Ap Bio Pre Lab

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  • Topic: Oxygen, Error, Temperature
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Dissolved Oxygen and Aquatic Primary Productivity

By: Mayank Makwana
AP Biology
Mrs. Biondo
September 19, 2012

Design Diagram

Dissolved Oxygen:

Title: The effect of the temperature of water on the concentration of dissolved oxygen

Hypothesis: If the temperature of the water is increased, then the concentration of dissolved oxygen will decrease.

|Independent Variable: Temperature of water (Cº) | |Temperatures |

Light Intensity |Initial |Dark |100% |65% |25% |10% |2% | |Trials |1 |1 |1 |1 |1 |1 |1 | | Dependent Variable: Primary Productivity (Gross and Net in mg/L) Constants: Source of lake water, amount of lake water, pH of lake water, water sampling bottles, plastic window screens

Abstract

The survival of all organisms in the world is largely dependent on oxygen. For land dwelling organisms, the oxygen needed by them is obtained from the air, but for organisms that live in the water, their oxygen has to be obtained from the water. The amount of oxygen that these organisms can take from the water is hugely dependent on the dissolved oxygen content in the water. The purpose of the two experiments done in this lab was to see the ideal condition to produce the most dissolved oxygen concentration. We approached the challenge of finding the ideal condition by testing two different variables in two different experiments. In the first experiment, we tested the different temperatures of water to see which temperature produced the highest concentration of dissolved oxygen. In the second experiment, we added plants to pond water, changed the amount of light for each beaker (to simulate increasing depth), and then recorded the dissolved oxygen content after waiting for approximately 1 day to see which depth produced the highest amount of dissolved oxygen. In the data we collected, for the first experiment, we found that the colder water had the most dissolved oxygen content. For the second experiment, we discovered that the most light (least depth) had the highest dissolved oxygen concentration. Though the results of our experiment are not world changing, they demonstrate the profound effect of temperature and light exposure on the life of water organisms.

Introduction

Terminology:

Dissolved Oxygen- The amount of free oxygen dissolved in water

Primary Productivity-The rate at which organic materials (carbon containing compounds) are stored.

Net Productivity- The measure of the change overtime in dissolved oxygen concentration from the initial concentration.

In this lab, we are exploring the ideal conditions in which dissolved oxygen concentrations are the highest. To figure this out we are conducting two different experiments, in which we are testing two distinct variables. In the first experiment, we are testing the effect of temperature on the dissolved oxygen concentration. The temperatures we are using are 21º C, 30º C, and 5º C. In the second experiment, we are testing the dissolved oxygen concentrations at different depths adding plants to show the processes of photosynthesis and respiration. The different depths are being represented with screens that let in different amounts of light. We are adding 0 screen layers to represent 100% light, 1 screen layer to represent 65% light, 3 screen layers to represent 25% light, 5 screen layers to represent 10% light, and 8 screen layers to represent 2% light. The main piece of equipment used in both labs was a dissolved oxygen test kit, which was used to test the dissolved oxygen concentration in the different samples. For the first experiment, my hypothesis was if the temperature of the water is increased, then the concentration of dissolved oxygen will...
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