Invertebrates_II[1]

Invertebrates_II[1] - Next- Segmented Worms (Phylum...

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Next- Segmented Worms (Phylum Annelida)
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Characteristics of the Annelida • Compartmentalized organization. Body partitioned into segments with internal septa. This allows better locomotion. • Schizocoel, metanephridia, muscles, nervous system • Ventral nerve chord, dorsal brain • Closed circulatory system • Chitinous chaetae (setae) produced by skin cells
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The ANNELIDS – segmented worms S egmentation allows independent movement of each part of the body, permitting better burrowing activity and finer control of body movements. Chaetae (setae) help in locomotion
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Class Polychaeta • Large group of marine worms (45,000 species) • Both mobile and sedentary • Many setae • Parapodia on each segment
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Functions of Parapodia • Locomotion • Respiration • Filter feeding
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Errant Polychaetes • Move about freely • Use parapodia for locomotion and respiration • Many are predators • Some can bite
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Fan Worm • Abundant in estuaries along the California coast • Filter feeds with long feather-like parapodia
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Palolo Worm-Strange Group Sex! Spend most of their life in burrows Once a year (Nov. Full Moon) their hind ends (epitokes) containing sperm and eggs break off and swim to the surface Head ends (atokes) regenerate epitokes for nest year Major festivals in the South Pacific celebrate their yearly orgy
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Class Oligochaeta (Earthworms and their relatives) • Burrowers and in fresh water • Fewer setae • No parapodia • Hermaphrodites • Very important soil organisms
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Some earthworms get very big like this giant earthworm from Australia!
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Earthworm Life Cycle Hemaphroditic (male and female organs in same animal) Male parts of each member of a mating pair transfer sperm to the female parts of the other. Fertilized eggs shed in a cocoon from which small worms hatch
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Class Hirudinea (Leeches) Relatives of oligochaetes Adapted for blood-sucking Septa lost Diverticulate gut Looping locomotion Produce anticoagulants (hirudinin) Once used medicinally, some still are!
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Land leeches can be a bother!
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Some of them are movie stars!
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Hirudotherapy Use of leeches for medicinal purposes. Used since medieval times to relieve inflammations and to correct supposed "imbalances of the four humours", Discredited for centuries, Now used to encourage regrowth of blood vessels after surgery to delicate areas such as mucous membranes, particularly in cases where arterial regrowth was successful but venous regrowth was less so.
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Annelida Ecological and human significance Important members of marine and terrestrial food webs. Improve soil fertility Composting Fish bait Medical and pharmacological applications
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The Ecdysozoa (The Strippers!)
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Ecdysozoa • Includes most animal species • Defined by molecular similarities • Tough exoskeleton that must be molted (ecdysis)
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Phylum Nematoda (Nematodes) Most numerous animals on earth. A handful of soil will contain
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This note was uploaded on 09/23/2011 for the course BIOL 240 taught by Professor Staff during the Spring '11 term at S.F. State.

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Invertebrates_II[1] - Next- Segmented Worms (Phylum...

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