Schooling fish Predators might learn to avoid can toads after experiencing the e
ID: 92412 • Letter: S
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Schooling fish
Predators might learn to avoid can toads after experiencing the effects of their toxin. To explore this possibility, researchers fed tadpoles of cane toads to fish that had never experienced this prey. As a control, a second set of fish were fed tadpoles of a native Australian species, which fish routinely consume in nature. After each treatment, both the fish exposed to can toads and the fish naïve to cane toads were offered native tadpoles over a period of 5 days. Finally, the experiment was repeated exactly the same way, except fish were offered crickets after being exposed to cane toad tadpoles or native tadpoles, because crickets neither look nor smell like cane toad tadpoles. The figure below shows the results of the two experiments.
Use this information and your knowledge of biology to answer the following questions.
ANSWER TRUE OR FALSE AND EXPLAIN WHY.
1. Without the second experiment, one could still confidently conclude that fish learned to avoid tadpoles.
2. The sample size in this experiment was the number of tadpoles or crickets fed to each fish.
3. If fish in natural environments experience cane toads, cane toads would have a direct negative effect on these fish.
4. The results suggest that cane toads would have a positive indirect effect on native species of toads.
5. The results suggest that cane toads would have a positive indirect effect on native species that do not have a tadpole stage.
exposed Tadpoles Crickets 5 O 4 exposed 3 naive naive 1 5 10 15 20 25 30 45 600 120 5 10 15 20 25 30 45 60 120 24 h Time (h) Time (h) Figure 1. Two experiments were conducted, in which fish were offered prey after being exposed to cane toad tadpoles (exposed) or being exposed to native tadpoles (naive). In the first experiment, the prey were native tadpoles (left-hand plot). In the second experiment, the pre were crickets (right-hand plot)Explanation / Answer
Answer:
1: FALSE- without the second experiment we cannot confidently conclude the results, as second experiment worked as control from where we can infer that both fish types would consume the same prey unless they learnt that a particular prey is toxic.
2. TRUE- Sample size was that of tadpoles, because the number of tadpoles remaining were accounted and not that of fish.
3. TRUE- because without previous exposure, fish won't be able to differentiate the toxic toad and feed on them. The toxin will have direct effect on the fish preying on them.
4. TRUE - because the cane toad would poison many predators and indirectly the native species would be left with lesser predators. Also, due to similarity in appearance , predators would not prey on native tadpoles.
5. FALSE: if there is no tadpole stage, it won't much benefit a native species, as predators can distinguish the adult forms of different species.
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