Transcript evolution - TeacherWeb

EVOLUTION
Change in a
species through
time
How Do Living Things Change
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Variation
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______________________
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_______________________
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During DNA replication
During transcription/ translation
Getting different traits from 2 parents versus 1.
CAN YOU CHANGE YOUR DNA (like right now,
with no super secret laser)?
How did life START on Earth?
Evolution does not explain creation of life
just that life changes…so how did life
start?
 Several hypothesis’
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Creationism
Extra-terrestrialism
Heterotroph hypothesis
Heterotroph hypothesis
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Life began about 3.5 million years ago
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At that time there was no oxygen, just a
mixture of hydrogen, water, ammonia, and
methane…with a flash of lightning, the first
living organism was formed. It was an
_______________________.
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Still no oxygen, a __________ formed
_________________ AUTOTROPH –
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Since we know that autotrophs make
Oxygen, a mutation that would allow an
organism to utilize that oxygen would be
beneficial
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Along came ____________ organisms
Evidence for Evolution
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How do we know organisms lived long ago (like
millions of years ago) and how do we know what
they looked like?
Inorganic Evidence
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______________
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Sedimentary rock
Carbon Dating
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More evidence for evolution
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Organic evidence
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_______________–
same structure different
function
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_______________ =
different structures
same function
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_______________–
organs that no longer
have a function (like an
appendix)
Pelvis of
a whale
Organic Evidence
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Comparative _______________ – comparing the
developing fetus’ of several species
Comparative _______________ – comparing the
tissues of several species
Comparative _______________ – comparing
DNA, proteins, etc, of several species
Theories of Evolution
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Lamark – First to try to account for
making sense of why things look similar…
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Theory of need
Theory of use and disuse
Inheritance of Acquired Characteristics
Weismann – “The mice man”
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Disproved Lamark
Darwin
Father of evolution – 1809 - 1882 went to
school to be a doctor. Hated it! Went to
school to become a priest. Went on the ship
the HMS Beagle in 1831 to the Galapagos
Islands. Collected data from around the
Islands and wanted to make sense of how
they looked so similar to the main land
animals but yet so different.
 In 1859 published his theory of Natural
Selection
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Natural Selection
The finches were one of
the main species that he
looked at and noticed
these differences.
 There are 5 parts to his
theory of evolution:
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1. _______________ – (like
seen here) – differences
within a population
Parts to evolution
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2. _______________ – making more babies
then can survive.
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3. _______________ – Because there are too
many offspring, they must fight for survival.
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4. _______________– With the competition
and variation within the species, those with
favorable adaptations will survive!
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5. _______________ - Those that best survive
will pass on those traits to their offspring
Types of natural selection
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_______________– eliminates extreme
individuals (rather then tall or short plants
you get medium plants)
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_______________– selection against one
extreme – widow bird selecting for long
tails
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_______________– eliminates
intermediate individuals - tall and short
dandelions
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PLEASE NOTE – THE ENVIRONMENT IS
THE SELECTING AGENT!!!!!!
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If the organisms/ species has the GENE
then it will survive.
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If the environment CHANGES – the traits
favored also CHANGES
Genetic Basis for Evolution
Darwin didn’t know about DNA – first
came Mendel to explain genetics
(genotype and phenotype) then Watson
and Crick in the 1950’s with DNA…
 With Mendel we could explain why the
frequency of the alleles for certain traits
increase within a gene pool while others
decreased.
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Hardy Weinberg Equilibrium
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A large sexually reproducing population
will have a stable allelic frequency given
the following five conditions
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Large population
No immigration or emigration
Random mating
Random reproductive success
No mutation
Hardy Weinberg equation
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Please see your notes from Genetics –
(population genetics) for equation
Remember we used a punnett square to
determine frequencies.
WHY would this equation help in evolution?
Evolution by chance
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Genetic Drift – evolution in the absence of
natural selection
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______________ population size is drastically
reduced by some event. For example, you
have 50 pennies and 50 nickels in your pocket,
you lose ALL BUT 4, you could have any
combination of pennies and nickels…
______________ – a small number of
individuals populate a new area
_______________ – must occur in a gamete to
be passed on – to dramatically effect a gene
pool must be combined with one of the above
Isolation
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A physical separation of one population from
another so that interbreeding can not occur
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Geographic Isolation – physical barriers like mountains/
oceans
Physiological barriers –
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Premating – differences in species recognition/ mating calls
etc
Post mating – differences in genetalia, sperm can’t fuse
with ovum, young may survive but are sterile (mule)
Pace of evolution
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___________ –
over time,
accumulations of
small differences
makes two
population into two
different species
_________
__________ – long
period of no change
followed by a quick
dramatic change
Evolutionary/ phylogenetic trees
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These allow us to see common ancestors
and evolutionary relationships **Based
on DNA