AP Test - Biology

4 Big Ideas

Collegeboard has broken down the entire AP Biology Course into 4 Big Ideas: Evolution, Cellular Processes, Genetics and Information Transfer, and Interactions. These 4 Big Ideas are further broken down into Learning Objectives, Essential Knowledge, and Enduring Understanding. Learn Objectives are what the students need to be able to do. Essential Knowledge is what the students need to know. Enduring Understanding is concepts to understand. For the full list of them, visit https://secure-media.collegeboard.org/ap-student/course/ap-biology-2012-course-exam-description.pdf.

Section
Type
# of Qs
% of Final Score
Timing
1
Part A: Multiple Choice
Part B: Grid In
63
6
50%
90 minutes
2
Long Free Response
Short Free Response
2
6
25%
25%
80 minutes + 10 minute reading period

The AP Biology exam is three hours long and includes two 90-minute parts: a multiple-choice/grid-in section and a free-response section. Each section accounts for half of the student’s exam grade.

Section 1 consists of 63 multiple-choice and 6 grid-in questions. The grid-in questions are introduced as part of the changes made in 2013. This will increase the need for knowing applications of mathematical concepts rather than rote memorization. The questions test 7 Scientific Practices (big ideas) and 55 Essential Knowledge (content, details). Each question is drawn from a coordinate shown below. This change to the exam shows a growing need for reasoning skills and an inquiry-based learning of essential concepts rather than simple factual recall.

 
Essential Knowledge (55)
 
Q31
Q32
 
Q3
Q50
 
Q1
Q22
Q43
 
Q9
Q35
 
Q2
Q17
Q12
Q28
Q4
 
Q19
Science Practice (7)
Q5
Q8
Q19

Remember to allocate your time carefully, because the grid-ins will take more time to complete. To aim for a 5, spend about 45 to 50 seconds per question and answer 60 or more questions correctly. Note that since the changes in May 2013, there are now 4 instead of 5 answer choices for the multiple-choice questions. This change saves students’ valuable time without altering the rigor of the exam in any way. Points are not deducted for incorrect or unanswered questions.

The first 10 minutes of section 2 is the obligatory reading period; this is extremely valuable, so students should jot down notes and have a plan of attack ready for each question. In the past, pre-2013, there were 4 long essays. It now consists of 2 long-free response essays and 6 short-free response essays, each type with equal weight. In the long free response, each question (20-25 minutes) is scored on a 0-10 point scale even though there are more than 10 points available. Thus, students should put in as much correct and relevant information as possible. In the short free response, there are three 3-point and three 4-point questions. Students should spend 3-10 minutes on each one.

A simple four-function calculator (with square root) is allowed on the entire exam, a change made in 2013. No graphing calculators are permitted. Students will also be supplied with a formula sheet (see below sample questions); this is also a change made in 2013.

Since the changes made for the May 2013 exam, scoring a 5 on the exam is much more difficult. (Along the same idea, scoring a 1 is also significantly more difficult!) Here is the grade distribution for the exam.

Score
2008
2009
2010
2011
2012
2013
5
18.50%
19.50%
18.70%
18.80%
19.40%
5.40%
4
15.60%
15.50%
15.10%
16.50%
16.90%
21.40%
3
16.10%
15.80%
15.40%
15.20%
14.30%
36.30%
2
15.20%
15.10%
14.10%
14.60%
14.60%
29.50%
1
34.60%
34.00%
36.60%
34.80%
34.80%
7.40%
Mean
2.68
2.71
2.65
2.7
2.72
2.88
  1. Pick up study guides that were newer than (or made during) 2013. Although the content will remain the same, the format has altered. Most popular study guides are the Baron’s and Cliff Note’s ones. But don’t cram. Study as you go.
  2. Interactive flash cards like http://www.funnelbrain.com/sid-5128-ap-biology-exam-review.html is very helpful for reviewing content.
  3. Youtube is extremely helpful. Youtube channel Bozeman Science (>20 years as a teacher) teaches all the 7 Science Practice and 55 Essential Knowledge.
    Link: http://www.youtube.com/user/bozemanbiology?feature=watch
  4. Scroll to the bottom of the page to see printer-friendly outlines for labs and essential topics covered on the exam: http://www.course-notes.org/Biology
  5. Do not worry about grammar and spelling, but make your writing legible and understandable.
  6. Have students peer review the free response questions of other students. This way, they can see strengths and weaknesses when answering these questions. Also provide them with examples of high scoring answers to emulate.
  7. Partial credit is given in the free response questions, so answer each part as fully as you can.
  8. Mark down the date of the exam (May 12, 2014).
  1. Know key direction words on essays, like:
    1. Explain (make it understandable)
    2. Describe (give properties of)
    3. Discuss
    4. Identify
  2. Look out for tricky words like except, least, most, not, incorrectly, does not belong, etc. Use POE (process of elimination).
  3. Read the questions on the free response carefully. Make sure that you know exactly what you are trying to solve before you begin cranking out information and formulas.
  4. Many free response questions will be based on labs students have completed in their AP biology classes, so students need to attend and understand them.
  5. Chemistry is not required, although it may help on topics like enzymes and DNA.
  1. Simple cuboidal epithelial cells line the ducts of certain human exocrine glands. Various materials are transported into or out of the cells by diffusion. (The formula for the surface area of a cube is 6 × S2, and the formula for the volume of a cube is S3, where S = the length of a side of the cube.) Which of the following cube-shaped cells would be most efficient in removing waste by diffusion?



