Download CH. 23 (A): EVOLUTION of

AP BIOLOGY
NAME:____________________________________
DATE:__________________________PER:______
CH. 23 (A): EVOLUTION of _________________
[combining the work of ____________ with _____________!]
 Recall, EVOLUTION does not act on ________________, but ______________
_______________ DOES ACT on ________________!
 SO, as natural selection acts on individuals, those with adaptations
__________ for their environment or environmental changes, will survive &
________________, therefore affecting the ALLELES present in the ________
_________ of a particular __________________!
 MACROEVOLUTION: the larger level at which we can study _______________
change on a __________ level of a whole ___________.
 MICROEVOLUTION: the smallest level at which we can study
_____________________ change.

As _____________ in the genetic makeup of a __________________ occurs from
__________________ to ________________.
 What makes EVOLUTION possible?  ________________________
 Caused through:
 _________________
 SEXUAL RECOMBINATION (
o produces the variation in ___________ ___________ that contributes to the
individual heritable differences in a ___________________.
 GEOGRAPHIC VARIATION: a type of _______________ _________________
(between ___________________) when organisms of the same __________ exhibit
_____________/______________ especially when separated into different &
separate _________________.
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 MUTATIONS: originate from changes in the _________________ sequence of
_________, resulting in _________ genes & _________ alleles.
o can have a significant impact on _________________.

"POINT MUTATION": a change of as little as ____ base in a gene.

MUTATION RATES:
o Mutation rates tend to be ________ in plants & animals.
o But __________, especially those with RNA, have much higher
mutation rates.
 Can result in drug-resistant __________, like HIV.
 SEXUAL RECOMBINATION: (as a result of sexual ___________________)
o almost all _________________ variations based on genetic differences result
from ___________________ shuffling of the existing alleles in a ___________
___________.

Ex: _______________ & ____________ have high _______________ rates
& extensive _________________.
 produces _________________ that make adaptation possible...
 ...BUT, does NOT create new alleles/genes & doesn't change their frequency,
ONLY "re-shuffles" the alleles in the _________ _________ of a population.
 Recall, individual organisms DO ______ EVOLVE!!!...but ___________ DO!!!
o Although, _____________ ______________ does act on individuals, because each
individual's ___________ affect it’s ______________ & reproductive success
compared to other individuals...
o ...BUT, the EVOLUTIONARY IMPACT of natural selection is ONLY apparent in
the changes in a POPULATION (____________) of organisms over __________!
o EX: Cuban tree snails (Fig.23.1)

They have _______________ ________________ (__________________ among
individuals within a _____________) as a result of genetic differences....

....suppose they live in an environment of red grasses...causing snails
with more _______ colored patterns (better camouflaged against their
surroundings = “more ______”) to be _________ likely to survive, THUS, the
proportion of snails with that color pattern will tend to ______________
from one _________________ to the next...
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
...BUT, _________________ CANNOT evolve themselves to survive (snails
cant "decide" to change their patterns to the more red-color)...

...THUS, the ________________/____________, NOT its _______________
members, EVOLVES over time, as some traits become _________ common
within the population, and others become _________ common.
 POPULATION GENETICS:

Studies the _________________ changes in _________________ over ___________.
o Individuals in a population must have _______________ ________________ in order
for _________________ to occur (via _________________ ________________), BUT, does
the presence of genetic variation, guarantee evolution will occur???
 _________...WHY? ______________________________________________________
 POPULATION: a localized group of _________________ that are capable of
___________-_______________ & producing ____________/____________ offspring
= same ____________, same ___________, & can ________________ & produce
_____________ offspring! [see Fig.23.3]
o The same ___________ can have different ________________ because they are
________________ from each other, thus rarely exchange
__________/______________ by breeding.
 GENE POOL: a population’s genetic ______________.

the "pool" of available genes/_____________ present within a population (in an
__________) at any one time; consists of all the possible, available
____________/traits.
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 ALLELE FREQUENCY: the frequency/proportion/”__________________” of certain
alleles within a specific ___________________.

The frequency of specific alleles can vary within different _________________.

For example: Cuban snails…
o In red-grass areas, the alleles for ________-patterns are found at
_______________ frequencies/__________ common within that particular
___________________, while the alleles for other patterns are found at
_______________ frequencies/__________ common within that particular
___________________.
o In green-grass areas, the alleles for ____________-patterns are found at
_______________ frequencies/__________ common within that particular
___________________, while the alleles for other patterns are found at
_______________ frequencies/__________ common within that particular
___________________.
 The events & trends that occur within _________________ GENETICS, leads to
___________________ of a species as a whole, over ___________...SO, to study &
understand EVOLUTION, you have to study-understand __________________
_________________!
 The HARDY-WEINBERG PRINCIPLE:
o Recall, we answered the question, “does the presence of genetic variation,
guarantee evolution will occur?” _______!
o One way to assess IF natural selection or other factors are causing evolution at a
particular LOCUS, is to determine what the genetic makeup of a _________________
would be if it were ________ evolving at that ___________...THEN, we COMPARE
that to a real ________________, & if there are _______ differences, then we can
conclude that the real population is NOT ____________...however, if there ARE
differences, then the real population IS ______________, & we can try to figure out
what are the causes…
 WHY are we looking at a particular LOCUS???
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
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
The HARDY-WEINBERG THEOREM:
(RE-READ section in bk!)
o Describes a ______________ whose __________ ___________ is NOT ____________.
o the principle that states that the frequencies of ____________ and genotypes in a
population (___________ ___________) remains ______________ from generation to
generation, provided that only Mendelian segregation (including random
fertilization) and recombination of alleles are at work…such a gene pool is said to
be in _______________________________________________.

