The researchers collected periwinkles and crabs from sites in the northern and southern parts of the Gulf. A single crab was placed in a cage with eight periwinkles of different sizes. (All crabs were of similar size and included equal numbers of males and females.) Four treatments were set up, and each treatment was tested 12 to 14 times:
Northern crab caged with northern periwinkles
Northern crab caged with southern periwinkles
Southern crab caged with northern periwinkles
Southern crab caged with southern periwinkles
After three days, the researchers assessed the fate of the eight periwinkles. The bar graph shows the data from this experiment.
In a second experiment, the researchers removed the bodies of northern and southern periwinkles from their shells and presented the bodies to northern and southern crabs. The crabs consumed all of the unshelled periwinkles in less than an hour.
Which of the following is a hypothesis the researchers were testing in this study?1. Through evolution, periwinkle populations without a history of predation by crabs have become less vulnerable to crab predation.
2. Through evolution, all periwinkle populations have become less vulnerable to crab predation.
3. Through evolution, periwinkle populations with a history of predation by crabs have become more vulnerable to crab predation.
4. Through evolution, periwinkle populations with a history of predation by crabs have become less vulnerable to crab predation.