Ecosystem lab: Biological magnification of DDT at each trophic level
Name: _______________
Date: _________________
Period: _______________
PRELAB QUESTIONS
Write definitions of the following terms.
Food chain:
Producer:
Consumer:
Autotroph:
Heterotroph:
INTRODUCTION
DDT, a powerful insecticide, was widely used in the mid 1900s in the United States, but its harmful effects on the environment made people stop using it in 1972. DDT remained in organisms’ bodies without being broken down. Large carnivorous birds especially were vulnerable to DDT and laid eggs with thin shells because of the effects of DDT (Solomon, Berg, and Martin, 2008).
A food chain shows “energy flow in an ecosystem” (Solomon, Berg, and Martin, 2008, p. G-17).
In other words, it shows which organism consumes which organism and which organism decomposes which organism in a linear way. A food chain usually has producers, consumers of different levels, and decomposers. Producers are usually autotrophs and use photosynthesis to produce energy. Consumers feed on producers or other consumers and are heterotrophs. A trophic level is each level or step of an organism in terms of its role (producers, consumers, secondary consumers, etc.) in a food web (Solomon, Berg, and Ma rtin, 2008). You will be given the data of DDT concentrations of organisms at each trophic level in the same food chain. Your job is to draw a graph based on the data and analyze the results.
HYPOTHESIS
Will the DDT concentration increase or decrease at each trophic level of a food chain? (In other words, will consumers have more DDT concentration than producers?)
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OBJECTIVES
Students will be able to write a hypothesis about the amount of DDT concentrations within a higher trophic level.
Students will be able to check whether their own hypothesis was correct or not using the results of the data.
Students will be able to assign each organism’s role in terms of a trophic level.
Students will be able to draw a food chain using the relationship between organisms.
Students will be able to graph the amount of DDT concentration at each trophic level using the data given.
Students will be able to explain why the DDT amount changes as the trophic level changes.

MATERIALS
Graphing paper
Pencils
Lab handouts
SAFETY
NA
PROCEDURES
In a study by Woodwell, Wurster, and Isaacson (1967), scientists measured DDT residues (DDT that remains in an organism’s body) in different organisms at different trophic levels. This study was done in
Long Island, New York. They used gas chromatograph to measure the amount of DDT in thirty-nine plants and animals in the area. (Table 1 shows the data of five organisms that are in the same food chain.)
OBSERVATION/DATA
Table 1. DDT concentrations in samples
Sample
Plankton
Shrimp
Atlantic needle fish
Ring-billed gull
Amount of DDT residues (ppm) in tissue
0.04 ppm
0.16 ppm
2.08 ppm
75.5ppm
1.
Draw arrows between the pictures of organisms below to create a food chain. Label each organism with a proper trophic level (i.e. producers and consumers; herbivores are primary consumers, and carnivores are secondary or tertiary consumers. Animals that eat secondary consumers are tertiary consumers.)
Plankton:
Shrimp:
Atlantic needle fish:
Ring-billed gull

2.
Using the data in table 1, draw a graph of the DDT residues for each trophic level. (Include a title, x and y axes, and their units.)

ANALYSIS QUESTIONS
1.
Does the result support your hypothesis on page 1? Why or why not? Explain your answer.
2.
Why do you think the concentration of DDT changes at each trophic level in the way it does? Why were large carnivorous birds especially vulnerable to DDT? (Hint: DDT is not digested or excreted but remains in the body of an organism.)
Extra credit: Use the Internet or books to find effects of DDT on human bodies.
References
Dave, S. (2007). [Illustration].Wet Canvas. Retrieved from http://www.wetcanvas.com/forums/showthread.php?t=395602
Phytoplankton. (n.d.). [Illustration]. Retrieved from http://jrscience.wcp.muohio.edu/climate_projects_05/productivity/Phytoplankton.html
Solomon, Berg, and Martin. (2008). Biology. Belmont, CA: Thomson Higher Education. pp. 1171-1172.
Virginia Institute of Marine Science. (2013). Information from FAO Species Identification Guide Western Central Atlantic
Northern brown shrimp - Farfantepenaeus aztecus. Retrieved from http://www.vims.edu/research/departments/fisheries/programs/multispecies_fisheries_research/species_data/brown_shrimp/index.php
Wikimeida. (2010). [Illustration]. Garfish (Atlantic Needlefish). Retrieved from http://commons.wikimedia.org/wiki/File:Garfish_(Atlantic_Needlefish)_(PSF).png
Woodwell, G.M., Wurster Jr,C.F., and Isaacson, P.A. (1967). DDT Residues in an East Coast Estuary: A Case of Biological Concentration of a
Persistent Insecticide. Science, 156 (3776 ). pp. 821-824 DOI: 10.1126/science.156.3776.821