Transcript Phylum Annelida - Net Start Class

Phylum
Annelida
By: Esther Lien
Harlan Cox
Siva Gandu
5th period
Phylum
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General Characteristics
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Annelids are all bilaterally symmetrical animals. They range in size from much less than 1 mm in
length to more than 3 m
Their bodies are divided into segments that may or may not be visible externally
Their body is composed of a series of ring-like segments that are specialized.
In most annelids there are usually two fluid systems, the coelom and the circulatory system, and
both (if present) are involved in the excretion of waste products.
Classes
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CLASS Polychaeta- Bristle worms
CLASS Clitellata- Leeches
CLASS Pogonophora- Beard Worm
CLASS Echiura- Spoon Worm
CLASS Oligochaeta- Earthworms
Body Plan
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Triploblastic
– is a condition of the blastula in which there are three primary germ layers: the
ectoderm, mesoderm, and endoderm
Most remarkable advance is segmentation or metamerism
They have Elongate body which is usually round. For polychaetes and clitellidae,
the head has prostomium and peristomium which have sensory organs and
feeding organs.
Trunk segmentation appears in external annuli, and it is internally separated by
coelomic compartments which are also separated by septae.
Some are homonomous, with body segments mostly similar, others are
heterononmous, with specialized segments
Feeding
http://www.okc.cc.ok.us/biologylabs/Images/Animal_Images/annelida.jpg
• For polychaetes and oligochaetes
– Raptorial
• Prey captured with Head Appendages and then swallowed as a whole
– Deposit
• They ingest the substrate and then they derive the nutrients from it
– Suspension
• They use tentacles or mucus webs to filter nutrients from fluid environment
• Clitellata
– Have a straight gut
• It has specialized organs and accessory organs, but the digestion is extracellular
• Echiura
– They have a coiled gut
• The mouth is by the anus and the gut is long and coiled
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Pogonophora
– Have no known digestive system
http://www.buzzle.com/img/articleImages/267419-2556-7.jpg
Respiration
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They have no true respiratory organs.
Respiratory gas exchange through skin, gills, parapodia.
They secrete moisture from the dorsal pore
The skin has many tiny blood vessels to gather oxygen across the moist film
covering it.
• Since they breathe with their whole body surface, they will suffocate if
their skin becomes dry.
http://coris.noaa.gov/glossary/new_annelid_186.jpg
Circulation
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Their blood is red because it has hemoglobin
Most annelids have closed and well-develop circulation
In certain smaller forms, the circulation is reduced or absent. They have
Coelomic canals that serve as their blood “channels”.http://www.bumblebee.org/invertebrates/images/earthworm1.jpg
The enlarged and heavily muscular vessels at the anterior end serve as the hearts
that pump the blood.
Their blood is carried from dorsal to ventral vessel in the head.
Earthworms have five pulsating blood vessels that help pump blood from the
main dorsal vessel to the main ventral vessel.
http://tolweb.org/tree/ToLimages/circulatory.jpg
Excretion
• Each segment has a pair of nephridia which are long coiled ciliated tubes
to excrete their metabolic wastes.
• Blood and coelomic fluid enter these tubes where nutrients, water and
salts are removed.
• Their waste products are transported out of the body through the coelom
by specialized excretory tubes.
http://johnson.emcs.net/life/images/earthworm.jpg
Response
• The nerve cord has two sorts of fibers: normal and giant nerves
– The nerve cord runs down the whole body .
http://tolweb.org/tree/ToLimages/eyes.jpg
– The giant nerves are only important during rapid escape maneuvers.
• Polychaeta
– Bodies organized into regions according to the function and structures.
– They have a well-developed head with specialized sense organs
• Oligochaeta
– They have no eyes, but they have many photoreceptors, chemoreceptors, and
mechanoreceptors that are concentrated near the ends of their body.
– They have fewer setae than polychaetes and no parapodia or head region.
http://media-2.web.britannica.com/eb-media/37/73337-004-B0D75E62.jpg
• Polychaetes
Movement
– Parapodia, paired, fleshy, paddlelike flaps, used for
swimming, burrowing, or slow crawling.
– Fast crawling is performed by undulating the body.
• Oligochaeta
– Chaetae – tiny hairs that provide anchoring points for
burrowing
– They deform either the whole body, or segments of the
body by contracting the circular and longitudinal muscles
alternately
• Hirudinea
– Swim with snake-like motions
– Use suckers to anchor themselves to objects
– Non-aqueous leeches crawl by extending and contracting
their body
• Polychaetes
Reproduction
– Involves separate sexes and external fertilization, usually in water away from
both parents
– Lack permanent gonads, the gamete producing sex organs
– Gametes are produced from the germ cells in the lining of the coelom or in
the septa
• Oligochaeta
– Hermaphrodites – each worm has both eggs and sperm
– When reproducing sperm goes in both directions to and from each worm
– Fertilized eggs are put in a cocoon that forms over the parent body and then
falls off
• Hirudinea
– Internal fertilization within the female’s body.
– A sperm sac passes over the eggs which are deposited inside
http://image.tuorvista.com/content/di
versity-living-world/earthwormstructure.jpeg
Works Cited
"Annelida." Bumblebee.org. Web. 17 Apr. 2010.
<http://www.bumblebee.org/invertebrates/ANNELIDA.htm>.
Mehaffey, Leathem. "Outline for Annelids." Vassar College. 2001. Web. 17 Apr. 2010.
<http://faculty.vassar.edu/mehaffey/academic/animalstructure/outlines/an
nelida.html>.
Ramel, Gordon. "The Annelids (Phylum Annelida)." The Earth Life Web. Web. 15
Apr. 2010. <http://www.earthlife.net/inverts/annelida.html>.
Raven, Peter H., and Peter H. Raven. Biology. 6th ed. New York: McGraw-Hill, Higher
Education, 2002. 906-09. Print.
Rouse, Greg W. "Characteristics of Annelida." Tree of Life Web Project. 2002. Web. 16
Apr. 2010. <http://tolweb.org/articles/?article_id=57>.