SCIENCE 911: Panama Protection Racket
When Thisbe caterpillars are attacked by wasps, who do they call for help? Ants. Although most ants wouldn't have anything to do with a Thisbe, one species is happy to provide protection because it's worth the payoff -- a special nectar produced by the caterpillar. Biologist Philip DeVries travels to the rain forests of Panama to investigate the secrets of this intricate relationship.
Notes & Discussion
Activity: Symbiotic Scenarios
Report From the Field: Philip J. DeVries, Tropical Field Biologist
NOTES & DISCUSSION
- What characterizes a symbiotic relationship? (In a symbiotic relationship between two species, one member always benefits. The other may also benefit, or it may be harmed or unaffected.) How is the relationship between the singing caterpillars and the ants seen on Frontiers an example of symbiosis? The ants provide a valuable service for the Thisbe caterpillars; what do the ants gain in return?
- Define and find examples of each of the three types of symbiosis: mutualism, commensalism, parasitism.
- Do you think that Thisbe caterpillars and ants exhibit mutualism or commensalism? A Thisbe could not survive without its defenders, but the ants could live without their sweet-secreting host. It could be argued that an ant's reward for defending the Thisbe is transient and therefore constitutes commensalism. However, if the treat is really food, and helps keep the ant alive, then the relationship could be considered as an example of mutualism. You decide.
- Do you agree or disagree with this statement: all organisms live in some kind of symbiotic relationship. Do the relationships between inhabitants in an ecosystem constitute symbiosis? Choose an ecosystem and brainstorm all the symbiotic relationships you can think of within five to ten minutes.
- What steps does biologist Philip DeVries take to prove his theories? You will find a more detailed account of the Thisbe-ant story written by DeVries in "Singing Caterpillars, Ants and Symbiosis" in Scientific American, October 1992.
ACTIVITY: SYMBIOTIC SCENARIOS
Identify the living creatures involved in the symbiotic relationships described here. What you find out may change the way you think about teamwork.
Strange and Unusual Partners
Living creatures -- both plant and animal -- frequently exhibit unusual partnerships. In some associations, both benefit. In others, one species gains more than the other. You saw an example of one kind of partnership between ants and caterpillars on Frontiers. With a little bit of research, you can solve the mysteries described here. Each presents a different symbiotic scenario. First, read each description, and then:
- Identify the organisms involved in the relationship, choosing from the list that follows.
- Write a brief description of the actual relationship.
- Identify the type of symbiosis exhibited.
- "My friend is really nice to me. He always leaves me scraps of food and protects me from the really big guys. As long as I've been hanging around him, he's never once bitten me. He says he doesn't mind my being there, and I'm glad." Who are we?
- "We're best friends! I provide nutrients for my friend, and in return I get water, protection from dryness, protection from bright light and essential nutrients. We're really close. We couldn't live without each other." Who are we?
- "I love my friend. She gives me a warm home and all the food I can eat. I've grown 40 feet since I moved in! I may have to look for a new residence soon, though. I think my friend got sick and won't be around much longer." Who are we?
- "I'm the perfect life form and I offer my friend the chance to become just like me. In fact, I gave him my very own genetic code. He doesn't seem to be too grateful, though. I think I'll just move on and leave him alone because he sent an army after me!" Who are we?
- "My friend is thousands of times bigger than I am, and feeds on the nutrients I need to survive. Part of me grows inside her and the rest stays outside. In return, I keep her alive by donating a gas she absolutely needs. Without me she would die!" Who are we?
- "My friend is nasty! But I don't mind. It doesn't bother me. In fact, the thugs that want to make a meal out of me are scared to mess with me when I'm hiding in her arms. My friend doesn't complain about me at all. In fact, she ignores me." Who are we?
- mycorrhizae and tree
- pilot fish and shark
- shrimp and anemone
- tapeworm and human
- virus and human
- alga and fungus (lichen)
Create scenarios for the following symbiotic relationships:
- flea and friend
- rhinoceros and tickbird
- mosquito and person
- mistletoe ants and aphids
- plover and crocodile
Resources: You'll find information about symbiotic relationships in biology texts or library books.
- pilot fish and shark/commensalism
- virus and human/parasitism
- mycorrhizae and tree/mutualism
- shrimp and anemone/commensalism
- Use the lab activity for this segment when you study ecological systems. The story featured on Frontiers applies to life science, especially to the study of insects.
On the TV show Star Trek: Deep Space Nine, a humanoid has allowed herself to be occupied by a symbiont. The symbiont has lived for many generations in different hosts. The hosts are not harmed in any way. It could be argued that this arrangement is an example of either commensalism or mutualism.
Write a science fiction story using any or all examples of symbiosis. Choose two different life forms, either actual or fictitious. Set up a scenario of their relationship based on scientific fact.
CREDIT: This activity was contributed by Earth science teacher and curriculum consultant Frank Weisel. He is developing a curriculum that will integrate the secondary sciences.
REPORT FROM THE FIELD: PHILIP J. DEVRIES, TROPICAL FIELD BIOLOGIST
On this segment of Frontiers, we meet Philip DeVries, a biologist with special expertise in plant-animal interactions. In his work in rain forest regions, DeVries has discovered new species of plants, butterflies and other insects. "More than anything," he says, "I enjoy discovering things. That's what I do for a living -- and I do it in natural settings."
Among his most exciting discoveries is finding that caterpillars produce a call -- something we see firsthand on Frontiers. DeVries believes that it's possible to discover something new almost every time he goes into the rain forest. "These regions are filled with plants and animals and interactions that are completely unexplored -- we know nothing about them." But scientists who do what he does are scarce, says DeVries, and there's little encouragement in university systems for students to pursue whole-organism biology.
After spending years searching for wild areas in the tropics, DeVries has insights into how these quickly diminishing areas can be protected. "The preservation of biodiversity, habitats and wilderness areas -- just nature as we know it -- is important," he states. "But it's entirely in the hands of kids. "He believes that today's students will need to take a stand to ensure that vital research continues. "If students really want to know about organisms and understand the tropics, they can work in these areas with biologists like myself. It's hard work, but there are people who would be willing to have these students work for them. They have to convince the system they're in that this work is important -- and demand that it be done."
Philip DeVries received his doctorate from the University of Texas in 1987 and is a recipient of the prestigious MacArthur Foundation Fellowship. His field guide, Butterflies of Costa Rica, is published by Princeton University Press, and he is currently at work on a second book.
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