Scientists have discovered that web-spinning spiders spin different kinds of webs, depending on internal cues. spiders fed a daily diet of flies made a web that was not sticky and was used as a home. starving spiders, on the other hand, spun a web that was very sticky in order to catch prey. this behavior shows how the internal stimulus of affects animal behavior and survival.

Spiders fed a daily diet of flies are full while starving spiders are hungry.

This behavior shows how the internal stimulus of hunger/fullness affects animal behavior and survival.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.