Antarctic Undersea Foodweb

Overview

Using photos from a variety of websites, including the PolarTREC and SCINI websites, students will identify organisms to phylum and/or class level (e.g. polychaetes, starfish, brittle stars, sponges) and then research the primary foods that these organisms eat. They will then develop a simple food web for these organisms.

Objective

1. Students will identify eight to ten Antarctic undersea organisms to phylum and/or class from website photos.

2. Students will research the trophic (feeding) relationships of these organisms. Learner vocabulary will include: producers, consumers, herbivores, omnivores, carnivores, filter-feeders, detritivores, scavengers, decomposers, and predators. Students will create an undersea Antarctic food web for these organisms.

Preparation

Teachers need to have access to photos for students to use. If students have access to the internet, they can do this themselves. If the students cannot access the internet, or to save time, the teacher can print out photos for students to use. Laminating the photos will allow them to be used over and over again. Resources for identifying organisms (most biology books and the Undersea Field Guide are helpful) and information on how the organisms gain energy (“eat”) is needed. The teacher needs an understanding of food webs and how they can be diagrammed or illustrated. Numerous examples of this exist in textbooks and on the web.

Procedure

1. Engage: What do you think of when you think of Antarctica? What organisms live on the continent? Why aren’t there very many organisms? What organisms do you think live underwater in Antarctica? Show slides of some of these organisms to engage student interest. Why are there so many more organisms under the ice than on the ice? Stimulate student discussion. The undersea environment has more stable environmental conditions (temperatures are fairly steady) and there is food available from producers underwater (diatoms and other phytoplankton as well as some algae) whereas the environmental conditions on the ice are extreme and varied, and there are limited producers on the ice. Why are so many of these organisms invertebrates? (Invertebrates are animals without a backbone and are supported in the water so can grow larger than most invertebrates on land such as insects and snails.)

2. Explore: In small groups of two or three, the students find photos at listed websites or the teacher provides photos to students. Students list organisms they see. They may use biology textbooks or the underwater field guide (listed) to determine the phylum and/or class of organisms they observe. Using the underwater field guide or biology books, the students determine the main foods that these organisms eat.

3. Explain: Students, in small groups, develop a food web for the organisms. The learners then articulate their food webs to the rest of the class. The teacher and class can evaluate whether the food web seems accurate based on their knowledge. What types of feeding behavior have the students identified in their food web?

4. Extend: What would happen if a disease took out all of the starfish? (The starfish are predators on the sponge, so the sponge population would increase. Paul Dayton’s experiments, described on both the SCINI and PolarTREC websites, used floating platforms or strings to enable sponges to get off the seafloor and away from the starfish. These sponges were able to grow much larger away from the predatory starfish.)

• What kind of larvae do these organisms have? How can they distribute themselves in the seascape? (Some of the organisms have swimming larvae and can spread to new areas more easily. Other organisms have offspring that cannot travel as far.)

5. Evaluate: Did the students identify eight to ten organisms and their trophic relationships? Did the students understand the roles of each organism in this polar undersea ecosystem?

Extension

Learners could add more organisms to their food web.

Resources

• Photos for this activity are from the Underwater Field Guide to Ross Island & McMurdo Sound, Antarctica Field Guide, Dr. Stacy Kim’s SCINI expedition to Antarctica in October – December 2007 and from the expedition that Mindy Bell participated in.

• A simple key is provided to help teachers guide students to appropriate trophic relationships. Students can present their food web on a small whiteboard, or make a poster with photos of organisms or of illustrated organisms.

Assessment

Informal assessment of each student group as they present their food web. Did they identify eight to ten organisms and their trophic relationships? Did the students understand the roles of each organism in this polar undersea ecosystem?

Credits

Mindy Bell wrote this lesson based on similar activities she has previously done with students in the 6th to 12th grade. You can contact Mindy at mindyscience [at] gmail.com if you have questions about this lesson.