<u>Mollusca:</u> Unsegmented exoskeleton, with no appendixes articulated to them. This skeleton has a calcareous origin.
<u>Arthropoda:</u> Segmented exoskeleton, with different appendixes articulated to them, which develop different functions. This skeleton has a chitinous origin.
Explanation:
Clams are bivalves. Their <u>calcareous</u> exoskeleton has two valves dorsally <u>articulated to each other</u>. They do not articulate with any appendix, although. These animals also have a <em>foot, a small head, and a developed mantle cavity</em>. The valves are convex, oval, and <u>unsegmented</u><u>.</u> They are composed of three layers: periostracum, prismatic, and pearly. En the dorsal portion of each valve, there is a bulge called the umbo, which is the oldest part of the valve. The articulation has some teeth-shaped structures that are intercalated, maintaining the valves together and fixed.
Grasshoppers have a <u>chitinous</u> exoskeletondivided into three principal <u>segments or regions</u> that allow their movement: head, thorax, and abdomen. The head is orientated in such a manner that their feeding apparatus is heading down. Also, the head segment has composed eyes and antennae. The thorax is the medial region of the body. It has three segments: the prothorax, mesothorax, and metathorax. Each of these segments articulates with a pair of legs. Finally, the abdomen is composed of many segments that might reach up to 7 or 11.
When the moths camouflage with their surroundings, they are less likely going to be eaten by their predators. So therefore, more moths are going to want to mate with the darker moths that blend with their surroundings.