  2. When DNA replicates, each strand of the original DNA molecule is used as a template for the synthesis of a second, complementary strand. Which of the following figures most accurately illustrates enzyme-mediated synthesis of new DNA at a replication fork?



  3. The following is a food web for a meadow habitat that occupies 25.6 km2. The primary producers’ biomass is uniformly distributed throughout the habitat and totals 1,500 kg/km2.



    Developers have approved a project that will permanently reduce the primary producers’ biomass by 50 percent and remove all rabbits and deer. Which of the following is the most likely result at the completion of the project?
    1. The biomass of coyotes will be 6 kg, and the biomass of hawks will be 0.5 kg.
    2. The biomass of coyotes will be dramatically reduced.
    3. The coyotes will switch prey preferences and outcompete the hawks.
    4. There will be 50% fewer voles and 90% fewer hawks.

  4. A pathogenic bacterium has been engulfed by a phagocytic cell as part of the nonspecific (innate) immune response. Which of the following illustrations best represents the response?



  1. Use the graph above to calculate the mean rate of population growth (individuals per day) between day 3 and day 5. Give your answer to the nearest whole number.



  2. In a certain species of flowering plant, the purple allele P is dominant to the yellow allele p. A student performed a cross between a purple-flowered plant and a yellow-flowered plant. When planted, the 146 seeds that were produced from the cross matured into 87 plants with purple flowers and 59 plants with yellow flowers. Calculate the chi-squared value for the null hypothesis that the purple-flowered parent was heterozygous for the flower-color gene. Give your answer to the nearest tenth.

Link to 2013 free-response:
http://media.collegeboard.com/digitalServices/pdf/ap/apcentral/ap13_frq_biology.pdf

Link to 2002-2007 free-response:
http://www.tutorfox.com/apbiologyarticle.html

Color
Wavelength (nm)
Violet
380-450
Blue
450-475
Cyan
475-495
Green
495-570
Yellow
570-590
Orange
590-620
Red
620-750
  1. An absorption spectrum indicates the relative amount of light absorbed across a range of wavelengths. The graphs above represents the absorption spectra of individual pigments isolated from two different organisms. One of the pigments is chloropyll a, commonly found in green plants. The other pigment is bacteriorhodopsin, commonly found in purple photosynthetic bacteria. The table above shows the approximate ranges of wavelengths of different colors in the visible light spectrum.

    1. Identify the pigment (chloropyll a or bacteriorhodopsin) used to generate the absorption spectrum in each of the graphs above. Expalin and justify your answer.
    2. In an experiment, identical organisms containing the pugment from Graph II as the predominant light-capturing pigment are separated into three groups. The organisms in each group are illuminated with light of a single wavelength (650 mm for first group, 550 mm for the second group, and 430 mm for the third group). The three light sources are of equal intensity, and organisms are illuminated for equal lengths of time. Predict the relative rate of photosynthesis in each of the three groups. Justify your predictions.
    3. Bacteriorhodopsin has been found in aquatic organisms whose ancestors existed before the ancestors of plants evolved in the same environment. Propose a possible evolutionary history of plants that could have resulted in a predominant photosynthetic system that uses only some of the colors of the visible light spectrum.
  1. Matter continuously cycles through an ecosystem. A simplified carbon cycle is depicted below.

    1. Identify the key metabolic process for step I and the key metabolic process for step II, an briefly explain how each process promotes movement of carbon through the cycle. For each process, your explanation should focus on the role of energy in the movement of carbon.
    2. Identify an organism that carries out both process.
Sample Questions (Section 1 Part A):
1. Answer: A

Essential Knowledge: Organisms must exchange matter with the environment to grow, reproduce, and maintain organization.
Science Practice: The student can apply mathematical routines to quantities that describe natural phenomena.
Learning Objective: The student is able to use calculated surface area-to-volume ratios to predict which cell(s) might eliminate wastes or procure nutrients faster by diffusion.

2. Answer: D

Essential Knowledge: DNA, and in some cases RNA, is the primary source of heritable information.
Science Practice: The student can describe representations and models of natural or man-made phenomena and systems in the domain.
Learning Objective: The student is able to describe representations and models that illustrate how genetic information is copied for transmission between generations.

3. Answer: B

Essential Knowledge: Interactions among living systems and with their environment result in the movement of matter and energy.
Science Practice: The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively.
Learning Objective: The student is able to use visual representations to analyze situations or solve problems qualitatively to illustrate how interactions among living systems and with their environment result in the movement of matter and energy.

4. Answer: C

Essential Knowledge: Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis.
Science Practice: The student can describe representations and models of natural or man-made phenomena and systems in the domain.
Learning Objective: The student can create representations and models to describe immune responses.

