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EVOLUTION
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
biodiversity.
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
vegetation

The higher islands had greater rainfall and
a different assortment of plants and
animals-Isabela- Island had rich
vegetation.
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
inhabited.
Animals found in the Galapagos

Land Tortoises

Darwin Finches

Blue-Footed Booby

Marine Iguanas
Animals
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
Lamarck
Population Growth


Thomas Malthus19th century English
economist
If population grew
(more babies born
than die)
 Insufficient living
space
 Food runs out
 Darwin applied this
theory to animals
Natural Selection & Artificial
Selection

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
useful.
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
environment
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
fossils
Someone’s idea of a joke!
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ButBiology
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
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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
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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?
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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
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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
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Analogous structures
 Dolphins: aquatic mammal
 Fish: aquatic vertebrate
both adapted to
life in the sea
 not closely related

Watch the tail!
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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!
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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
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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
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Comparative Embryology
Human
Mouse
Bat
Chicken
Alligator
3. Molecular record
 Comparing DNA & protein structure

everyone uses the same genetic code!
 DNA
Human
Macaque
Dog Bird
Frog
Lamprey
8
32 45
67
125
 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
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Building “family” trees
Closely related species are branches on the tree —
coming from a common ancestor
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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

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Selective Breeding
Humans create the
change over time
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“descendants”
of the wolf
Artificial Selection
…and the
examples
keep coming!
I liked
breeding
pigeons!
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Artificial Selection gone bad!
 Unexpected
consequences of
artificial selection
Pesticide resistance
Antibiotic resistance
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Insecticide resistance
 Spray the field, but…
insecticide didn’t
kill all individuals
 What caused the
variation?

 mutation
resistant survivors
reproduce
 resistance is inherited
 insecticide becomes
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less & less effective

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Any Questions??
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