Transcript Macroevolution/HW 5/2/14

Macroevolution &
Hardy Weinberg
Equilibrium
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Mr. Joey Norman
BGHS 5/3/2014
May 12, 2014
Multiple-Choice Strategies
* Don't be afraid to write in the test book. When you take the exam,
you will be given a test book and a Scantron® answer sheet on which
you will bubble in your answers. No one is going to look at the test
book itself -- only your answers on the answer sheet will be scored.
Therefore, feel free to write all over your test book (but keep the
answer sheet neat). Circle the questions in the book that you skip so
you can easily find them again ... cross out the letters of choices that
are definitely wrong ... mark up graphs ... write whatever it takes in
the book to get the right answer.
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* Don't think too hard. There are easy questions and there are hard
questions. Don't let the easy questions mislead you. If you come across
what seems like an easy question, it probably is. Don't suspect
everything to be a trick question.
May 12, 2014
Multiple-Choice Strategies
* Pace yourself. Don't spend too much time on any problem. You have 90
minutes to answer 63 multiple choice questions & 6 grid-in, quantitative
questions -- that leaves you about 45 seconds per question. If you come across
a question you can't answer, mark it so you can easily come back to it later. If
you can eliminate some answer choices right off, mark those too. The
questions on the exam are NOT arranged from easy to hard, so you don't
want to waste time mulling over hard questions and not try all the questions
on the test. Why spend so much time answering a hard question when you
can answer three easy ones and get three times the points in the same amount
of time? The test is designed so that the average person earns a score of 50%,
so it is recommended to guess and not to leave any question blank.
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Watch for key phrases like "all of the following EXCEPT" and "NOT" in the
questions. The College Board loves questions with these words in them. By
adding these words, the test writers force you to go through each answer
choice and determine whether or not it is true or false. Normally, a multiplechoice question will ask you to pick out the correct answer (true statement).
When the phrases "EXCEPT" and "NOT" are used, however, you must pick
out the incorrect answer (false statement). To avoid confusing themselves,
many students find it useful to mark true statements with a "T" in their test
book and false statements with an "F."
May 12, 2014
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Free-Response Strategies
* 90 minutes – 2 long FRQ’s & 6 short FRQ’s
Write your strongest answer first.
Unload all the information in your brain.
Answer all parts of the question.
Don't do more than is required.
Answer each part of the question separately.
Try every question.
Don't be afraid to guess.
ATFQ
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Macroevolution
I. Mutations
The only source of NEW genes & NEW
alleles
Only mutations in cell lines that produce
gametes can be passed on to offspring
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Types of Mutations
A) Point Mutation
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Change in one base in a gene
Can impact phenotype
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Sickle cell anemia
Types of Mutations
B) Chromosomal Mutation
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Delete, disrupt, duplicate, or rearrange
many loci at once
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Most are harmful, but not always
II. Gene Flow
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Population loses or gains alleles by genetic
additions or subtractions
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Results from movement of fertile
individuals or gametes
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Reduces the genetic differences between
populations, makes populations more
similar
III. Genetic Drift
Unpredictable fluctuation in frequencies
from one generation to the next
The smaller the population, the greater
chance
Random & nonadaptive
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III. Genetic Drift
A) Founder effect = individuals are
isolated and establish a new population
– gene pool is not reflective of the source
population
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III. Genetic Drift
B) Bottleneck effect = a sudden change in
the environment reduces population size
– survivors have a gene pool that no
longer reflects original
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III. Genetic Drift
1.
2.
3.
4.
Genetic drift is significant in small
populations
Genetic drift causes allele frequencies
to change at random
Genetic drift can lead to a loss of
genetic variation within populations
Genetic drift can cause harmful alleles
to become fixed
IV. Natural Selection
Alleles are passed to the next generation
in proportions different from their
frequencies to the present generation
Those that are better suited produce
more offspring than those that are not
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IV. Natural Selection
Natural selection acts more directly on
the phenotype and indirectly on the
genotype
Can alter the frequency distribution of
heritable traits in 3 ways:
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1) Directional selection
2) Disruptive selection
3) Stabilizing selection
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IV. Natural Selection
1) Directional selection
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Individuals with one extreme of a phenotypic
range are favored, shifting the curve toward this
extreme
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Example: Large black bears survived periods of extreme
cold better than small ones, so they became more
common during glacial periods
IV. Natural Selection
2) Disruptive Selection
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Occurs when conditions favor individuals on both
extremes of a phenotypic range rather than
individuals with intermediate phenotypes
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Example: A population has individuals with either
large beaks or small beaks, but few with intermediate –
apparently the intermediate beak size is not efficient in
cracking either the large or small seeds that are
available
IV. Natural Selection
Stabilizing Selection
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Acts against both extreme phenotypes and favors
intermediate variations
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Example: Birth weights of most humans lie in a narrow
range, as those babies who are very large or very small
have higher mortality rates
IV. Natural Selection
Why Natural Selection cannot produce
perfect organisms:
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1) Selection can only edit existing variations
 2) Evolution is limited by historical constraints
 3) Adaptations are often compromises
 4) Chance, natural selection, & the environment
interact
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Hardy-Weinberg
Hardy-Weinberg Equilibrium
Used to test whether a population is
evolving
Used to describe a population that is
NOT evolving
Frequencies of alleles & genes in a gene
pool will remain constant over
generations
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5 Conditions for
Hardy-Weinberg
1) No mutations
2) Random mating
3) No natural selection
4) The population size must be large
(no genetic drift)
5) No gene flow (Emigration,
immigration, transfer of pollen, etc.)
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Hardy-Weinberg Equilibrium
p2 + 2pq + q2
 p = dominant allele
 p2 = homozygous dominant (BB)
 q = recessive allele
2
 q = homozygous recessive (bb)
 2pq = heterozygous (Bb)
Hardy-Weinberg Equilibrium
Example:
Hardy-Weinberg Equilibrium
Example:
90% = B (p) = 0.90
10% = b (q) = 0.10
What percentage is Bb?
p2 + 2pq + q2
p2? pq? q2?
2pq = 2(0.90)(0.10) = .18 or 18% Bb
Hardy-Weinberg Equilibrium
Examples:
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Hardy-Weinberg Equilibrium
Examples:
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Hardy-Weinberg Equilibrium
Examples:
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