Sample Questions (Section 1 Part B):
1. Answer: 340-360

Essential Knowledge: Natural selection is a major mechanism of evolution.
Science Practice: The student can apply mathematical routines to quantities that describe natural phenomena.
Learning Objective: The student is able to apply mathematical methods to data from a real or simulated population to predict what will happen to the population in the future.

2. Answer: 5.3-5.4

Essential Knowledge: The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring.
Science Practice: The student can apply mathematical routines to quantities that describe natural phenomena.
Learning Objective: The student is able to apply mathematical routines to determine Mendelian patterns of inheritance provided by data.

Sample Questions (Section 2, long and short free responses):
Answer: http://media.collegeboard.com/digitalServices/pdf/ap/apcentral/ap13_biology_q2.pdf

a. (3 points)

  1. Identify the pigment (chloropyll a or bacteriorhodopsin) used to generate the absorption spectrum in each of the graphs above. Expalin and justify your answer. (3 points maximum)
1 point per box
Identify BOTH pigments:
Graph 1 = bacteriorhodopsin AND graph 2 =chloropyll a
Explain that an organism containing bacteriorhodopsin appears purple because the pigment absorbs light in green range of the light spectrum and/or reflects violet or red and blue light.
The reflected red and blue light appears purple.
Explain that an organism containing chloropyll a appears green because the pigment absorbs light in the red and blue ranges of the light spectrum and/or reflects green light.

b. 5 points

  1. In an experiment, identical organisms containing the pugment from Graph II as the predominant light-capturing pigment are separated into three groups. The organisms in each group are illuminated with light of a single wavelength (650 nm for first group, 550 nm for the second group, and 430 nm for the third group). The three light sources are of equal intensity, and organisms are illuminated for equal lengths of time. Predict the relative rate of photosynthesis in each of the three groups. Justify your predictions. (5 points maximum)
Wavelength
(Group)
Prediction
(1 point each box)
Justification
(1 point each box)
650 nm
(1st Group)
Intermediate rate An intermeditate level of absorption occurs at 650 nm (compared to 430 nm and 550 nm); therefore, an intermediatre amount of energy is available to drive photosynthesis.
550 nm
(2nd Group)
Lowest rate The lowest level of absorption occurs at 550 nm; therefore, the least amount of energy is available to drive photosynthesis.
430 nm
(3rd Group)
Highest rate The highest level of absorption occurs at 430 nm; therefore, the least amount of energy is available to drive photosynthesis.

NOTE:: A student who combines two groups (e.g., "the 650 nm and 430 nm groups have higher rates of photosynthesis compared to the 550 nm group") can earn a maximum of 4 points: up to 2 points for the prediction and up to 2 points for the justification.

c. (2 points)

  1. Bacteriorhodopsin has been found in aquatic organisms whose ancestors existed before the ancestors of plants evolved in the same environment. Propose a possible evolutionary history of plants that could have resulted in a predominant photosynthetic system that uses only some of the colors of the visible light spectrum. (1 point per box; 2 points maximum)

Proposal that includes an environmental selective pressure:

  • Green light was being absorbed by aquatic organisms using bacteriorhodopsin
  • Unabsorbed wavelengths of light were available resources that organisms could exploit.
  • Absorbing visible light at all wavelengths may provide too much energy to the organism.
  • Absorbing light from ultraviolet wavelengths (shorter wavelengths = higher energy) could cause damage to the organism.
  • Absorbing lights with longer wavelengths may not sufficient energy for the organism.

Appropriate reasoning to support the proposal:

  • Natural selection favored organisms that rely on pigments that absorbs available wavelengths of light.
  • Endosymbiosis: chloraplasts evolved from cyanobacteria with pigments that used only certain wavelengths.
  • Genetic drift eliminated pigments that absorbed certain wavelengths of light.
  • Mutation(s) altered the pigment(s) used by organisms.

4. Answer: http://media.collegeboard.com/digitalServices/pdf/ap/apcentral/ap13_biology_q4.pdf

a. (3 points)

  1. Identify the key metabolic process for step I and the key metabolic process for step II, an briefly explain how each process promotes movement of carbon through the cycle. For each process, your explanation should focus on the role of energy in the movement of carbon.

Identification: 1 point maximum

I = photosynthesis / Calvin cycle

AND

II = (cellular) respiration / critic acid cycle / Krebs cycle

Explanation: 1 point each row, 2 points maximum

Process Carbon Input Role of Energy in the Movement of Carbon Carbon Output
Photosynthesis CO2 is fixed Uses (light) energy or ATP from light reaction Organic molecules
(Cellular)
Respiration
Organic molecules are hydrolyzed / broken down Uses energy for cellular processess such as growth adn / or ATP production CO2

b. (1 point)

  1. Identify an organism that carries out both process. (1 point maximum)
    • Plant
    • Algae
    • Photosynthetic protist (e.g., Euglena)
    • Cyanobacterium
    • CO2 fixing bacterium
    • Lichen (not fungus)

Formula Sheet: Even though this is provided on the exam, students must be familiar with what the formulas mean and when to apply them.http://media.collegeboard.com/digitalServices/pdf/ap/IN120084785_BiologyCED_Effective_Fall_2012_Revised_lkd.pdf