Chapter 15: Darwin’s 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
 1831 Darwin traveled on the Beagle
 A 5-year expedition to South America and South Pacific for mapping and
collecting specimens.
 His job was to collect, study and store biological specimens
 His observations in the Galapagos Islands were among his most important
 Compared the anatomy of many species of reptiles, insects, birds, plants
 Darwin’s observations
 He noticed organisms were unique yet similar to species seen in other parts of
the world
 Grasslands in some regions were similar to one another but were inhabited by
very different animals.
 The Galapagos Islands were close together but had very different climates.
 The shape of the giant tortoises shell and neck length can identify which island a
tortoise inhabited
 The shape of the finches beak varied from island to island
 By the end of his trip he was convinced that evolution occurs, that species can
and do change
 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
 Only the strongest survive and the weak die
15.2 Ideas that Shaped Darwin’s Thinking
 Hutton
 Earth is shaped by geological forces over long periods of time
 Estimates earth to be millions, not thousands of years old
 Lyell
 Processes occurring now have shaped Earth’s geological features over long
periods of time
 Lamarck
 Inheritance of Acquired Traits
 Also called use and disuse theory
 Selective use or disuse of organs, organisms acquired or lost certain traits
during their lifetime
 Those traits could be passed on to offspring
 Ex. Long necks of giraffes
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Big muscles
 Evaluating Lamarck’s Hypotheses
 Lamarck’s hypotheses of evolution are incorrect in several ways.
 Lamarck did not know how traits are inherited
 However, he paved the way for the work of later biologists.
 Malthus
 If the human population continued to grow unchecked, sooner or later there would
be insufficient living space and food for everyone.
 This information was central to Darwin’s explanations of evolutionary change.
15.3 Darwin Presents his Case
 Publication of Origin of Species
 Darwin wrote all of his ideas down, but did not publish them.
 He struggled with his ideas because they went against scientific thought at the
time
 Wallace was a naturalist that had the same ideas as Darwin and was going to
publish them.
 This forced Darwin to publish his ideas
 On the Origin of Species publish in 1859
 Inherited Variation and Artificial Selection
 One of Darwin’s most important ideas was that organisms of the same species
vary from one another
 Darwin thought that variation mattered
 Artificial Selection – a breeder selects particular traits. This had been done by
farmers for years
 Darwin wondered if nature selected particular traits
 The struggle for existence
 Individuals with characteristics that are not well suited to their environment
either die or leave few offspring.
 Individuals that are better suited to their environment survive and reproduce
most successfully.
 Natural Selection – organisms with favorable variations survive, reproduce and
pass those variations on to the next generation
 Darwin also called this “Survival of the Fittest”
 Evidence of Evolution
1. Fossil Record
 Darwin say 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
PIC
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3. Analogous Structure
 Do not have a common evolutionary origin
 Any body structure that is similar in function but different in structure
 Example: butterfly 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
PIC
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Chapter 15: Darwin’s Theory of Evolution
15.1 The Puzzle of Life’s Diversity
 Evolution –
 Charles Darwin

 Considered to be the father of evolutionary theory
 Born
 Voyage of the H.M.S. Beagle
 1831 Darwin traveled on the Beagle
 A _____ year expedition to South America and South Pacific for mapping and
collecting specimens.
 His job was to collect, study and store biological specimens
 His observations in the _______________ _______________ were among his
most important
 Compared the anatomy of many species of reptiles, insects, birds, plants
 Darwin’s observations
 He noticed organisms were unique yet similar to species seen in other parts of
the world
 Grasslands in some regions were similar to one another but were inhabited by
very different animals.
 The Galapagos Islands were close together but had very different ____________
 The shape of the giant tortoises ____________ and ________ ________can
identify which island a tortoise inhabited

4
 By the end of his trip he was convinced that _______________ occurs, that
species can and do change
 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

15.2 Ideas that Shaped Darwin’s Thinking
 Hutton

 Estimates earth to be _______________, not thousands of years old
 Lyell
 Processes occurring now have shaped Earth’s geological features over
__________ periods of time
 Lamarck
 Inheritance of Acquired Traits
 Also called
 Selective use or disuse of organs, organisms acquired or lost certain traits
during their lifetime

 Ex.
 Evaluating Lamarck’s Hypotheses
 Lamarck’s hypotheses of evolution are incorrect in several ways.

 However, he paved the way for the work of later biologists.
5
 Malthus
 If the human population continued to grow unchecked, sooner or later there would
be insufficient living space and food for everyone.
 This information was central to Darwin’s explanations of evolutionary change.
15.3 Darwin Presents his Case
 Publication of Origin of Species
 Darwin wrote all of his ideas down, but did not publish them.
 He struggled with his ideas because they went against scientific thought at the
time
 Wallace was a naturalist that had the same ideas as Darwin and was going to
publish them.
 This forced Darwin to publish his ideas
 On the Origin of Species publish in __________
 Inherited Variation and Artificial Selection
 One of Darwin’s most important ideas was that organisms of the same species
vary from one another
 Darwin thought that variation mattered
 Artificial Selection –
 Darwin wondered if nature selected particular traits
 The struggle for existence

 Individuals that are better suited to their environment survive and reproduce
most successfully.
6
 Natural Selection –
 Darwin also called this “____________ ____ _____ ____________”
 Evidence of Evolution
1. Fossil Record
 Darwin saw _____________ as a record of the history of life on Earth.
2. Homologous Body Structures


 Example:
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3. Analogous Structure

 Any body structure that is similar in function but different in structure
 Example:
 Can’t be used to indicate evolutionary relationships, but they do provide evidence
of evolution
4. Vestigial Structure

 Example:
5. Similarities in Embryology

 Similarities among vertebrate embryos suggest evolution from a
______________ ________________
 These common cells and tissues, growing in similar ways, produce homologous
structures
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