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About This Drill
AP Biology — Unit 8 — Energy Flow & Trophic Levels — Drill 34 is a practice drill. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
Practice quantitative reasoning about energy transfer across trophic levels in this AP Biology drill on Unit 8 ecology. Apply the ecological efficiency formula, interpret energy flow tables, and evaluate claims about ecosystem productivity.
Passage
Ecologists studying a freshwater lake ecosystem measure energy transfer across four trophic levels over one growing season. Energy content is expressed in kilocalories per square meter per year (kcal/m2/yr). Net production represents energy available to the next trophic level after respiration losses.
| Trophic Level | Organism | Gross Production (kcal/m2/yr) | Respiration (kcal/m2/yr) | Net Production (kcal/m2/yr) |
|---|
| 1 | Phytoplankton | 20,000 | 3,000 | 17,000 |
| 2 | Zooplankton | 3,400 | 1,200 | 2,200 |
| 3 | Planktivorous fish | 680 | 320 | 360 |
| 4 | Piscivorous fish | 72 | 50 | 22 |
Questions in This Drill
- Using the data in the table, what is the approximate ecological efficiency from trophic level 1 to trophic level 2?
- Which calculation correctly determines the percentage of energy transferred from trophic level 2 to trophic level 4?
- Based on the data, how much energy is lost to respiration at trophic level 3?
- A researcher proposes that increasing nutrient input to the lake (eutrophication) would increase phytoplankton productivity and therefore proportionally increase energy available at trophic level 4. Which reasoning best evaluates this proposal?
- Which trophic level demonstrates the greatest metabolic cost relative to its energy intake?