Cracking the AP Biology Exam
14
The Free-Response Questions
GRADING CHECKLIST
To help you grade this sample essay, we’ve put together a checklist that you can use to calculate the number of points that should be assigned to each part of this question. We’ll first explain the important points on the checklist, and then give you sample essays to show you how test reviewers would evaluate them.
ESSAY CHECKLIST
Part a: Types of Nutritional Requirements—4 Points Maximum
Angiosperms:
1 point—Autotrophs—if defined
1 point—They require H2O, CO2, and minerals.
Vertebrates:
1 point—Heterotrophs—if defined
1 point—They require organic compounds (sugars, proteins, fats), H2O, vitamins, and minerals.
Part b: Structures in Angiosperms—4 Points Maximum
First two structures only
(1 point each) |
(1 point each) |
Structure |
Function described |
Cuticles |
Prevent desiccation |
Stomata |
Pores in leaf that regulate gas exchange |
Lenticels |
Pores in stems that regulate gas exchange |
Palisade mesophyll |
Loosely packed cells in a leaf; contains chloroplasts |
Roots |
Structures that absorb water and minerals |
Root hairs |
Extensions of the root that increase the surface area for water absorption |
(1 point)
Carnivorous plants (such as Venus flytrap) have modified leaves to trap insects.
Part c: Symbiotic Relationships—4 Points Maximum
First 2 relationships only
(1 point each) |
(1 point each) |
Relationship |
Benefits to Each |
Nitrogen-fixing bacteria |
Bacteria get food/Plants get usable nitrogen |
Mycorrhizae |
Fungi get food/Plants get water and minerals |
Intestinal bacteria |
Humans get Vitamin K/Bacteria have a place to live |
Ruminants flora |
Bacteria digest the cellulose for cows/Bacteria have a place to live |
Wood-eating termites |
Protists digest wood/Termites obtain the wood |
EXPLANATION OF CHECKLIST
For Part a, you’ll receive points if you demonstrate a clear understanding of the terms autotroph and heterotroph. You must define the terms and describe the necessary nutrients for both angiosperms and vertebrates. For angiosperms, you have to mention the raw materials for photosynthesis (CO2 + H2O) and minerals. For vertebrates, you have to mention organic compounds and additional vitamins or minerals.
For Part b, you have to relate structure to function. Which structures are involved in obtaining nutrients? You’re asked to discuss two structures in angiosperms. One point is given for the structure and another point is given if you show a clear understanding of the function of the structure.
For Part c, you are asked to give two examples of symbiotic relationships. Since they ask for only two examples, you earn points only for the first two examples. An additional point is also given if you describe the benefits to each organism.
Notice that you don’t have to know everything about biology to get a high score on the essay section. However, you do have to present the proper information with a certain level of detail. Additionally, you can earn a maximum of 4 points for each part. However, you can’t earn more than 10 points total.
Before you use this checklist to assign points to your essay, let’s evaluate two sample essays.