Predation as an Agent of Natural Selection
In this experiment, Daphnia will serve as a predator on our ciliates. Obviously, being eaten is not a great strategy for survival, avoiding predators is a much better strategy. The relevance here is that characteristics of ciliates that make them more susceptible to predation are maladaptive traits. Traits that allow them to avoid predation are adaptive.Daphnia are not visual predators, in fact “predator” can only be used loosely, as Daphnia are filter-feeders, trapping and eating particles in the water column rather than singling out a prey item for capture. Because they mostly eat algae, they tend to feed where algae are most abundant, in the photic zone (or part of the water column with light penetration).
So, this creates an interesting situation for our ciliates. Our photosynthetic phenotype (Paramecium bursaria) is phototactic, they move toward light. Phototactic behaviour gives them an adaptive advantage. It allows this phenotype to use light to fix carbon, supplementing bacteria as a food source. As a result, light would seem to exert a natural selection pressure that favours our photosynthetic phenotype. However, phototaxis also brings our photosynthetic phenotype into close contact with a predator (Daphnia). In this context, phototaxis would seem maladaptive.
1) State a formal hypothesis for the experiment.
2)What do you predict will happen in the cultures that you are setting up?
please help!
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