Distinguishing FeaturesRoundworms are slender, unsegmented worms with bodies that taper at the ends. They have bilateral symmetry. Most are free-living and live in the soil, and many are parasitic. They have a pseudocoelom, meaning that it has a partial coelom. Phylum Nematoda is one of the most numerous phyla.
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HabitatThey are found from the bottom of the deepest ocean to near the tops of the highest mountains, from the tropics to polar regions, and from every conceivable habitat. Nematodes are also found in or on most other types of organisms as parasites: everything from earthworms, insects, molluscs, fish, reptiles birds, mammals to humans.
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Response to StimulusThey have a simple nervous system with several ganglia. Roundworms have several types of sensory organs that can detect chemicals given off by prey or the host.
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Feeding/DigestionMany roundworms are predators that catch and east smaller animals. They use grasping mouth parts and spines to catch prey. Some worms are decomposers that live in the soil.
Roundworms have a complete gut, which means there is one way in and a separate way out. Food that cannot be digested is removed from the body through the anus. |
Life Cycle/ReproductionRoundworms reproduce sexually. They are dioecious, which means that there are two separate sexes: male or female. Parasitic worms have life cycles that require two or three different hosts or several organs within a single host.
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MovementLateral muscles extend from the head to the tail. This allows the worms to move like a snake when in the water, or push soil out of the way when they're in the ground.
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Respiration, Circulation, ExcretionThey exchanges gases and excrete waste through their body walls, like flatworms. There is no internal transport, they rely on simple diffusion.
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Diseases
Trichinosis
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Ascarid Worm
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Hookworm
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C. elegans
- A nematode that lives in rotting vegetation.
- Very important to scientific study, especially with DNA research.