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Chapter 4 & 5
Organic Evolution
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Before Darwin
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Jean Baptiste Lamarck
Lamarckism:
inheritance of
acquiredcharacteristics
Transformational
view of evolution
Not supported.
1744-1829
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Sir Charles Lyell
Uniformitarianism
Laws of physics and
chemistry remain thesame
Natural processes
which acted in the
past will continue to
act.
1797-1875
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Thomas Malthus
Concerned with
human population
growth People tended to
reproduce faster
than their food
supply, and areforced to compete for
existence.1766-1834
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Charles Darwin
Naturalist who
combined the ideas
of Malthus, Lyell andothers to form the
theory of evolution.
1809-1882
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DARWINS THEORY OF EVOLUTION
A sea voyage helped Darwin frame histheory of evolution
On his visit to the Galpagos Islands
Charles Darwin observed many uniqueorganisms
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Darwins main ideas can be traced back to
the ancient Greeks
Aristotle and the Judeo-Christian culture
believed that species are fixed
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In the century prior to Darwin the study of
fossils suggested that life forms change
Geologists proposed that a very old Earth is
changed by gradual processes
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While on the voyage of the HMS Beaglein the
1830s Charles Darwin observed similarities
between living and fossil organisms and the
diversity of life on the Galpagos Islands
North
AmericaEurope
Great
Britain
Africa
Equator
Asia
Australia
TasmaniaNew
Zealand
PACIFIC
OCEAN
ATLANTIC
OCEAN
PACIFIC
OCEAN
PACIFIC
OCEAN
The
Galpagos
Islands
South
America
Tierra del Fuego
Cape Horn
Cape of
Good HopeAndes
Pinta
MarchenaGenovesa
EquatorSantiago
Isabela
Fernandina
Florenza Espaola
San
Cristobal
Santa
CruzSanta
Fe
Pinzn
Daphne
Islands
40 miles
40 km0
0
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Darwins experiences during the voyage of
the Beaglehelped him frame his ideas on
evolution
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Evolution
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Evolution
Change over time: Organic or biological
evolution is a series of changes in the
genetic composition of a population overtime.
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Adaptation
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Adaptation
Occurs when a heritable change in a
phenotype increases an animals chance
of successful reproduction.
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Adaptation
Occurs when a heritable change in a phenotype
increases an animals chance of successful
reproduction.
Likely to be expressed when an organism
encounters a new environment.
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Adaptation
Occurs when a heritable change in a phenotype
increases an animals chance of successful
reproduction. Likely to be expressed when an organism
encounters a new environment.
Not every characteristic is an adaptation
to some kind of environmetal situation.
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Adaptation
Occurs when a heritable change in a phenotype
increases an animals chance of successful
reproduction.
Likely to be expressed when an organism encounters a
new environment.
Not every characteristic is an adaptation to some kind
of environmetal situation.
A No No: evolutionary adaptations lead
to perfection.
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Darwinian Evolutionary Theory:
The Evidence1) Perpetual change
2) Common descent
3) Multiplication of species
4) Gradualism
5) Natural selection
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I. Perpetual Change
Darwin noticed fossils of extinct marine
organisms thousands of feet above present day
sea level.
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The Burgess Shale
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Before the Scientific Method People based their beliefs on
their
interpretations of what they saw
Without testing their ideas
Rather, their conclusions were based on
untested observations.
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Snakestones!
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Some fossils you can not refute.
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The Baltic amber deposits range between 35 to 40
million years old and is the largest source of amber
yet discovered.
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So What do these Fossils tell us?
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Geological Time
Long before the earths age was known,
geologists divided its history into a table
of succeeding events based on theordered layers of sedimentary
rock.
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The fossil record reveals that organisms
have evolved in a historical sequence
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Evolutionary trends
The fossil record allowed Darwin to view
evolutionary change across the broadest
scale of time.
Animal species typically survive
approximately 1 million to 10 millionyears, before going
extinct.
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I. Perpetual Change
Darwin noticed fossils of extinct marine organisms
thousands of feet above present day sea level.
Darwin also worked on the change of animals
under domestication by humans (artificial
selection).
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Darwin found convincing evidence for his
ideas in the results of artificial selection
The selective breeding of domesticated
animals
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I. Perpetual Change
Darwin noticed fossils of extinct marine organismsthousands of
feet above present day sea level.
Darwin also worked on the change of animals underdomestication
by humans (artificial selection).
He combined these two observations to form
the idea that organisms are constantlychanging through time.
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II. Common Descent
Whereas Lamarck believed in multiple
origins of life, Darwin believed that all
life originated from a single commonancestor.
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Darwin proposed that living speciesare
descended from earlier life forms
Thousands to
millions of years
of natural selection
Ancestral canine
African wild dog Coyote Wolf Fox Jackal
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Hi There How are You!!!
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How many species of horses are there?
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Grevy's Zebra (Equus grevyi)
Burchell's Zebra (Equus burchelli) Mountain Zebra (Equus
zebra)
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Asiatic Wild Asses
- Kulan and Onager (Equus hemionus)
- Kiang (Equus kiang)
African Wild Asses
- African Wild Ass (Equus asinus)
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Przewalski's Horse (Equus caballus)
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So what do these horse fossils
suggest?
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Throughout the history of all forms of
life, evolutionary processes generate new
characteristics that are then inherited bysubsequent
generations.
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II. Common Descent
Whereas Lamarck believed in multiple origins of life,
Darwin believed that all life originated from a single
common ancestor.
The evidence Darwin used was
homology:
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Homologies
Homologies: Anatomical structures
within different organisms which
originated from a structure or trait oftheir common ancestral
organism.
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Vestigial Structures
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What are these animals?
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Analogous Structures
The evolution of superficially similar
structures in unrelated organisms is
called convergent evolution.
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So What?
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Theory of Common Descent is
Testable Like all good scientific theories, common
descent makes several important predictions
that can be tested and potentially used to reject
it.
According to this theory, we should be able to
trace the genealogies of all modern species
backward until they converge on ancestrallineages shared with
other species, both living
and extinct.
