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Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
15.2 Evidence of Evolution
15.3 Shaping Evolutionary Theory
15.1 Darwin’s Theory of Natural Selection
! Main idea: Charles Darwin developed a theory of
evolution based on natural selection
! Objectives
n  Discuss the evidence that convinced Darwin
that species could change over time.
n  List the four principles of natural selection.
n  Show how natural selection could change a
population
! New Vocabulary
n 
Selective breeding, Artificial selection, Natural
selection, Evolution
Developing the Theory of
Natural Selection
! Charles Darwin boarded
the HMS Beagle in 1831.
! Most believed the world
was about 6,000 years old.
! During the ship’s five year
voyage, Darwin made
extensive collections of
rocks, fossils, plants and
animals.
! He also read Charles Lyell’s Principles of
Geology – a book proposing the Earth
was millions of years old.
Developing the Theory of
Natural Selection
HMS Beagle
! In 1835, the Beagle arrived in the
Galapagos Islands off the coast of South
America.
! Darwin began to collect mockingbirds,
finches, and other animals on the four
islands.
! He noticed that the different islands
seemed to have their own, slightly different
varieties of animals.
Developing the Theory of
Natural Selection
Galápagos Islands
! Almost every
specimen that
Darwin had
collected on
the islands
was new to
European
scientists.
! Darwin suspected populations from the mainland
changed after reaching the Galápagos.
Developing the Theory of
Natural Selection
! Darwin hypothesized that new species
could appear gradually through small
changes in ancestral species.
! Darwin inferred that if humans could
change species by artificial selection
(selective breeding), then perhaps the
same process could work in nature.
Developing the Theory of
Natural Selection
Natural Selection
! Darwin called his theory Natural Selection
! He reasoned that,
given enough time,
natural selection could
modify a population
enough to produce a
new species.
Basic Principles of Natural Selection
Principle
Example
1.  Variation: Individuals in a
population differ from one
another.
Students in this class look different.
2.  Heritability: Variations are
inherited from parents.
Tall sunflowers produce tall
sunflowers, short sunflowers
produce short sunflowers.
3.  Overproduction: Animals have The average cardinal lays nine eggs
more young than can survive on per summer. If each baby cardinal
the available resources
survived and reproduced once, in 8
years there would be one million
cardinals from the original pair.
4.  Reproductive Advantage:
Variations that increase
reproductive success will be
more common in the next
generation.
If having a fan-shaped tail increases
reproductive success of pigeons,
then more pigeons in the next
generation will have fan-shaped
tails.
The Origin of Species
! Darwin published On the Origin of Species
by Means of Natural Selection in 1859.
! Today, biologists use the term evolution to
define changes in groups of organisms
through time.
! Darwin’s theory of natural selection is
NOT the same as evolution. Natural
selection is a means of explaining HOW
evolution works.
15.2 Evidence of Evolution
! Main idea: Multiple lines of evidence support the
theory of evolution.
! Objectives:
n  Describe how fossils provide evidence of
evolution.
n  Discuss morphological evidence of evolution.
n  Explain how physiology and biochemistry
provide evidence of evolution.
! New Vocabulary
n  Derived trait
n  Ancestral trait
n  Homologous structure
n  Vestigial structure
n  Analogous structure
n 
n 
n 
n 
Embryo
Fitness
Mimicry
Camouflage