A. He should add shells that are different colors, but the same size and type, to the tank and observe which shells the hermit crabs choose.
Durning an experiment you need to keep everything the same but only change the certain things based on your theory.
Such as how the student wanted to see if the color attracted the crab. If he had changed the size and type of the shell then the crab would have chosen the bigger one as they tend to grow into larger shells.
One big place and they will one big population
A person with darker skin produces more melanin. Those are the dark brown pigments that come from your skin, hair, or eye color.
Hope that helps. -UF aka Nadia
Single seismograph can register the occurrence of an earthquake. Analysis of the waves can yield the distance between the sensor and the epicenter. This describes a circle with the seismograph at the center. ... Adding data from a third station pinpoints the epicenter as the only place where all three circles intersect