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Evolution
Objectives:
1. Explain evidence for evolution
What evolution is NOT
• Not a theory (it is a fact, it has been observed
directly, and its extension to all life is supported
by more evidence than there is for the spherical
shape of planets, and there is no evidence against
it.
• Not something one should believe in (based on
science, not faith)
• Not concerned with the origin of life(only with
origin of species)
• Not concerned with the origin of humans
• Not discovered by Darwin
• Not the same as natural selection(the HOW of
evolution)
• Not something that happened only in the past
• Not something that happens to individuals
• Not an accidental or random process—
• Does not have any evidence against it
• Not contrived to undermine religion
• Does not deny the existence of God
• Does not conflict with religion (since it is
another way of trying to make sense of the
natural world, based on scientific observations
and critical analysis. Most religions have not
problem with evolution, and those that do
typically base their objections on an
inaccurate view of science and evolution
History of Evolution
• Aristotle—believed species
were fixed creations
arranged by their
complexity
• Believed for about 2000
years
Contributions to Evolution
• Charles Lyell—uniformitarianism—geologic
process still changing earth (sediment layers in
rock)
• Georges Cuvier—Catastrophism—species
extinction
• Thomas Malthus—resources—struggle for
existence
More Contributors
• James Hutton—Gradualism
• John Baptiste Lamarck—inheritance of
acquired traits—Law of use and disuse
• Alfred Russel Wallace—organisms evolved
from a common ancestor
Catastrophism
• Proposed by George Cuvier
• Studied fossils in the sedimentary rock strata
• Found some species completely disappeared
in more recent layers
• Though species disappeared due to
catastrophic events of the earths crust.
(volcano, earthquake, etc,)
Geological Change
• James Hutton studied invertebrate fossils
• Described the geological forces that have
changed life on earth over millions of years
ago (erosion, earthquakes, etc. )
• Changes in earths crust due to slow
continuous processes
• Gradualism
Uniformitarianism
• Charles Lyell
• Geological processes at uniform rates building
and wearing down Earth’s crust
• Proposed that the Earth was millions of years
old instead of thousands of years
The Dummy
• Lamarck—changes occur over time
• Stated that changes are adaptations to
environment acquired in an organisms lifetime
• Acquired traits are passed to offspring
More about the Dummy
• Law of Use and Disuse
• If a body part were used, it got stronger
• If not part was used, it deteriorated
Lamarck’s Theory of Evolution
Lamarck’s Mistakes
• Did not know how traits were inherited
• Genes are not changed by activities in life
• Change through mutations occur before an
organism is born
Evidence for Evolution Today
• Homologous Structures—same structure,
different function
More structures
• Analogous—different structure, same function
(fly wing and bat wing)…NOT evidence for
evolution
• Vestigial structure—remnant of organ from
Embryonic
Fetal Development
• Embryonic structures of different species
show significant similarities
DNA Sequence
Fossil Record
• Earth is billions of years old
• Fossils in different layers of rock showed
evidence of gradual change over time
Fossil Evidence
• Armadillo(N and S America)
• Glyptodon
Fossils
• Marine fossils found high in the Andes
mountains
Geographic Distribution of Living
Species
• Different animals on different continents but
similar adaptations to shared environments
Tomorrow…
• Darwin!
Divergent Evolution
• Accumulation of differences
between groups which lead
to the formation of a new
species, usually a result of
diffusion of the same
species to different and
isolated environments
which blocks the gene flow
and has new organisms
with different traits
Convergent Evolution
• Same traits acquired by unrelated organisms.
• Ancestors of bats and birds were land
creatures. They both evolved to have wings.
Darwin the Naturalist
• Born 1809
• Joined crew of HMS Beagle in 1831 for 5 year
voyage around the world
• Avid collector of flora and fauna
• Surprised by variety of life
The Galapagos Islands
• Small group of islands off the coast of South
America
• Each island has a very different climate
• Animals on each island are very unique
– Tortoises
– Iquana
– finches
The Galapagos Islands
• Volcanic islands
• Off the coast of Ecuador
Finches
• Finches on the islands resembled a mainland
finch.
• More types of finches appeared on the islands
where available food was different (seeds,
nuts, berries, insect, etc…)
• Had different beaks for the different foods
Darwin’s Observations and
Conclusions
•
•
•
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The struggle for Existence
Patterns of diversity
Unique adaptations of organisms
Both living organisms and fossils collected
Darwin’s Conclusions
• If left unchecked, the number of organisms of
each species will increase exponentially,
generation to generation
• In nature, populations tend to remain stable in
size
• Environmental resources are limited
Natural Selection
• Production of more individuals than can be
supported by the environment leads to a
struggle for existence among individuals
• Only a fraction of offspring survive each
generation
• Survival of the Fittest
Natural Selection
• Individuals who
inherit
characteristics
most fit for their
environment are
likely to leave
more offspring
than less fit
individuals
• Called Natural
Selection
Descent with Modification
• Organisms descended form a common
ancestor
• Organisms change with time, diverging form a
common form
• Cause evolution of a new species
Natural Selection
• Driving force for evolution
• During the struggle for resources, the
strongest survive and reproduce
• Fitness—ability to survive and reproduce
fertile offspring
• Those with the most advantageous
adaptations survive
• Adaptations—inherited characteristic that
increases an organisms chance for survival
Adaptations
• Can be physical or behavioral
Natural and Artificial Selection
• Abandoned the idea that species were perfect
and unchanging
• Significant variation in all species
• Farmers use variation in livestock and crops
• Selective breeding
Natural vs. Artificial
• Natural
– Differences among individuals of a species
• Artificial
– Selective breeding to enhance desired traits
among stock or crops
– Nature provides the variation among organisms
and humans selected those variations they found
useful