ASCHELMINTHES ( ROUND WORMS). Roundworms are large groups of 12,000 species . Ascheli: Round; Minthes: Worm . 8-10 SPECIAL FEATURES. H eterotrophic animals . 2. Circular brain and several longitudinal nerve cords. 3. Respiratory and circulatory systems are absent .
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ASCHELMINTHES (ROUND WORMS) Roundworms are large groups of 12,000 species. Ascheli: Round; Minthes: Worm Valentina Cross 9A
8-10 SPECIAL FEATURES Heterotrophic animals. 2. Circular brain and several longitudinal nerve cords. 3. Respiratory and circulatory systems are absent. 4. They have a complete alimentary canal. 5. Nitrogenous waste is collected by two lateral canals through an excretory pore. 6. Have a complete one way digestive system with a mouth and an anus. 7. Nervous system consists of a nerve ring and many longitudinal nerve cords. 8. Body covered with a tough cuticle. Prevents the parasitic -- being digested free living --from drying out. 9. Separate sexes. The female larger of the pair. Females are capable of producing 100 of thousands of eggs per day. The male usually dies after copulation. Valentina Cross 9A
FIRST FOSSIL • Not many fossil records • Earliest fossils found in Eocene strata (55-38 MYA) • Fossils preserved in amber. • But they are too fragmented to explain about their origins Valentina Cross 9A
LIFE CYCLE Eggs Female roundworms lay eggs environment with the host's feces. Larvae An ingested, fertilized roundworm egg host's small intestine intestinal wall. Migration Some roundworm larvae migrate to lungs they mature for 10 days to 2 weeks Larvae ascend into the throat host swallows them. Adult Reach adulthood and start mating 2 to 3 months. Live up to 2 years. Valentina Cross 9A
DIGESTIVE SYSTEM/EATING • Pharynx. • Food is pulled into the mouth by the sucking action of the pharynx. • Food digestive tract broken down and digested. • Water absorbed waste eliminated. • Digestive tube is 1 cell layer thick. • Roundworms eat: • Bacteria • Fungi • Some species are parasites and live on the blood and body fluids of their host. Valentina Cross 9A
BREATHING + RESPIRATION • A roundworm has no formal respiration system. • Breathe through skin. • Don't have lungs -the oxygen diffuses through their skin into bloodstream. • Have no bones, no eyes and no segments. Valentina Cross 9A
SENSORY SYSTEM AND ABILITIES • Simple nervous systems. • They have several ganglia, or groups of nerve cells in the head region • Lack anything that can really be called a brain. • Simple structures of sense organs, these are that detect chemicals given off by prey or hosts. • Several nerves extend from the ganglia in the head and run the length of the body transmit sensory information and control movement. • The muscles of roundworms run in strips down the length of their body walls. Valentina Cross 9A