RespirationAquatic annelids often breathe through gills, which exchange gases underwater. Land-dwelling annelids exchange gases through their skin.
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CirculationAnnelids have a closed circulatory system, where blood is contained in blood vessels. In earthworms, blood circulates through two main blood vessels. The dorsal blood vessel acts like a heart, pumping the blood.
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ExcretionAnnelids remove digestive waste through the anus. Ammonia waste is removed by the excretory organs called nephridia.
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Feeding/DigestionAnnelids can be anything from filter feeders to predators. Many use a pharynx to feed, but some have jaws to capture prey. In earthworms,
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Life Cycle/ReproductionMost annelids reproduce sexually. Many annelids are hermaphrodites, but some do have separate sexes.
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Response to StimulusMost annelids have a well developed nervous system, with a brain and several nerve chords. Sensory organs best developed in free-living marine annelids. Many have more complex sensory organs, like chemical receptors and organs that help detect gravity. Many of these worms have two or more eyes.
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MovementAnnelids have two major kinds of body muscles:
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HabitatRag worms like to be in sandy or muddy environments. Earthworms are found in many terrestrial environments like moist, well-vegetated areas.Leeches usually inhabit marshes, rivers and ponds. One fifth of all leeches live in the sea, while certain species live attached to the forest vegetation.
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Distinguishing Features
Annelids have ring-like body segments where most segments are similar to one other, but there may be specialized ones. The body is divided with septa, which are internal walls between each segment. Segments can be specialized for certain functions. They can have one or more pairs of eyes, pairs of antennae, other sense organs, and respiration. In some annelids, bristles called setae are attached to each segment. They have a true coelom, so their body cavity is completed lined by mesoderm. They also have a complete gut.