1. BIG BUGS By john ranelli

2. Hypothesis Modern beetles are must smaller than prehistoric beetles because reduced atmospheric oxygen has caused the beetle’s trachea, thus overall body size, to have a smaller growth capacity.

3. What is an exoskeleton ? An exoskeleton is an external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". example of exoskeleton animals include insects such as grasshoppers Cockroaches crustaceans such as crabs and lobsters. The shells of the various groups of shelled mollusks, including those of snails, clams, tusk shells, chitons and nautilus are also exoskeletons.

4. Role of an exoskeleton Exoskeletons contain rigid and resistant components that fulfill a set of functional roles including protection, sensing, support, feeding and acting as a barrier against desiccation in terrestrial organisms. Exoskeletons have a role in defense from pests and predators, support, and in providing an attachment framework for the muscles

5. Growth in an exoskeleton Since exoskeletons are rigid, they present some limits to growth. Some organisms grow by adding new material to the aperture of their shell, as is the case in snails, but many arthropods must moult their shell when they outgrow it, producing a replacement