Question 1. Amphibians (e.g., frogs, toads, and salamanders) are declining world
ID: 280715 • Letter: Q
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Question 1. Amphibians (e.g., frogs, toads, and salamanders) are declining worldwide. Two hypotheses for why this is happening are predators and pesticides. To test these hypotheses, scientists raised several frog species as tadpoles in small ponds (n = 5 per treatment combination). Ponds had either no predators, predatory newts, or predatory beetle larvae; in addition, ponds were exposed to either no pesticide (NP), the insecticide Malathion (M; kills insects) or the herbicide Roundup (R; kills plants), two globally common pesticides. The researchers then monitored subsequent survival of the tadpoles in each pond. Consider the following figure; different letters denote statistically significant differences between groups (Tukey's HSD; P0.05): 100- A AB a) 80 60 S 20 0 No Predator Newts Beetles A. What is/are the independent and dependent variable(s) in this study? B. How many treatment combinations are there in this experimental design and which one is the control group? C. What is the experimental unit in this study and how many replicates are there for each treatment combination? D. Not considering pesticides, what effect did predators have on tadpole survival? Explain. E. Not considering predators, what effect did pesticides have on tadpole survival? Explain. F. Given the overall results of this experiment, what management recommendation would you make if your goal was to maximize amphibian survival (e.g., ban Malathion, Roundup, or both)? Explain.Explanation / Answer
A. dependent variable- tadpole survival percentage
independent variables- treatment with pesticides and predator
B. there are 9 treatment combinations.
no predator+ no pesticide would act as the control group.
C. experimental unit in the study- tadpole survival percentage in the presence of various combinations of predators and pesticides.
there are 5 replicates for each treatment combination.
D. not considering pesticides, predators have a negative effect on the tadpole survival, i.e, the presence of predators (in the absence of pesticides) resulted in decreased tadpole survival compared to the control. both newts and beetles in the absence of pesticides decreased the tadpole survival.
E. not considering predators, pesticide malathion has no considerable effect on the tadpole survival. herbicide Roundup decreased the tadpole survival.
F. based on the results of the study, both the predators, newts and beetles decreased the tadpole survival.
malathion have no significant effect on the tadpole survival. however, Roundup decreased the tadpole survival.
the recommendation would be no predator + no pesticide combination or no predator + malathion combination to increase tadpole survival.
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