1 • Chapter 22~ Descent with Modification: A Darwinian View of Life
Jan 19, 2016
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• Chapter 22~ Descent with Modification: A Darwinian View of Life
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I. Early Biology
• Scientists knew that organisms had changed
• Fossil evidence
• Age of the Earth
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Evolutionary history
• Linnaeus: taxonomy
• Hutton: gradualism
• Lamarck: evolution
• Malthus: populations
• Cuvier: paleontology
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• Lyell: uniformitarianism
• Darwin: evolution• Mendel: inheritance• Wallace: evolution
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Lamarck
• Changes from simple to complex
• Organisms want to adapt or change
• Acquired characteristics were inherited (passed on)
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Lamarck
• Later disproved
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II. Darwin• At 21, took a job as
a naturalist on the HMS Beagle
• Collected specimens, took notes of different organisms
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His voyage:
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II. Darwin
• Sailed to Galapagos Islands
• All new species, but similar to those found elsewhere
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• Finches most famous• Had slightly different beaks from island to island• Differed by their diet
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Descent with Modification, I• 5 observations: • 1- Exponential fertility
• 2- But Stable population size
• 3- Limited resources • 4- Individuals vary
• 5- Heritable variation
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Descent with Modification, II• 3 Inferences:
• 1- Struggle for existence
• 2- Non-random survival
• 3- Natural selection (differential success in reproduction)
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Evolution• Evolution:
the change over time of the genetic composition of populations
• Natural selection:populations of
organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success)
• Evolutionary adaptation: a prevalence of inherited characteristics that enhance organisms’ survival and reproduction
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November 24, 1859
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Natural Selection
• Over time variations become more frequent in population
• Results in population being different than ancestors
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EvolutionEvolution is the change in a population over time
Natural Selection - Remember the Giraffe?How did it get the long neck?
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Evidence of Change
• Biogeography• Fossil Record• Anatomy & Physiology• Embryology• Biochemistry
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Evolution evidence: Biogeography
• Geographical distribution of species
• Examples: • Islands vs. Mainland
– Australia vs. Continents
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Fossils
• Remains or traces of living organisms
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Physiology Mimicry-An adaptation
• Enables one species to resemble another species.
• Ex.-harmless species looks like a harmful one, good tasting vs. bad tasting.
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Anatomy- Homologous Structures
• Common evolutionary origin. • Similar in arrangement or
arrangement and function.• Example: forelimbs of a whale, a
crocodile and a bird wing.
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Anatomy- Analogous Structures
• No common evolutionary origin, but similar in function.
• Wings of a bat and wings of a butterfly.
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Anatomy- Vestigial Structures
• No function now but was probably useful to an ancestor.
• Ex. A whale has leg bones, a snake has leg bones
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Embryology
• Earliest stage of growth and development • Embryos of a fish, a chicken, a pig, a cow,
a rabbit, and a human are almost identical.• They all have gill slits and a tail.
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Biochemistry
• Comparisons of DNA and RNA • Now monera (prokaryotes) is divided into
two separate kingdoms based on their biochemistry.
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Evolution evidence: Molecular
Biology
• Similarities in DNA, proteins, genes, and gene products
• Common genetic code
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Final words…...
• “Absence of evidence is not evidence of absence.”