6. Devil\'s gardens are stands of a single specics of tree, Duroia hirsuta. One

Question

6. Devil's gardens are stands of a single specics of tree, Duroia hirsuta. One hypothesis
is that ants living in these trees produce a poisonous chemical that kills trees of other
species. Another hypothesis is that Duroia trees themselves kill competing trees
perhaps by means of a chemical they secrete (a process called allelopathy). To test
these hypotheses, Megan Frederickson carried out field experiments in Peru. Two
saplings of a local nonhost tree specics, Cedrela odorata, were planted inside each of
ten devil's gardens. At the basc of one, a sticky insect barrier was applied; the other
was unprotected. Two more Cedrela saplings, with and without barriers, were
planted about 50 meters outside each garden. See Figure below. The researchers
observed ant activity on the Cedrela lcaves and measured areas of dead leaf tissue

after one day. What kind of data would support
a. The first hypothesis
b. The second hypothesis

EXPERIMENT Cedrela sapling Insect barrier Duroia tree Outside, protected Inside, unprotected Inside, protected Devil's garden Outside, unprotected Consider the study described below. What are the problems associated with this study? Explain. If you were to redesign this study, what would be the independent variable? The dependent variable? The sample size? The control treatment? Be prepared to do this kind of analysis for any given scenario. 7. 150 patients with Crohn's disease are given an experimental treatment in which they all drink "cocktails" containing thousands of pinworm eggs. Within one week, 72% of the patients report a reduction in their abdominal pain. Is ingesting pinworm eggs an effective treatment for the symptoms of Crohn's disease?

Explanation / Answer

a) When the Cedrela saplings not covered by insect barriers are affected and those covered by insect barriers are unaffected, it supports the first hypothesis which states that ants living in Duroia trees produce chemicals that kills the trees of other species.

b) When both the Cedrala saplings that are covered by insect barrier and those not covered by it are affected, it supports the second hypothesis which states that the Duroia trees secretes chicks that kills other trees (allelopathy).

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