Evolutionary Adaptations of Worms

Body and Shape

• While some worms possess muscles with which they can move themselves, others rely upon elements of their environment -- wind, water and host creatures -- to move them from place to place. Though several creature types commonly referred to as worms -- such as blindworms -- have backbones, proper worms do not. The main evolutionary adaptation of worms related to their body and shape is their long, roughly cylindrical bodies that are perfectly suited for wiggling or burrowing through tight environments.

Senses

• As their primary environments tend to be tight, closed environments with little light or sound, many oligochaetologists maintain that worms do not possess the sense of sight or hearing. While some suggest that worms rely entirely on a sense of touch, others maintain that worms also have a heightened sense of smell, which allows them to navigate their environment. Regardless of whether or not they possess a sense of smell, a worm's sense of touch is an evolutionary adaptation that allows it to sense things like increased moisture, approaching predators and temperature changes.

Digestive System

• Worms' digestive systems take up the majority of the space inside of them. The system starts with the worm's mouth, which is positioned at the front-facing end of the worm. While most worms do not have teeth, relying solely on their slow locomotion to force nutrients from earth into their mouths, other worms -- particularly parasitic worms -- have teeth they use to latch onto their food source. Other worms use their pharynx to gather food and bring it into the mouth before coating it with saliva to soften it and start the digest process. The pharynx pushes food into the worm's crop, which acts as a storage compartment for food and other materials that will be digested. The food then travels to the worm's gizzard which, along with small stones the worm ingests, works to break the food down. The gizzard then pushes the fully digested food into the worm's intestines, where digestive juices essentially melt the ground up food materials even further, leeching nutrients for the worm's body. These nutrients feed directly into the worm's blood system, while the byproduct is expelled through the worm's anus at the opposite end from the mouth.

Other Organs

• Because of their long, slender, tubular body, many worms have developed multiple hearts to keep blood pumping to all parts of their body. Additionally, as worms are only capable of propelling themselves forward, they have developed forward-facing reproductive organs. Additionally, various types of earth worms have developed a strong, muscular organ called a clitellum, which aids in propulsion, as well as houses eggs. The clitellum demarcates the worm's "head" from its "tail."