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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