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Charles Darwin
Question for Thought
Earth has millions of other kinds of
organisms of every imaginable shape, size,
and habitat.
This variety of living things is called
How did all these different organisms arise?
How are they related?
In your own words, describe
what YOU think the theory of
evolution means…
Darwin’s Theory of Evolution
Evolution, or change over time, is the
process by which modern organisms have
descended from ancient organisms.
A scientific theory is a well-supported
testable explanation of phenomena that have
occurred in the natural world.
How do you think Darwin came
up with his theory?
Voyage of Beagle
Dates: February 12th, 1831
 Captain: Charles Darwin
 Ship: H.M.S. Beagle
 Destination: Voyage around the world.
 Findings: evidence to propose a
revolutionary hypothesis about how life
changes over time
The Galapagos Islands
The smallest, lowest islands were hot,
dry, and nearly barren-Hood Island-sparse
The higher islands had greater rainfall and
a different assortment of plants and
animals-Isabela- Island had rich
The Galapagos Islands
Darwin was fascinated in particular by the land
tortoises and marine iguanas in the Galápagos.
Giant tortoises varied in predictable ways from
one island to another.
The shape of a tortoise's shell could be used to
identify which island a particular tortoise
Animals found in the Galapagos
Land Tortoises
Darwin Finches
Blue-Footed Booby
Marine Iguanas
The Journey Home
 Darwin
Observed that characteristics
of many plants and animals vary
greatly among the islands
 Hypothesis:
Separate species may
have arose from an original ancestor
Population Growth
Thomas Malthus19th century English
If population grew
(more babies born
than die)
 Insufficient living
 Food runs out
 Darwin applied this
theory to animals
Natural Selection & Artificial
Natural selection-differences among
individuals of a species caused by nature
Artificial selection- nature provides the
variation among different organisms, and
humans select those variations they find
Evolution by Natural Selection
The Struggle for Existence-members of
each species have to compete for food,
shelter, other life necessities
Survival of the Fittest-Some individuals
better suited for the environment
Natural Selection
Over time, natural
selection results in
changes in inherited
characteristics of a
population. These
changes increase a
species fitness in its
Evidence of Evolution
The Fossil Record
Geographic Distribution of Living Things
Homologous Body Structures
Similarities in Early Development
We found the fossil — no joke!
Land Mammal
Complete series
of transitional
Someone’s idea of a joke!
the joke’s
on them!!
Ocean Mammal
Evolution from sea to land
 2006 fossil discovery of early tetrapod
4 limbs
 Missing link from sea to land animals
Regents Biology
3. Anatomical record
Animals with different
structures on the surface
But when you look under
the skin…
It tells an evolutionary story
of common ancestors
Regents Biology
Compare the bones
 The same bones under the skin
limbs that perform different functions
are built from the same bones
How could these
very different animals
have the
same bones?
Regents Biology
Homologous structures
 Structures that come from the same origin
 homo- = same
 -logous = information
 Forelimbs of human, cats, whales, & bats
same structure
 on the inside
same development in embryo
 different functions
 on the outside
evidence of common ancestor
Regents Biology
But don’t be fooled by these…
 Analogous structures
look similar
 on the outside
same function
 different structure & development
How is a bird
like a bug?
 on the inside
different origin
 no evolutionary relationship
Solving a similar problem with a similar solution
Regents Biology
Analogous structures
 Dolphins: aquatic mammal
 Fish: aquatic vertebrate
both adapted to
life in the sea
 not closely related
Watch the tail!
Regents Biology
Vestigial structures
 Hind leg bones on whale fossils
Why would whales
have pelvis & leg
bones if they were
always sea creatures?
Because they
used to
walk on land!
Regents Biology
Vestigial structures
 Structures on modern animals that have
no function
remains of structures that were functional
in ancestors
 evidence of change over time
 some snakes & whales have pelvis bones &
leg bones of walking ancestors
 eyes on blind
cave fish
 human tail bone
Regents Biology
Comparative embryology
 Development of embryo tells an
evolutionary story
similar structures during development
all vertebrate embryos have a “gill
pouch” at one stage of development
Regents Biology
Comparative Embryology
3. Molecular record
 Comparing DNA & protein structure
everyone uses the same genetic code!
Dog Bird
32 45
 compare common genes
 compare common proteins
number of amino acids different
from human hemoglobin
0 10 20 30 40 50 60 70 80 90 100 110 120
Regents Biology
Building “family” trees
Closely related species are branches on the tree —
coming from a common ancestor
Regents Biology
Artificial selection
 How do we know natural selection can
change a population?
we can recreate a similar process
 “evolution by human selection”
“descendants” of wild mustard
Regents Biology
Selective Breeding
Humans create the
change over time
Regents Biology
of the wolf
Artificial Selection
…and the
keep coming!
I liked
Regents Biology
Artificial Selection gone bad!
 Unexpected
consequences of
artificial selection
Pesticide resistance
Antibiotic resistance
Regents Biology
Insecticide resistance
 Spray the field, but…
insecticide didn’t
kill all individuals
 What caused the
 mutation
resistant survivors
 resistance is inherited
 insecticide becomes
Regents Biology
less & less effective
Regents Biology
Any Questions??
Regents Biology