AP Biology 2021 Free-Response Questions - College Board
2021
AP Biology
?
Free-Response Questions
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AP? BIOLOGY EQUATIONS AND FORMULAS
Statistical Analysis and Probability
Mean
x =
x = sample mean
Standard Deviation
n
1
xi
n?
i=1
s =
Standard Error of the Mean
s
SE x =
n
2
? (xi - x )
n -1
n = sample size
s = sample standard deviation (i.e., the sample-based
estimate of the standard deviation of the
population)
Chi-Square
?2 ?
?
? o ? e ?2
e
o = observed results
Chi-Square Table
e = expected results
Degrees of Freedom
p
value
1
2
0.05
0.01
3.84
6.63
5.99
9.21
3
4
5
6
7
8
7.81
11.34
9.49
13.28
11.07
15.09
12.59
16.81
14.07
18.48
15.51
20.09
? = sum of all
Degrees of freedom are equal to the number of
distinct possible outcomes minus one.
Metric Prefixes
Laws of Probability
If A and B are mutually exclusive, then:
P(A or B) = P(A) + P(B)
If A and B are independent, then:
P(A and B) = P(A)
? P(B)
Hardy-Weinberg Equations
p2 + 2pq + q2 = 1
p+q=1
p = frequency of allele 1 in a
population
q = frequency of allele 2 in a
population
Factor
Prefix
Symbol
10 9
10 6
10 3
10 ¨C 1
10 ¨C 2
10 ¨C 3
10 ¨C 6
10 ¨C 9
10 ¨C 12
giga
mega
kilo
deci
centi
milli
micro
nano
pico
G
M
k
d
c
m
¦Ì
n
p
Mode = value that occurs most frequently in a data set
Median = middle value that separates the greater and lesser halves of a data set
Mean = sum of all data points divided by number of data points
Range = value obtained by subtracting the smallest observation (sample minimum) from the greatest (sample maximum)
Rate and Growth
Water Potential ( Y )
Rate
dY = amount of change
dY
dt
dt = change in time
Population Growth
dN
= B-D
dt
(
dN
K-N
= rmax N
dt
K
YP = pressure potential
D = death rate
YS = solute potential
K = carrying capacity
rmax = maximum per capita
growth rate of population
dN
= rmax N
dt
Logistic Growth
B = birth rate
N = population size
Exponential Growth
Y = Y P + YS
The water potential will be equal to the
solute potential of a solution in an open
container because the pressure potential of
the solution in an open container is zero.
The Solute Potential of a Solution
)
YS = -iCRT
Simpson¡¯s Diversity Index
2
n
Diversity Index = 1 - ?
N
? ? total number of organisms of a particular species
( )
? ? total number of organisms of all species
i = ionization constant (1.0 for sucrose
because sucrose does not ionize in
water)
C = molar concentration
R = pressure constant
( R = 0.0831 liter bars/mole K)
T = temperature in Kelvin (?C + 273)
pH = ¨C log[H+]
Surface Area and Volume
Surface Area of a Sphere
SA ? 4? r
2
Surface Area of a Rectangular
Solid
SA ? 2lh ? 2lw ? 2wh
Surface Area of a Cylinder
SA ? 2? rh ? 2? r 2
Surface Area of a Cube
SA ? 6s 2
Volume of a Sphere
4
V ? ? r3
3
Volume of a Rectangular Solid
V ? lwh
r = radius
l = length
h = height
w = width
Volume of a Cylinder
V ? ? r 2h
s = length of one
side of a
cube
Volume of a Cube
SA = surface area
V ? s3
V = volume
AP? Biology 2021 Free-Response Questions
BIOLOGY
SECTION II
Time¡ª1 hour and 30 minutes
6 Questions
Directions: Questions 1 and 2 are long free-response questions that require about 25 minutes each to answer.
Questions 3 through 6 are short free-response questions that require about 10 minutes each to answer.
Read each question carefully and completely. Answers must be written out in paragraph form. Outlines, bulleted
lists, or diagrams alone are not acceptable.
You may plan your answers in this orange booklet, but no credit will be given for anything written in this booklet.
You will only earn credit for what you write in the separate Free Response booklet.
Question 1 is on the following page.
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AP? Biology 2021 Free-Response Questions
1. Polycystic kidney disease (PKD) is an inherited disease that causes water loss from the body and affects cell
division in the kidneys. Because water movement across cell membranes is related to ion movement, scientists
investigated the role of the Na+/K +ATPase (also known as the sodium/potassium pump) in this disease.
Ouabain, a steroid hormone, binds to the Na+/K +ATPase in plasma membranes. Individuals with PKD have a
genetic mutation that results in an increased binding of ouabain to the Na+/K +ATPase . The scientists treated
normal human kidney (NHK ) cells and PKD cells with increasing concentrations of ouabain and measured the
number of cells (Figure 1) and the activity of the Na+ / K +ATPase (Figure 2) after a period of time. The
scientists hypothesized that a signal transduction pathway that includes the protein kinases MEK and ERK
(Figure 3) may play a role in PKD symptoms.
Figure 1. Cell number compared with the number of
cells at 0 pM ouabain. Normal human kidney (NHK )
Figure 2. Percent Na+/K +ATPase activity of NHK and
cells and polycystic kidney disease (PKD) cells were
PKD cells treated with increasing concentrations of
treated with increasing concentrations of ouabain. Error ouabain. Error bars represent ¡À2SE x .
bars represent ¡À2SE x .
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