• No one had suggested a mechanism.

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THEORY 2 parts

• Evolution, change in species over geologic time,
  does exist.
• Theory to explain WHY/HOW the mechanism causing
  this change.

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Lamarck
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The Inheritance of Acquired Characteristicsby
LAMARCK

• Jean Baptiste de Lamarck proposed the first
  explanation which was widely accepted for years.
• Three parts
• Use and disuse described how body parts of
  organisms can develop with increased usage, while
  unused parts weaken. Correct.
• Inheritance of acquired characteristics described
  how body features acquired during the lifetime of
  an organism (such as muscle bulk) could be passed
  on to offspring. Incorrect.
• Natural transformation of species described how
  organisms produced offspring with changes,
  transforming each generation into a slightly
  different form that is more complex. Species did
  not become extinct nor did they split and change
  into two or more species. Incorrect.

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The giraffe

• Short neck.
• Food scarce.
• Stretch neck.
• Eat.
• Longer neck.
• Offspring.
• Repeat.
• Inheritance of Acquired Characteristics or
  Lamarckism
• With a Partner Create a Lamarkian explanation
  for the evolution of one of your creatures.

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Descent with Modification via Natural Selection
by DARWIN

• Charles Darwin 1809-1882
• Med school dropout
• BA Natural Theology
• Captain Fitzroy- HMS Beagle
• Galapagos, islands of relatively recent volcanic
  origin, 900 km west of SA coast.
• Gathered mountains of evidence
• Waited 20 years to write and publish a
  groundbreaking book.

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Beaks adapted to specific foods available on
their home islands.
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• On the Origin of Species
• By Means of Natural Selection November 24, 1859
• Darwinss groundbreaking book explained what had
  once seemed a bewildering array
• of unrelated facts.
• He focused on
• Diversity of organisms
• Similarities differences
• Geographic distribution
• Adaptations to surrounding
• environments

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Main Ideas of Natural Selection

• Overproduction of offspring populations posses
  an enormous reproductive potential.
• ex. Darwin calculated that two elephants would
  produce a population of 19 million individuals
  after 750 years if all offspring survived to
  reproductive maturity and fostered their normal
  number of offspring.

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• 2) Members of a population compete for survival.
• Population sizes remain stable- populations
  generally fluctuate around a constant size.
• Resources are limited. Resources such as food,
  water, light dont increase as populations grow
  larger.
• Eventually, the needs of a growing population
  will exceed the available resources.
• As a result, individuals must compete for
  resources.
• Influenced by Thomas Malthus 1798 essay on
  human population much of human suffering-
  disease, famine, homelessness, and war- was the
  inescapable consequence of the potential for the
  human population to increase faster than food
  supplies and other resources.

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• 3) Genetic variability exists among individuals
  in a population.
• Most traits reveal considerable variety in their
  form.
• Ex. Musculature, height, fur color, hair color,
  skin color, eye color, etc.

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Figure 22.9 A few of the color variations in a
population of Asian lady beetles
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• 4) Some individuals will be better suited for
  their environment. Only the most fit individuals
  survive. survival of the fittest
• Individuals with traits best adapted for
  survival in the environment are able to
  out-compete other individuals for resources.

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• 5) Individuals with the better adaptations
  survive and leave offspring who inherit the
  traits of their parents.
• In turn, the best adapted of these offspring
  leave the most offspring.
• Over time, traits best adapted for survival in
  the environment and the alleles that generate
  them accumulate in the population.
• Evolution occurs as advantageous traits
  accumulate.

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Figure 22.10 Camouflage as an example of
evolutionary adaptation
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Weedy/ Leafy Sea Dragon
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Key Points of Natural Selection

1. Populations (groups of interbreeding individuals
   belonging to a particular species and sharing a
   common geographic area) are the smallest unit
   that can evolve. Evolution is measurable over
   successive generations.
2. Natural selection acts only on heritable
   variations/phenotypes. (not acquired ones)
3. Natural selection is situational as environmental
   factors vary from place to place and from time to
   time. An adaptation in one situation may be
   useless or even detrimental in another situation.

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EVIDENCE FOR EVOLUTION(five scientific
disciplines agree)

• Paleontology provides fossils that reveal the
  prehistoric existence of extinct species. As a
  result, changes in species and the formation of
  new species can be studied.
• Fossil deposits are often among sediment layers.
• Law of superposition states that the deepest
  layer of earth contains the oldest specimens.

