Cracking the AP Biology Exam

15

Laboratory

LAB 12: DISSOLVED OXYGEN AND AQUATIC PRIMARY PRODUCTIVITY

In this lab, the concentration of oxygen dissolved in water samples was examined using the Winkler technique. The Winkler technique is a way of measuring the amount of dissolved oxygen in water.

What are the general concepts you really need to know?

  • Gases such as carbon and oxygen are always recycled in our ecosystem
  • Three factors affect the solubility of dissolved gases in aquatic ecosystems: temperature, salinity, and photorespiration. Temperature and salinity decrease dissolved oxygen concentration. Photorespiration increases oxygen concentration.
  • Know the concept of primary productivity. The rate at which producers in an ecosystem store energy is called the primary productivity. Primary productivity is determined by the rate at which oxygen is produced.
  • Also know the difference between gross and net productivity. Gross productivity is the total energy obtained by organisms, whether through photosynthesis or ingestion. Net productivity is the rate at which energy is incorporated into bodies to produce growth.