The HARDY-WEINBERG EQUILIBRIUM:
(RE-READ section!)
o the condition describing a non-______________ _________________; population is in
______________ _________________.
 Instead of thinking about what possible genetic combinations can result from only
____ cross (____________ ____________), we must now consider _______ the possible
genetic ________________ that can result within an entire ________________!
 SEE Fig.23.6 AND 23.7
 If a population is in Hardy-Weinberg equilibrium & its members mate randomly
generation after generation, alleles & genotype frequencies would remain
______________.
 The system operates somewhat like a deck of cards: no matter how many times
you shuffle the deck and deal out hands/or pairs (alleles). The cards in the
amount and types of cards in the deck remains the __________ (_________
___________; allele frequency); aces won’t magically change into another card.
 In the same way, the “shuffling” of a population’s _________ __________ over the
generations cannot, in itself, ___________ the frequency of alleles present in the
gene pool.
 The HARDY-WEINBERG THEOREM is used to statistically ____________ allele
frequency of certain __________ within a specific ________________.
 CONDITIONS for Hardy-Weinberg Equilibrium:
o the Hardy-Weinberg theorem describes a _________________ population that is
_______ evolving…
o …BUT, in real populations, allele and genotype frequencies ______ change over
time…
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o …this is because the 5 conditions required for non-evolving populations
(i.e.___________-______________ _________________) are ___________ met for long in
nature:
1) Extremely large population size. The smaller the population, the greater the
role played by chance fluctuations in allele frequencies from one generation
to the next, known as _____________ __________.
2) No gene flow. Gene flow, the transfer of alleles between _______________ can
alter allele frequencies.
3) No mutations. By introducing or removing genes from chromosomes or by
changing one allele into another, ________________ modify the __________
___________.
4) Random mating/random fertilization. If individuals preferentially choose
__________ with certain genotypes, including close relatives (inbreeding),
random mixing of gametes does not occur.
5) No natural selection. Differential survival and _______________ success of
individuals carrying different genotypes will alter ____________ frequencies.
 in order for a population to be in Hardy-Weinberg equilibrium, these 5
conditions must be met, which is _______ likely in nature…
 …SO, IF these 5 conditions are NOT met, which is ___________, then
__________________ occurs!!!
 Though natural populations rarely if ever are in true Hardy-Weinberg
________________, the rate of evolutionary change in many populations is so
__________ that these populations ____________ to be close to equilibrium. This
enables us to obtain approximate estimates of ____________ & _______________
frequencies.
 Recall, natural populations rarely, if ever, are in true Hardy-Weinberg
________________...but because evolutionary change occurs so slow, populations
can appear to be close to equilibrium…
 thus, the H-W-theorem & equation enables us to obtain approximate estimates
of ____________ & _______________ frequencies.
o SEE “Population Genetics & Human Health” section as an example
 APPLICATION: the H-W equation can be used to ________________ the % of
the population carrying an _____________ for an inherited disease.
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 GENETIC DRIFT: unpredictable fluctuations in allele ________________ from 1
generation to the next because a population is finite in size (not infinite).
~ SEE FIGURES in BOOK!!!
o can result in loss of alleles by ____________.
o over time, drift tends to ____________ genetic variation through losses of alleles
from the ___________ ___________
o 2 situations can increase the likelihood that genetic drift will have a large
impact on a population: bottleneck effect & founder effect

BOTTLENECK EFFECT: a type of genetic drift that results from a sudden
change in the environment, i.e. a ____________ ______________ or even
____________ ____________, like a flood or fire...that reduces the size of a
_________________, and the surviving population's __________ __________ may
not be reflective of the original population's gene pool.
o by chance, some alleles may be more common among the survivors,
while others are less common or even eliminated altogether.
o SEE FIGURES in BOOK!!!

FOUNDER EFFECT: a type of genetic drift that occurs when a few
individuals become isolated from a larger population (i.e. island formation),
with the result that the new population's gene pool is not reflective of the
original population.
 A Summary of the EFFECTS of GENETIC DRIFT:
1) ________________________________________________________________________
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________________________________________________________________________
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2) ________________________________________________________________________
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________________________________________________________________________
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3) ________________________________________________________________________
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4) ________________________________________________________________________
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 GENE FLOW: genetic additions to or subtractions from a population resulting
from the _______________ of fertile individuals or gametes.
o tends to reduce the ________________ between populations.
 the 3 major factors that can alter allele frequencies & cause
the most evolutionary change are ______________
_______________, GENETIC DRIFT, & GENE FLOW.
 RE-READ "A Closer Look at Natural Selection" + "Evolutionary Fitness" or
"Relative Fitness"
 RE-READ "The Key Role of Natural Selection in Adaptive Evolution!!!
 RE-READ “Case Study: Impact of Genetic Drift on the Greater Prairie
Chicken”
 RE-READ “Sexual Selection”
 RE-READ “Why Natural Selection Cannot Fashion PERFECT ORGANISMS”
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