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.