Annelids
Segmented
worms.
Albert Gordon
Jacob Cole
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Jacob Cole
Types
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Oligochaeta:
Earthworms and other
terrestrial worms;
chaetae (chitin bristles),
no parapodia
Polychaeta: Marine
worms that are free or
tube living; parapodia
Hirudinea: Leeches and
other flat annelids with
no chaetae
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Albert Gordon
Jacob Cole
Body Formation
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Annelids are
Coelmates
which means
that they have a
fluid filled
cavity
completely
surrounded by
tissue
In mature form,
annelids are
long with ridged
segments in
their skin.
Range from
1mm to 3m in
length
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Albert Gordon
Body Formation (cont)
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Bilateral Symmetry
Hydrostatic skeleton; supported by septa
between segments
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Nervous System
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Cerebral Ganglia
That’s it. They’re not exactly intellectuals…
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Digestive & Excretory
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Has mouth and anus; a digestive
tract extends along length of worm.
Metanephridia (same neph as in
nephron of the kidneys in humans)
parallel to worm’s digestive tract
filter blood and coelomic fluid.
Waste secreted through
exterior pores
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Albert Gordon
Jacob Cole
Circulatory
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Closed circulatory system
Many hearts
Blood vessels wrap around the digestive tract
in loops
Albert Gordon
Reproductive System
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Cross-fertilizing hermaphrodites
Secrete mucous cocoon in which embryos
develop
Some can also reproduce asexually via
fragmentation
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More Facts
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Earthworms are beneficial to
farmers because castings
(egested materials) are
valuable as a fertilizer and
help recycle soil.
Hirudinea or leeches are still
used in medicine today to
neatly drain blood from
wounds
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Albert Gordon
Jacob Cole
Quiz Questions
1.
Annelids are:
a.
b.
c.
2.
pseudocoelomates
coelomates
acoelomates
Annelids live in all of the following environments
EXCEPT:
a)
b)
c)
d)
seawater
freshwater
damp soil
inside the human body
Jacob Cole
Quiz Questions Continued
Which of the following do NOT have a closed circulatory
system (select all that apply):
3.
a.
b.
c.
d.
4.
Nematoda
Annelida
Cephalopods
Arthropods
Annelids can reproduce by which of the following
processes?
a)
b)
c)
d)
Self-fertilization
Cross-fertilization
Fragmentation
All of the above
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Citations
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All information from Chapters 32 and 33 of
Textbook (Biology 7th Edition, Campbell,
Reese)
The End
Yay!