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Animal Behavior: Predict and Justify


C. elegans, a nematode or "round worm," is a model organism in biology. A group of AP biology students was investigating associative learning in C. elegans.

C. elegans feeds on bacteria, a particular strain of E. coli OPI150. For one week, when students added E. coli OPI150 to the nematode culture, they also added salt ($NaCl$). Then, students placed the nematodes on a Petri dish with two choices, one mL of $NaCl$ solution and one mL of water, as seen in the image below.

Which of the following predicts and justifies where the C. elegans will be located after ten minutes in this experiment?

Created by J. Edgar for Albert.io. Copyright 2016.


The worms will move toward the $NaCl$ since the $NaCl$ is combined with E. coli in the choice chamber.


The worms will move toward the water since E. coli rapidly populate in water solutions.


The worms will move toward the $NaCl$ since they associate this solution with E. coli food source.


The worms will move randomly, neither toward the $NaCl$ or the water since no E. coli food source is present.