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EVOLUTION
“It is not the strongest of the species
that survives, nor the most intelligent
that survives. It is the one that is the
most adaptable to change.”
~Charles Darwin
EVOLUTION
Change in a species’ genetic makeup over time
Theory
(well tested explanation)
Charles Darwin
BEFORE DARWIN…
Inheritance of Acquired Traits
(Jean Baptiste Lamarck)
Organisms acquired or lost traits based on use
during its lifetime & passed to offspring
BEAGLE (1831)
Collected specimens & fossils around
the world
GALAPAGOS ISLANDS
•
Observed many organisms
•
•
High number of endemic species (species found only there)
97% of island is protected
GALAPAGOS ISLAND SPECIES OF INTEREST
1859 – ORIGIN OF SPECIES
Before
DNA
Introduced
 Artificial
selection
 Natural selection
 Evolution
ARTIFICIAL SELECTION
Nature provides variation, humans select variations
that are useful.
Examples:
• Farmers breeding best livestock
• Domesticated dogs
NATURAL SELECTION
The traits that help an organism survive
in a particular environment are
“selected” for in nature
STEPS IN NATURAL SELECTION
1. Genetic variation
 Difference
in color, size, etc.
 Genetic mutation (after Darwin)
2. Over
3.
population
Struggle to survive
 Not
4.
enough resources
Successful reproduction
 Well
adapted live and reproduce
Adaptation Video
EUROPEAN PEPPERED MOTHS
•
•
•
Rested on tree trunks
Moths rest with their wings folded down
Birds were predators
EUROPEAN PEPPERED MOTHS
Two
color variations
 Dark
 Pale
Before
 Pale
By
1850
more common
1860
 Dark
more common
WHAT HAPPENED IN THE
1850S?
Trees
covered in
lichens
 Pale: blended
 Dark: stood out
1850s – Industry
Soot covered trees
 Dark: blended
 Pale: stood out
 Simulation
NATURAL SELECTION TO
EVOLUTION
• Insecticides
– chemicals
used to rid plants of
unwanted insects
• Antibiotics – treat
bacterial infections
• Work well before = now
ineffective
 Why?
 Resistance
SUMMARY OF DARWIN’S THEORY
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than
survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass
those advantages to their children
5. Species alive today are descended with
modifications from common ancestors
TWO TYPES OF EVOLUTION
1. Divergent – related species become more dissimilar
2. Convergent – unrelated species become more
similar in appearance as they adapt to a similar
environment
EVIDENCE OF EVOLUTION
 Fossil
Record
Homologous
structures
DNA
Embryonic structures
FOSSIL RECORD
Fossils changed between different
layers of the earth
Youngest
Oldest
HOMOLOGOUS STRUCTURES
Structures with different mature forms that
develop from the same embryonic tissue
Modified for specific function
ANALOGOUS STRUCTURES
Similar form & function, but are structurally
quite different
Same habitat
DNA
Common ancestors =common DNA
Greater # of DNA similarities =
closely related
EMBRYONIC STRUCTURES
Embryos
may
look more
similar to
adults
All vertebrates
look similar as
embryos
VESTIGIAL STRUCTURES
Remnants of once useful structures
Ex. – Whale
Ex. – Humans
 Hind limb bones
• Goosebumps
Speciation
Geographic Isolation
Changes leading to formation of new
species.
Populations evolve and become
reproductively isolated from
each other(members of two
populations cannot interbreed)
 Behavioral
isolation