WHAT IS EVOLUTION?
•  Change over time.
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WHAT IS BIOLOGICAL
EVOLUTON?
•  Changes in the genetic makeup of a
population of organisms over time !
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A FACT
•  Biological organisms evolve
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3
A FACT
•  Biological organisms evolve
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4
A FACT
•  Biological organisms evolve
•  The details are under discussion
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ANOTHER FACT
•  Nature does not have a plan; it is more
like a blind watch maker
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WHAT IS ADAPTATION?
Def’n - properties of an organism
that allow it to survive and
reproduce.
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ANOTHER FACT
•  At present, evolutionary theory is the
ONLY unifying theory in biology
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WHAT IS A THEORY?
•  A coherent system of general
propositions.
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FATHERS OF THEORY OF
NATURAL SELECTION
•  Charles Darwin
•  Alfred Russell Wallace
•  Patrick Matthew
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THEORIES GET ACCEPTED
AS A FUNCTION OF:
•  Supporting evidence
•  Current views on the matter
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DEFINING SPECIES
Def’n - a group of actual or potentially
interbreeding organisms
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REMEMBER:
•  When we speak of evolution, we mean
change across but not within
generations. The latter is referred to as
ontogeny.
From The World Book (TM) Multimedia Encyclopedia (c) 1999 World
Book, Inc., 525 W. Monroe, Chicago, IL 60661. All rights reserved. "
World Book illustration by Richard Lewington, The Garden Studio, London
1952
evolution
From The World Book (TM) Multimedia Encyclopedia (c) 1999 World
Book, Inc., 525 W. Monroe, Chicago, IL 60661. All rights reserved. "
World Book illustration by Richard Lewington, The Garden Studio
1990
13
DARWINIAN DEFINITION
OF EVOLUTION:
•  Def’n - Descent with modification.
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THE FIVE STAGES OF
EVOLUTIONARY BIOLOGY
•
•
•
•
•
Pre- Darwinian
Darwinian
Eclipse of Darwin
Modern Synthesis
Post-Modern
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LAMARCK’S
TRANSFORMATION THEORY
Species changed due to :
•  “Programmed” internal forces
•  Acquired characteristics
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LAMARK’S INTERNAL
FORCES THEORY
Trait
Value
sp 1
sp 2
time
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LAMARCK’S INHERITANCE
OF ACQUIRED CHARACTERS
•  Effects of unique events
get passed on to
offspring.
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CUVIER’S APPROACH
•  Whole species were frequently wiped
out by catastrophe and then,
miraculously, new ones appeared
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DARWIN’S VOYAGE 1831-6
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UNDENIABLY SIMILAR
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GALAPAGOS
MOCKINGBIRDS
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GALAPAGOS FINCHES
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ONE GREAT IDEA!
•  Various finches evolved from
a common ancestor
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FROM HIS READINGS,
DARWIN KNEW
•  Earth is very old - lots of time for change
•  Enormous reproductive potential for
organisms - why aren’t we covered in
flies?
•  Extant variation can be selected artificially
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A QUOTE:
•  “… Darwins’ view of Nature… kept faith
with the competitive, capitalist,
Malthusian dynamics of a poor-law
society and that his theory would make
him an ally of the middle and upper
class “
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A PROPOSAL
•  When together in a habitat, two similar
species do better when each specializes
on different resources
Seed
Size
Beak Size
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EVIDENCE FROM FINCHES
•  Compare alone vs. shared
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STICKLEBACKS
•  They come in different shapes and sizes
SHALLOW
DEEP
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INTERESTING PATTERN
•  When alone in lakes each species is
intermediate in size
•  When together in lakes each species
displays much more size extremes - benthic
species is much bigger and feeds deep and
the limnetic species is smaller and feeds
shallow
•  Coincidence?
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IS BEING EXTREME
BENEFICIAL?
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HOW THE STONEFLY GOT
ITS WINGS
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MISSING LINK?
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WEISMANN SHOWED
•  Acquired characters are NOT heritable
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THE BIG PROBLEM:
•  Linking Mendelian inheritance to natural
levels of within-population variability
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LEADERS OF THE MODERN
SYNTHESIS
•  R. Fisher
•  J. Haldane
•  S. Wright
From The World Book (TM) Multimedia
Encyclopedia (c) 1999 World Book, Inc.,
525 W. Monroe, Chicago, IL 60661. All
rights reserved. "World Book illustration
by Shirley Hooper, Oxford Illustrators
Limited
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BIG ACHIEVEMENT
•  Demonstration that it was that it was
mathematically possible to achieve
everyday patterns of variation without
having to resort to acquired
characteristics or hopeful monsters
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INDUSTRIAL MELANISM
•  evol_3
38
POST-MODERN FEATURES
•  Demonstration of inheritance mechanism
(birth of molecular biology)
•  Better integration of evolutionary and
ecological theory
•  Studies on the adaptive nature of behavior
(in the broad sense)
•  Studies on phenotypic plasticity
•  The species concept
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SCPECIES CONCEPT
•  OLD - A set of similar organisms
(measured against some time)
•  NEW - A group of interbreeding
organisms
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DARWIN’S THEORY IS
ELEGANT
•  It requires no demons to make it work!
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A SUMMARY OF DARWIN’S
THEORY
•
•
•
•
•
Organisms have enormous repro. potential
Their full potential isn’t being met
All populations contain variants
Some variants outperform others
If variation is heritable, they leave more
offspring and become more common
•  Given enough time, new species can arise
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DARWIN’S ALGORITHM
•  Substrate neutrality
•  Underlying mindlessness •  Guaranteed results. evol_3
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ALWAYS REMEMBER:
•  Can’t have evolution by Natural Selection
without variation
•  Can’t have evolution by Natural Selection
without variation being heritable
•  Natural Selection works on existing
variation i.e. it is not progressive
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THOUGHT EXPERIMENT 1:
SELECT FOR SIZE
NO VARIATION - NO EVOLUTION!!
45
THOUGHT EXPERIMENT 2:
SELECT FOR SIZE
HIGH
MEDIUM
10
LOW 3
0
NO HERITABILITY - NO EVOLUTION!!
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THOUGHT EXPERIMENT 3:
SELECT FOR SIZE
HIGH
MEDIUM
10
LOW 3
0
NO CONSISTANCY - NO EVOLUTION!!
47
THOUGHT EXPERIMENT 4:
SELECT DE NOVO FOR PATTERN CURRENT STOCK
GOAL
NO PROGRESSIVE EVOLUTION!!
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