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Annelida
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Annelida General Info Segmented worms Contains 3 classes –Polychaeta –Oligochaeta –Hirudinea Triploblastic protostomes with a coelom, closed circulatory system, and true segmentation
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Class Polychaeta Called: lugworms, clam worms, bristleworms, fire worms, palolo worms, sea mice, featherduster worms They look the most diverse of the classes of Annelids Some have fine, barbed hairs that will embed in skin if you touch them Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. http://www.ucmp.berkeley.edu/annelida/polyintro.html
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Class Oligochaeta Earthworms Eats its weight in soil each day –Suck in organic and other material by expanding pharynx, grinding up soil in the gizzard Hermaphroditic-they use copulation No eyes because they live underground http://romunov.blogsome.com/images/ol igochaeta.jpg
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Class Hirudinea Leeches Inhabit fresh water for the most part, some tropical Flattened dorsoventrally (like a flatworm) The coelom is not divided, unlike Oligochaeta and Polychaeta. All have evolved suckers on one or both ends, some have evolved the ability to suck blood –Parasitic This is the picture from the Bio Book
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Body Plan 3 body regions-prosomium, trunk, pygidium; head, thin body, small tail Average length 1.36 Bilateral Metameric (segmented) Cylindrical body Have a coelom
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Feeding Wide range Detritus and algae; eat decomposing organic material, small organisms, and soil particles Ingest soil-increases rate of the nutrient cycle Castings-pass out what they don’t need (earthworms) Filter feeders, scavengers Complete digestion, extracellular, have a mouth and anus
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Respiration Not true respiratory organs Diffusion, respiration can occur directly through body walls Cutaneous (occurs due to rich vascularity under epidermis) or branchial Gills if aquatic vascular
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Circulation True closed circulatory system-blood circulates with in blood vessels and through heart May have several hearts First to have closed system, makes pumping more efficient Blood usually contains hemoglobin
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Excretion Use nephridia: coiled tubules with an expanded funnel- shaped nephrostome for excretion The nephrostome is attached to the septum dividing two segments and opens into the anterior segment. The tubule opens to the outside. Filtration of the blood across the tubule wall occur through diffusion Most annelids have metanephridia which depend on filter cells to filter blood twice Primitive annelids have protonephridia which perform two filtrations Aquatic annelids excrete ammonia terrestrial annelids excrete urea
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http://infusion.allconet.org/webquest/annelida.html
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Response Simple brain located in the anterior end Ganglia: nerve cell bodies, located in every segment One ventral nerve cord runs the length of the body connecting to the brain and paired ganglia of each segment Sense light, moisture, chemicals, and physical stimulation Some have eyes (polychaeta)
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http://tolweb.org/articles/?article_id=57
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Movement Hydrostatic skeleton-flexibility Annelids contract various muscle groups around the segment that elongate one segment at a time. Then they contract muscles along the length to move forward Terrestrial annelids have setae: chitin that help anchor them to the ground Movement: –crawl using parapodia- outgrowths that look like bristles (lugworms) –Swim (leeches) –Crawl by folding segments (like earthworms)
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Reproduction Asexual Reproduction: –Budding: an outgrowth of the parent separates to form a new individual (not similar size) –Fission: parent separates into two or more individuals of equal size Sexual Reproduction (following slides)
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Polychaeta Sexual Reproduction External fertilization in water Lack gonads Result in ciliated trochophore larvae Swarming occurs in some species- individuals join together to release sperm and/or eggs
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Oligochaeta Sexual Reproduction Hermaphroditic reproduce sexually by reciprocal fertilization where partners exchange sperm by joining their anterior ends during mating After mating, the oligochaeta produces cocoons that take up eggs which are then fertilized by the sperm Young worms hatch from cocoon (no larvae)
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http://image.tutorvista.com/content/diversity-living-world/earthworm-structure.jpeg
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Works Cited "All Tropical Fish - Bristleworms Class: Polychaeta." All Tropical Fish - Marine Fish, Corals, Invertebrates and Freshwater Fish. Web. 20 Apr. 2010.. "The Annelids (Phylum Annelida)." The Earth Life Web. Web. 20 Apr. 2010.. “Annelids-Easy Review.” Biology Questions. Web. 19 Apr. 2010.. “Annelida-Worms and Leeches.” CSIRO Entomology Home. Web. 19 Apr. 2010.. "Introduction to the Polychaeta." UCMP - University of California Museum of Paleontology. Web. 20 Apr. 2010. Ramel, Gordon. “The Annelids (Phylum Annelida).” The Earth Life Web. Web. 19 Apr. 2010.. Raven, Peter, and George Johnson. Biology. 6. New York, New York: McGraw-Hill, 2002. 906-909. Print. Rouse, Greg W., Fredrik Leijel, and Damhnait McHugh. 2002. Annelida..
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