Download Trends in Evolution

STARTER #48 AND OBJECTIVES
Table of Content: Trends in
Evolution
Starter: Comparing homologous
structures of lizzard’s and cat’s
forelimb we saw similar set of bones.
Why is that?
Objectives:
 Analyze and evaluate the evidence for
evolution
HOMEWORK AND REMINDER
Homework:
Evolution concept map
Reminder:
Cell phone should be off and out of
sight!
ID and Dress code check
EVOLUTION- - HOW DID CHANGE OCCUR?
Process by which modern organisms
have descended from ancient organisms
Long, slow process of change
Any change in the frequency of genes
affects the gene pool
Variations exist within species
Change in population over time
GENE DUPLICATION
New genes can
evolve through
duplication, followed
by modification, of
existing genes.
MOLECULAR CLOCKS
Molecular clocks use mutation rates to
estimate the time that two species have
been evolving.
MUTATIONS
More differences between DNA sequences of
two species indicates more time elapsed since
they shared an ancestor.
HOX GENES AND EVOLUTION
Small changes in Hox
gene activity during
embryological
development can
produce large
changes in adult
animals.
SPECIATION DUE TO ISOLATION
Speciation is the
process of forming
new species and can
occur in several ways:
Abert’s Squirrel
1. Geographic
barriers (mt.
ranges, ocean)
Kaibab Squirrel
SPECIATION DUE TO ISOLATION
2. Temporal changes = timing
(flowers, honeybees)
SPECIATION DUE TO ISOLATION
3. BEHAVIORAL ISOLATION
SUMMARY
Isolated gene pools diverge into separate species.
Reproductive isolation occurs.
Members of a species share a gene pool.
Patterns of evolution
ARTIFICIAL SELECTION
 Artificial Selection is the process of when people
(instead of nature) select which organisms get to
reproduce, to get their favorable desire traits.
DIVERGENT EVOLUTION
 On species give rise to many species
which means organisms have a
common ancestor
 Changes in environment cause them
to adapt
 Overtime, they become less and less
alike and behave differently, but they
are still related!
 Also known as: Adaptive Radiation
ADAPTIVE RADIATION
DIVERGENT EVOLUTION
CONVERGENT EVOLUTION
Unrelated organisms develop similar
characteristics due to environmental pressures
May look or act the same, but not related at all!
Don’t have common ancestor
Shark - dolphin
Bat – bird - butterfly
CONVERGENT EVOLUTION
COEVOLUTION
Two organisms
evolve together in
response to
changes in each
other over time
Insects & flowers
Both species become dependent
on each other for survival
TIMING OF EVOLUTION
GRADUALISM
Change is SLOW, constant, and predictable
due to environment
EX: Leg changes in horse population
PUNCTUATED EQUILIBRIUM
Descent punctuated
by short period of
stable follow by a
rapid change
associated with
environmental
changes
Ice age, meteorite
impact, volcanoes
HARDY-WEINBERG PRINCIPLE
 If the following 5 conditions are not met, then
evolution cannot occur because there won’t be any
changes:
1. Immigration or migration
2. Large Populations
3. Random mating, no preference
4. Natural selection
5. Mutations occur
 However, these conditions do exist and happen in nature,
Therefore…populations do change or evolve over time!
NATURAL SELECTION CAUSES
GENETIC DRIFT
A random change
in allele frequency
in a population
Greater effect on
small populations
Can cause an
allele to become
common in a
population
GENETIC DRIFT IS THE CHANGE IN THE ALLELE FREQUENCY IN A
P O P U L AT I O N D U E T O R A N D O M S A M P L I N G O F O R G A N I S M S
T H E F O U N D E R E F F E C T I S L O S S O F G E N E T I C VA R I AT I O N W H E N N E W
P O P U L AT I O N I S E S TA B L I S H E D F R O M L A R G E R O N E
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Shows how two
small groups from
a large diverse
population could
produce new
populations that
differ from the
original group
TYPES OF GENETIC DRIFT
1. Directional Selection:
Individuals at one end
of the phenotypic
spectrum have the
highest fitness
TYPES OF GENETIC DRIFT
2. Disruptive selection:
Cause a population to
diverge
May cause speciation
TYPES OF GENETIC DRIFT
3. Stabilizing Selection:
Causes the population
to become more
average in phenotype
FOSSILS IN SEDIMENTARY ROCK
1
2
Water carries small rock
particles to lakes and seas.
3
Dead organisms are buried
by layers of sediment.
The preserved remains
may later be discovered
and studied.
WHAT CAN FOSSILS REVEAL?
RELATIVE DATING
RADIOMETRIC DATING
PLATE TECTONICS AND EVOLUTION
End of the Permian Period
End of the Cretaceous Period
Triassic Period
Present Day
MICROEVOLUTION
MICROEVOLUTION
MICROEVOLUTION
MACROEVOLUTION
PATTERNS OF EXTINCTION