Transcript Chapter 15

Chapter 15: The Theory of Evolution
15.1 The Puzzle of Life’s Diversity
• Evolution – change in a population of organisms over time
• Charles Darwin
• English Scientist
• Considered to be the father
of evolutionary theory
• Born Feb 12 1809
•
Voyage of the H.M.S. Beagle
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1831 Darwin traveled on the Beagle
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A 5-year expedition to South America and
South Pacific for mapping and collecting specimens
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His job was to collect, study and store biological
specimens
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His observations in the Galapagos Islands were among
his most important
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Compared the anatomy of many species of reptiles,
insects, birds, plants
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Darwin’s observations
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He noticed organisms were unique yet similar to
species seen in other parts of the world
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Grasslands in some regions were similar to one another
but were inhabited by very different animals.
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The Galapagos Islands were close together but had
very different climates.
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The shape of the giant tortoises shell and neck length
can identify which island a tortoise inhabited
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The shape of the finches beak varied from island to
island
Fig. 17.5b, p. 275
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By the end of his trip he was convinced that evolution
occurs, that species can and do change
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He knew that many species produce large numbers of
offspring and since Earth was not covered with many
species he suspected that there must be a struggle for
existence among individuals
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Only the strongest survive and the weak die
15.2 Ideas that Shaped Darwin’s Thinking
•Hutton
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Earth is shaped by geological forces over long periods
of time
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Estimates earth to be millions, not thousands of years
old
•Lyell
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Processes occurring now have shaped Earth’s
geological features over long periods of time
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Lamarck
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Inheritance of Acquired Traits
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Also called use and disuse theory
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Selective use or disuse of organs, organisms acquired
or lost certain traits during their lifetime
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Those traits could be passed on to offspring
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Ex. Long necks of giraffes
Big muscles
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Evaluating Lamarck’s Hypotheses
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Lamarck’s hypotheses of evolution are incorrect in several
ways.
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Lamarck did not know how traits are inherited
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However, he paved the way for the work of later biologists.
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Malthus
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If the human population continued to grow unchecked,
sooner or later there would be insufficient living space
and food for everyone.
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This information was central to Darwin’s explanations
of evolutionary change.
15.3 Darwin Presents his Case
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Publication of Origin of Species
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Darwin wrote all of his ideas down, but did not publish
them.
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He struggled with his ideas because they went against
scientific thought at the time
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Wallace was a naturalist that had the same ideas as
Darwin and was going to publish them.
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This forced Darwin to publish his ideas
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On the Origin of Species publish in 1859
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Inherited Variation and Artificial Selection
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One of Darwin’s most important ideas was that organisms
of the same species vary from one another
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Darwin thought that variation mattered
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Artificial Selection – a breeder selects particular traits.
This had been done by farmers for years
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Darwin wondered if nature selected particular traits
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The struggle for existence
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Individuals with characteristics that are not well suited
to their environment either die or leave few offspring.
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Individuals that are better suited to their environment
survive and reproduce most successfully.
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Natural Selection – organisms with favorable variations
survive, reproduce and pass those variations on to the
next generation
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Darwin also called this “Survival of the Fittest”
Evidence for Evolution
1. Fossil Record
• Darwin saw fossils as a record of the history
of life on Earth
2. Homologous Body Structures
•
Structural features with a common
evolutionary origin
• Similar in structure and/or function
• Example: whale forelimb, crocodile
forelimb, bird wing, human arm
STEM REPTILE
PTEROSAUR
CHICKEN
BAT
DOLPHIN
PENGUIN
HUMAN
3. Analogous Structure
• Do not have a common evolutionary origin
• Any body structure that is similar in function
but different in structure
• Example: butterfly wing and bird wing
• Can’t be used to indicate evolutionary
relationships, but they do provide evidence of
evolution
4. Vestigial Structure
• Any body structure that is reduced in
function in a living organism but may
have been used in an ancestor
• Example: appendix, wisdom teeth, tail
bone
5. Similarities in Embryology
• The early stages, or embryos, of many animals
with backbones are very similar
• Similarities among vertebrate embryos suggest
evolution from a common ancestor
• These common cells and tissues, growing in
similar ways, produce homologous structures
FISH
adult shark
REPTILE
BIRD
(chicken)
MAMMAL
(human)
Early human embryo (three
millimeters in length)
Fig. 20.7, p. 317