The main difference between the organisms are the uses of the appendage and the size and number of certain bones. The human arm is used for a variety of functions while the lizard's and the cat's are used for walking an climbing, the whale's for swimming, the frog's for support and the bird's and the bat's for flying.
That the stripes make the snails less camouflaged therefore they are more likely to be eaten.<span />
I believe the answer you are looking for is they are all body systems found in the human body, or organ systems.