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• 2. Biogeography uses geography to describe the
  distribution of species.
• Has revealed that unrelated species in different
  regions of the world look alike when found in
  similar environments.
• Provides strong evidence for the role of natural
  selection in evolution.
• Ex. Wallaby (marsupial) and Rabbit (placental)
• flying squirrel-sugar glider

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• 3. Embryology is the study of embryos and their
  development.
• Reveals similar stages in development (ontogeny)
  among related species.
• The similarities help establish evolutionary
  relationships (phylogeny).
• Ex. Gill slits and tails are found in fish,
  chicken, pig, and human embryos. These species
  are all vertebrates.

Haeckel exaggerated these Sketches. Not as
similar as shown.
Ontogeny recapitulates Phylogeny is not
correct.
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• 4. Comparative anatomy describes three kinds of
  structures that contribute to the identification
  of evolutionary relationships among species.
• Compares external morphology and internal anatomy
• Ex. Homologous structures are body parts that
  are structurally similar in related species.
  Serve different functions have been modified by
  different natural selection from the common
  ancestor.

These homologous structures are anatomical
evidence of descent with modification.
Modified for grasping, walking, Swimming, flight
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• homologous structures reveal common ancestry and
  a pattern of evolution called DIVERGENT EVOLUTION.

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• Ex) Vestigial organs organs with no apparent
  function or purpose imply evolutionary
  relationships to primitive ancestors.
• May still be around as an evolutionary relic.
• The structure served a purpose in an ancient
  ancestor but no longer does.
• Example pelvic girdle, hind leg bones in whales
• Tail bone in humans.

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Figure 22.17 A transitional fossil linking past
and present
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• Ex) Analagous Structures are body parts similar
  in function but not in structure.
• Not because they have evolved from a common
  ancestor
• Instead, because they evolved these similar
  adaptations independently because they evolved in
  similar environments with the same selection
  pressures.

For example the finned, streamlined, fat
insulated bodies of Sharks, Penguins,
Porpoises are all adaptations for a life of
swimming in the seas.
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Humming bird
Hummingbird Moth
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• 5) Molecular Biology examines the nucleotide and
  amino acid sequences of DNA and proteins from
  different species.
• Closely related species share higher percentages
  of sequences than distantly related species.
• All living things share the same genetic code.
• Favors evolution of different species through
  modification of ancestral genetic information.
• For example, more than 98 of the nucleotide
  sequences in humans and chimpanzees are identical.

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THE MODERN SYNTHESIS

• The incorporation of genetics into
  evolutionary thinking created a more
  comprehensive view of evolution called
  neo-Darwinism or the modern synthesis.
• You will study evolution from a genetic point of
  view in the next chapter.

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Historical examples that support the theory of
natural selection

1. Pesticide resistance
2. Antibiotic resistance
3. HIV
4. Industrial Melanism the peppered moth
5. Sickle Cell Anemia- Malaria

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• 6) ARTIFICIAL SELECTION
• Humans make breeding choices among livestock,
  crops, dogs, horses, etc.
• drive evolution.

Cattle breeders, ancient africa
Wild mustard
Cabbage, broccoli, brussel sprouts, cauliflower
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The Origin of Species was truly radical for its
time

• Darwin waited more than 20 years to publish.
• Challenged prevailing scientific views.
• Shook the deepest roots of Western culture.
• Contrasted with the conventional paradigm of an
  Earth only a few thousand years old, populated by
  unchanging forms of life which had been
  individually made during a single week by the
  Creator (along w/ entire universe).

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The Origin of Species

• Darwin continued to gather evidence for nearly 20
  years.
• Lyell cautioned Darwin to publish before someone
  beat him to it.
• 1858 Alfred Wallace developed a theory of natural
  selection and sent it in a letter to Darwin- it
  was presented at a conference that year.
• Darwin quickly finished Origin of Species and
  published it the following year- 50 years after
  Lamarck published his ideas .
• Darwins theory that natural selection, or
  survival of the fittest, was the driving force
  of evolution is now called Darwinism.
• Descent with modification was used instead of the
  word evolution in his book (until the very last
  page).

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Descent with Modification

• Unity in life
• All organisms related through descent from some
  unknown ancestor that lived in the remote past
• As the descendants of those ancestral organisms
  spilled into various habitats over millions of
  years, they accumulated diverse modification, or
  adaptations, that fit them to specific ways of
  life.

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Descent With Modification means evolution
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