Change and Evolution

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Change and Evolution
lions have to be able to catch their prey in
order to eat if a lion has a mutation that make
s it slow, will it be able to catch it's prey?
if a lion has a mutation to make it faster,
will it be able to catch it's prey?
a lion that can catch its prey better will ea
t more and therefore more likely to live
when there isn't enough food for all
natural selection organisms that are better s
uited to their environment tend to survive bet
ter and reproduce more often
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Change and Evolution
Darwin found many different types of finches in
the Galopagos Islands all are related (some mor
e than others) but each are specialized for a
very specific environment
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Change and Evolution
On the Origin of Species, published in 1859,
described a theory that would explain why the
finches are similar yet different (among many
other examples) and has been very thoroughly
studied natural selection will allow some mutan
ts (and everyone has mutated genes!) have a su
rvival advantage compared to others (ie. better
hearing, more efficient metabolism, stronger
muscles, etc) organisms that can survive better
are able to pass on their genes
Descent with modification idea that, over time,
the majority of individuals in a population h
ave the 'mutation' that gives them a
survival advantage-- requires many generations
to become common evolution populations change
over time to fit their environment
individual changes occur RANDOMLY- a few are
good, most are bad
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Change and Evolution
we can see the process of selection in everyday
life selective breeding allows breeders to embe
d traits in a species artificial selection con
trolled, directed breeding for a particular
trait orchids, dogs, cats, cows, wheat, many ma
ny others have been bred
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Change and Evolution
selection can also occur due to changed
environmental conditions moths in england used
to be brown, with brown barked trees
during the industrial revolution, pollution ligh
tened the bark and moths became mostly white a
s the environment got cleaned up, bark went ba
ck to brown as did moth color camoflage is im
portant for their survival ones which match s
urvive
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Change and Evolution
fossils provide a snapshot of what organisms
looked like long ago fossils occur when mineral
-rich water gets into organic material and the
water slowly evaporates- must be the same age
as the rocks around them
fossil record ordered array of fossils and
surrounding rock strata layers of rock that are
all the same age
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Change and Evolution
some fossils are similar to current organisms
others are very different
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Change and Evolution
internal anatomy of organisms are related to each
other, even if their current form and function
are very different from each other
even wings of birds and bats look similar to
human arms and seal flippers bird bones are muc
h lighter and hollow compared to seals or huma
ns bats' digits spread out a lot to increase th
e surface area of the wing seal flippers an
d bat wings have webbing between their digits
humans don't
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Change and Evolution
embryos of different organisms look alike
more closely related organisms look alike later
in their development Known as Von Baer's laws,
and were developed before Darwin and
evolution does NOT say that adult organisms m
ust look alike to be related
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Change and Evolution
DNA evidence also suggests that all organisms are
related to one another DNA is more similar betw
een closely related organisms than distant ones
genes with the same function are more similar be
tween organisms than similar genes within the
same organism cladistics process of showing th
e relatedness of 2 organisms using DNA and morph
ology
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Change and Evolution
evolution occurs at the level of populations,
NOT individuals population group of organisms
of one species in a location in terms of evolut
ion, individuals are expendable-- not every
organism born is going to survive it is onl
y the organisms that have offspring which count
toward the next generation organisms that s
urvive better are going to have more offspring
survive gene pool complete collection of all a
lleles of all genes in a population
includes all mutations as well as common
differences (ie. blood type)
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Change and Evolution
genes get passed on to the next generation only
if an organism survives can be determined using
a method similar to a Punnett square
imagine a gene that controls some trait such as
round vs wrinkled peas round vs wrinkled does
not affect survival-- both are just as fertile
secondly, imagine that one allele (form) is
more common than the other wrinked r (i
e. recessive) occurs 70 of the time and round R
30 R(0.3) r(0.7) R(0.3) RR(0.09) Rr(0.2
1) r (0.7) Rr(0.21) rr(0.49) true breeding r
ound RR 0.30.3 0.32 0.09
true breeding wrinkled rr 0.7 0.7 0.72
0.49 heterozygotes Rr rR 0.30.7 0.70.3
0.21 0.21 0.42 these 3 types count all possi
bile individuals 0.09 0.49 0.42 1.00
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Change and Evolution
Hardy-Weinberg equation formula for calculating
offspring ratios p2 2pq q2 1 p and q ar
e the ratios of any 2 alleles if there isn't a
ny selection, offspring ratios don't change over
time! R(0.3) r(0.7) R(0.3) RR(0.09) Rr(0
.21) r (0.7) Rr(0.21) rr(0.49) if one trait
(say rr) reduces the survival chance of the
individual, then fewer of those individuals wi
ll appear in the next generation because
there are fewer r alleles (perhaps .68 instead
of .70, then R must go up to .32 so that all a
lleles are counted) this formula tells how trai
ts get inherited in a population AND how
some offspring surviving better changes the
ratios in the next generation
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Change and Evolution
Hardy-Weinberg makes a number of assumptions that
make the math easier, even though we know that
they aren't true 1) the population must be lar
ge for Hardy-Weinberg to be true
genetic drift random change of a gene over time
is more common and significant in a small popul
ation endangered species, because they have
a small population, can have a lot of
genetic drift genetic diversity variation fo
und in a population-- always smaller in a s
mall population than a large one
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Change and Evolution
2) there is no gene flow or migration into/out of
a population gene flow movement of new or diff
erent genes into a population if individuals fr
om a different population join one group, it can
change the ratios 3) mutations do not al
ter the gene pool mutations, or changes in the
DNA do occur but are rare it takes many generat
ions for a new mutation to become a common one
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Change and Evolution
4) mating must be random for Hardy-Weinberg to be
true if RR individuals prefer RR individuals, t
hat will make it non-random non-random will ch
ange gene frequencies related issue to 5
5) natural selection does not occur
if some genes are selected against, ratios have
to change same thing happens if mating isn't ra
ndom Hardy-Weinberg is a simple way to understa
nd inheritance in a population
the math gets MUCH harder with natural
selection, migration, etc
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Change and Evolution
natural selection can work in 3 different ways
stabilizing selection gets rid of extremes
perhaps the smallest and the largest
directional selection gets rid of one extreme
get rid of the largest, the average is
smaller disruptive selection gets rid of the a
verage some are smaller, others are larger
because selection works on a population, over ti
me the loss of individual organisms cause the
population 'norm' to change