Sharks and rays are examples of what kind of fishes, members of the class chondrichthyes?

Sharks and rays are examples of members of cartilaginous class of fish of the class Chondrichthyes

Chondrichthyes is a class of fish which is composed of cartilaginous fishes. Their characteristics are: paired nares, scales, skeletons made of cartilage rather than bone, jawed vertebrates with paired fins and hearts in a series of chambers.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

answer; can each be concretely realized in different ways;