Invertebrates use their muscles to move. Most invertebrates have the ability to move, but some do not. Once some invertebrates, such as sea sponges, settle in one place, they will not move again to another location, according to Biology 4 Kids. Some invertebrates may move in search of food, but others are stationary and can create their own food.
Invertebrates have a hard outer shell called an exoskeleton. The exoskeleton is filled with and attached to muscles that contract, and when those muscles contract, the invertebrate's joints flex. Animals such as lobsters, some insects, octopus, coral and sea sponges are all examples of invertebrates. Marine invertebrates may use their feet, tube feet or single large muscular foot to crawl along the ocean floor, while others use fins or propulsion to move through the water.
Invertebrates do not have spines or cell walls. Most invertebrates' bodies are organized in a symmetrical method, which means that if a line was drawn down the middle of the organism, the two sides of the organism would be mirror images of each other. Invertebrates such as sponges and coral are not symmetrical. Some have the ability to produce their own food, and some can reproduce sexually.