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Annelida

Annelida. Invertebrate taxon. Annelids. B ilaterally symmetric Coelomates with body cavities Triploblastic They have three different tissue layers The endo -, meso , and ectoderm. Annelids. Embryonic Development Protostomes Cleavage is spiral with fate is determinate (fixed)

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Annelida

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  1. Annelida Invertebrate taxon

  2. Annelids • Bilaterally symmetric • Coelomates with body cavities • Triploblastic • They have three different tissue layers • The endo-, meso, and ectoderm

  3. Annelids • Embryonic Development • Protostomes • Cleavage is spiral with fate is determinate (fixed) • Blastopore becomes mouth • Mesoderm arises from cells near the blastopore, with splitting forming the coelom • Cephalization • Cell concentration is in anterior portion and resembles a primitive brain.

  4. Digestive System • consists of an unsegmented gut that runs through the middle of the body from the mouth, located on the underside of the head, to the anus, which is on the pygidium. • The gut is separated from the body wall by the body cavity coelom • The segmented compartments of the coelom are usually separated from each other by thin sheets of tissue, called septa, which are perforated by the gut and blood vessels

  5. Nervous system • Typically consists of a primitive brain, or ganglionic mass, located in the head region • Connected by a ring of nerves to a ventral nerve cord that runs the length of the body; • Cord gives rise to lateral nerves and ganglia in each segment. • Sense organs of annelids generally include eyes, taste buds, tactile tentacles, and organs of equilibrium called statocysts.

  6. Excretory System • In each segment (metamere) of annalida there are a pair of complete excretory structures called metanephridium • The metanephridium has an extremity, the nephrostoma, which collects residuals from the coelom, filtering them and causing reabsorption along its extension. • The things that need to be excreted goes out through a pore, the nephridiopore, which opens in the body surface.

  7. Circulatory System • The blood usually contains hemoglobin • some annelids have a green oxygen-carrying pigment and others have unpigmented blood. • Circulatory system is usually closed, i.e., confined within well-developed blood vessels • In some polychaetes and leeches the circulatory system is partly open, with blood and coelomic fluid mixing directly in the sinuses of the body cavity. • Blood flows toward the head through a contractile vessel above the gut and returns to the terminal region through vessels below the gut and is distributed to each body compartment by lateral vessels. • Some of the lateral vessels are contractile and serve as hearts, i.e., pumping organs for driving the blood.

  8. Life Cycle • Asexual ( All varies on type of annelida) • Annelids can split into two and two adult worms are formed. • A smaller version of an adult annelid can bud from a grown one and grow naturally bigger over time • Annelid can be injured and smaller versions can regenerate and grow from the segments

  9. Life Cycle • Sexual • separate sexes, which released ova and sperm into the water via their nephridia. • fertilized eggs develop into trochophore larvae, which live as planktonand latersink to the sea-floor and metamorphose into miniature adults • In some they use similar external fertilization but produce yolk-rich eggs, which reduce the time the larva needs to spend among the plankton, or eggs from which miniature adults emerge rather than larvae. • Some rest care for the fertilized eggs until they hatch – some by producing jelly-covered masses of eggs which they tend, some by attaching the eggs to their bodies and a few species by keeping the eggs within their bodies until they hatch. • This all depends on the type of annelid and actually the main life cycles aren’t known because there are just too many species to whose cycles are unknown.

  10. Examples • Earthworms • Rag worms • Leeches • Split into three major classes • Polycheata (marine) • Oligochaeta (earthworms) • Hirudinea (leeches)

  11. Pics

  12. Works Cited • "Annelida: Annelid Characteristics — FactMonster.com." Fact Monster: Online Almanac, Dictionary, Encyclopedia, and Homework Help — FactMonster.com. Pearson Education, May 2009. Web. 08 Apr. 2011. <http://www.factmonster.com/ce6/sci/A0856624.html>. • "Annelida: Annelid Characteristics — Infoplease.com." Infoplease: Encyclopedia, Almanac, Atlas, Biographies, Dictionary, Thesaurus. Free Online Reference, Research & Homework Help. — Infoplease.com. Pearson Education, Aug. 2010. Web. 08 Apr. 2011. <http://www.infoplease.com/ce6/sci/A0856624.html>. • "Annelids - Easy Review." Biology Questions. Biology Questions and Answers, Dec. 2003. Web. 08 Apr. 2011. <http://www.biology-questions-and-answers.com/annelids.html>. • Michael, Gregory. "Embryonic Development." Flatworms, Mollusks, Annelids. 18 Apr. 2006. Web. 8 Apr. 2011. <http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20102/bio%20102%20lectures/animal%20diversity/protostomes/lophotrochozoans/lophotrochozoans.htm>. • "Phylum Annelida." University of Minnesota Duluth Welcomes You. University of Minnesota Duluth, June 2002. Web. 08 Apr. 2011. <http://www.d.umn.edu/biology/courses/bio3701/annelida.htm>.

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