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Chapter 15
Darwin’s Theory of Evolution
Question of the day
 What was the name of
Darwin’s Boat?
 H.M.S. Beagle
 Where did it go?
 All over the world and
back.
Ch. 15 Essential Questions
 Why did Darwin
explore the world?
 Who shaped
Darwin’s thinking?
 What is Artificial &
Natural Selection?
 What is Evolution?
15-1 Evolution
 What is Evolution?
 Change over time
 Darwin - Modern
organisms descended
from ancient ones
 He found enough
evidence to make a
theory
Darwin’s
Travels
 Originally voyage
was to survey Brasil
and S.A.
 Not intended for
scientific study
 Darwin was along for
the ride
 Visited places like:
 Galapagos Islands
 Falkland Islands
 Tahiti
Darwin’s Observations
 Patterns of Diversity
 Organisms were different
between islands
 They were well adapted to
environment
 Organisms & Fossils
 Found preserved remains that
resembled modern species
 Specialization
 Organisms developed special
traits or habits to survive in an
area
Darwin’s Influences
 Hutton & Lyell
 Geology
 Evolution of Earth’s
environment
 By natural events
 Time, disasters,
weathering, etc.
Darwin Thanks Lamark
 Darwin “borrows”
theories from naturalist
 Organisms evolve to be
more complex & perfect
 Use or disuse of limbs,
behaviors
 Inheiritance of acquired
traits - longer legs,
brighter feathers
 (Example: fiddler crabs,
giraffes)
Darwin’s Friend Malthus
 Thomas Malthus Economist
 Population Growth
 Resources are finite
 Not enough for
everyone
 Life History Theory
 Or difference in life
spans (clams vs.
humans)
Question of the Day
 How does Darwin
determine how
ancestors are related
between 2 species?
 He looks at homologous
structures, early
development of
embryos
15-3 Darwin’s Case
 The Origin of
Species. Book by
Darwin
 Talked about all his
findings
 Evolution has taken
place for millions yrs
 Will continue in the
future
Natural Variation
 Darwin said
species are not
perfect &
unchanging
 Called NATURAL
VARIATION
(differences among
individuals)
 Example aquilegia, human
skin color, etc.
Artificial Selection
• Selective
Breeding
• Choosing the
individuals
unnaturally to
yield best results
or variation
• Example - Cross
Breeding of Dogs
Natural Selection Evolution
 Darwin’s Theory of
Evolution
 Struggle for Existence makes individuals of
species compete for life
(food, living space,
mates
 Survival of the Fittest ability for individual to
adapt & thrive in its
environment
More Natural Selection
 Survival of the Fittest
takes many forms:
 Not just biggest, fastest
or strongest
 Can be BEHAVIORS:
 Smarter (Bigger Brain)
 Teamwork (working or
living in families)
More Natural Selection
 Descent with Modification species adapt to a NICHE
different from ancestors
 Niche - The function an
organism within a community
or particular area within a
habitat occupied by an
organism.
 All Big Cats:
 Descended from common
ancestor
 Made own niche
Evidence of Evolution
 How did Darwin know
things were evolving?
 The Fossil Record distribution of ancient life
remains
 Geographic Distribution of
Species - where in the world
a species developed
 Homologous Body Structures
- similar body parts of
ancestors or similar species
 Early Development
Characteristics - embryos &
fertilized growth
Darwin’s Theory Summarized
 Individuals in nature are different
(Natural Variation)
 Organisms in nature produce more
offspring than can survive
(Struggle for existence)
 Organisms compete for limited
resources (Survival of Fittest)
 Individuals best suited for
environment will be most
successful (natural selection)
 Species evolve over time & from
common ancestors (Evolution,
Common Descent & Descent w/
Modification)
Final Thoughts on Evolution
 Where is the future of
evolution headed?
 Was Darwin right?
 Could there be
Devolution?
 I say no because of all
the scientific evidence
 But You need to make
up your mind