Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ch. 27.3 Found everywhere Soil, sea, parasites Can look like flat or round worms Actually, more related to clams or octopi! (Share a larval stage) What is an Annelid? Phylum: ANNELIDA; means ‘little ring’ SEGMENTED Separated by SEPTA internal walls between each segment Some segments carry sense organs Annelids have SETAE (bristles) on each segment Contain a true COELEM lined with a mesoderm Tube within a tube digestive tract (mouth anus) Form and Function in Annelids Feeding and digestion: filter feeders or predators Use a pharynx Can use mucus to break down decaying materials Filter feeders Crop and gizzard in earthworms (crop stores; gizzard grinds it up) Circulation Closed circulatory system blood contained in a network of blood vessels Blood circulates in 2 major blood vessels (head to tail). Blood in the dorsal end (top) goes TOWARD the head Blood in the ventral end (bottom) goes TOWARD the tail Smaller blood vessels appear in each segment and supply blood to internal organs Dorsal blood vessel functions like a heart, contracts rhythmically Respiration Aquatic annelids have GILLS Land annelids have gas exchange via moist skin Secrete a thin protective coating of mucus Excretion Produce 2 kinds of waste Passes out via anus Cellular waste that has nitrogen is eliminated by NEPHRIDIA (filter) Response Well developed nervous system consisting of a brain and several nerve cords Marine annelids have other adaptations (sensory tentacles, chemical receptors, gravity sensors, eyes) Movement Body muscles part of the hydrostatic skeleton Longitudinal muscles run from front of worm to the rear; contraction Circular muscles wrap around each body segment; contract to make worm longer and thinner Alternate contracting Reproduction Most reproduce sexually External fertilization Separate sexes Some are hermaphrodites CLITELLUM thickened, specialized segments secrete mucus rings into which sperm and eggs are released (forms a protective cocoon) Groups of Annelids Oligochaetes earthworms; streamlined bodies and few setae Live in fresh water or soil Leeches tropical areas; moist habitats External parasites carnivores Polychaetes sandworms, bloodworms Marine Paired, paddlelike appendages