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Evolution
Understanding the
Diversity of Life – Part 1
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Evolution
“Nothing in
biology makes
sense EXCEPT in
the light of
evolution.”
Theodosius
Dobzhansky
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Charles Darwin in later years
History of Evolutionary
Theory
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Early Ideas about Earth’s Organisms
• Aristotle believed
species were fixed
creations arranged
by their complexity
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Early Ideas about Earth’s Organisms
Carolus Linnaeus
• 1st to group similar
organisms and
assign them Latin
names
• Two word name
(Genus species)
• Known as Binomial
nomenclature
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Early Ideas about Earth’s Organisms
Georges Cuvier
• Some species’ fossil records
disappeared in more recent
layers
• Stated that species disappear
due to a catastrophic event of
the earth’s crust
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Early Ideas about Earth’s Organisms
James Hutton & Charles Lyell
• Stated that various
geological forces constantly
changed the planet
• Changes in Earth’s crust
were due to slow
continuous processes
• Idea Known as Gradualism
or Uniformitarianism
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Early Ideas about Earth’s Organisms
Hutton & Lyell, cont.
• Geological
processes moved at
uniform rates;
building & wearing
down Earth’s crust
• Proposed that the
Earth was millions
of years instead of
a few thousand
years old
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Early Ideas about Earth’s Organisms
Reverend Thomas Malthus
• Studied macroeconomics
• Stated that populations
could not grow indefinitely
• This growth would be
stopped by:
1. Disease
2. Famine
3. War
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Lamarck’s Theory of Evolution
Jean-Baptiste Lamarck
• One of first scientists to
understand that organisms
change over time
• Put forth an idea called
Inheritance of Acquired
Characteristics through
Law of Use and Disuse
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Lamarck’s Theory of Evolution
• Proposed that by selective use or disuse
of organs, organisms acquired or lost
certain traits during their lifetime
Examples:
blacksmiths & their sons (muscular arms)
giraffe’s necks longer (from stretching)
• These traits could then be passed on to
their offspring
• Over time this would lead to new species
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Lamarck’s Mistakes
Inheritance Of Acquired Traits
• Traits Acquired During Ones Lifetime
Would Be Passed To Offspring
• If true, clipped ears would pass to
offspring!
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Lamarck’s Mistakes
• Lamarck did NOT know how traits were
inherited (traits are passed through
genes)
• Genes are NOT changed by activities in
the life of an organism
• Change occurs through mutations of
genes
• These mutations occur before the
organism is born
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Charles Darwin the
Naturalist
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Charles Darwin
• Born Feb. 12, 1809
• A naturalist
• Collector/identifier of
plant and animal
specimens
• Formed his ideas about
evolution sailing on the
HMS Beagle for the
Galapagos Island in
1831
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The Galapagos Islands
• Small group of
islands 1000 km
west of Ecuador
• Very different
climates and
geography on each
island
• Animals on each of
the islands similar
but unique
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The Galapagos Islands
• Islands all formed by action of volcanoes
• Island species varied from mainland species &
from island-to-island species
• Each island had long or short neck tortoises
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The Galapagos Islands
• Finches on the islands resembled a
mainland finch
• Different types of finches appeared on
the islands where the available food was
different (seeds, nuts, berries, insects…)
• Finches had beaks adapted to their type
of food gathering
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The Struggle for
Existence
Darwin’s Observations and
Conclusions
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Darwin’s Observations
• Patterns of Diversity
• Unique adaptations in
organisms
• Species not evenly
distributed
• Examples:
Australia: kangaroos
South America: llamas
Africa: elephants
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Darwin’s Observations
• Darwin collected
living organisms and
fossils on his voyage
• Took these back to
England to study
This species NO longer existed.
What had happened to them?
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Giant
Ground
Sloth
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Glyptodon – Ancestor of Modern Armadillo
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Darwin’s Observations
• Unlimited resources will allow
organisms increase
exponentially, generation to
generation
• In nature, populations tend to
remain stable in size
• Environmental resources are
what limits population size
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Darwin’s Observations
•Individuals of a
population vary in
their characteristics
with no two individuals
being exactly alike.
•Much of this variation
between individuals is
inheritable.
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Darwin’s Conclusions
•Production of more
individuals than can be
supported by the
environment leads to a
struggle for existence
•Only a fraction of offspring
survive each generation
•He called this “Survival of
the Fittest”
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Darwin’s Conclusions
•Individuals who
inherit characteristics
most fit for their
environment are
likely to leave more
offspring than less fit
individuals
•He called this
“Natural Selection”
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Ideas that Shaped
Darwin’s Thinking
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Ideas that Shaped Darwin’s
Thinking
Hutton & Lyell
• Expanded Earth’s age from 6000 to
billions of years
• Explained geological processes that
shaped the earth
• Helped Darwin understand the presence
of sea shells in the Andes mountains at
12,000+ feet
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Ideas that Shaped Darwin’s
Thinking
Malthus’ Influence
• Babies are born faster than people die
• Total population size limited by resources
such as the food supply
• High birth rates & limited resources
would force life & death competition
• Each Species Struggles For:
• Food
• Living Space
• Mates
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Darwin’s Theory of
Evolution
Organisms Change Over Time
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Evolution:
Defined
•Evolution is the
slow , gradual
change in the
alleles of a
population over
time
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Darwin’s Theory of Evolution
•The unequal ability of individuals to
survive and reproduce leads to a gradual
change in a population, with favorable
characteristics accumulating over
generations (Natural Selection)
•This creates new species
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Darwin’s Theory of Evolution
Descent with
Modification:
• Organisms descended
from common
ancestors
• Organisms change
with time, diverging
from a common form
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Darwin’s Theory of Evolution
Natural Selection:
• Driving force for
evolution
• During the struggle for
resources, strongest
survive & reproduce
• Idea that at least some
of the beneficial
differences between
individuals are
inheritable
.
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Publication of:
“On The Origin of Species”
• Upon his return To England, Darwin spent
25 years developing his observations into
the Theory of Evolution
• He hesitated to publish because:
1. He knew that his theory would be extremely
controversial and would be attacked
2. His theory challenged established religious &
scientific beliefs; particularly about the Creation
of Man
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“O’ no you didn’t! This was my
Idea!” - Darwin
Alfred Russel Wallace
• Fellow naturalist
• Sent an essay of his work to
Darwin to review
• Had independently come to the
conclusion that species
changed over time because of
their struggle for existence
• When Darwin read Wallace’s
essay, he knew he had to
publish his findings
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Publication of:
“On The Origin of Species”
• Darwin presented Wallace’s essay & some
of his work at a conference in July of 1858
• Then he started work on his book “Origin
of Species” which was published in 1859
• Spent the rest of his life refining his ideas
about evolution
• Darwin died in 1882, the father of 10
children; 7 survived to adulthood
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