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Phylum Annelida
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Segmented Worms
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What are the two other phyla of worms
that we just learned, one was on your test?
Unit 7 Worms 3 Slide Recap!
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Platyhelminthes
Recap!
Flat worms (12,000 species)
Things you should know:
o
What kind of symmetry?
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What was the term for having a
defined head?
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How many layers of tissues,
and what are they?
Things you might know:
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They are typically flattened
dorso-ventrally (thin from front
to back).
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They sometimes contain a gut
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They are acoelomate (no body
cavity).
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They have distinct organs and
organ systems (e.g., digestive,
nervous, reproductive, etc.
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They DO NOT have a
circulatory system!
o
It has the following classes:
cestoda (tape worms),
trematoda (flukes), monogea
(flukes), turbellaria (planarians)
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Nematoda Recap!
Round worms
(90,000 described species, though
probably many more exist)
Things you should/might know:
o
What would the cross section
of this worm look like?
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They differ from Flatworms in
regards to body cavity how?
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They do not have cilia, but
have a thick cuticle. Together
with pseudocoelom (which
o
provides a hydrostatic
skeleton) provides a skeleton
for the worm.
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They have a complete
digestive tract. (mouth -> anus)
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They only have longitudinal
muscles. Therefore move by
“thrashing” or “whipping”
around
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Still they DO NOT have a
circulatory system 
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There are about 12,000 species
an old theory says they gave rise to the arthropods. More
recent information seems to contradict this, though.
earthworms and leeches probably best known examples.
Segmented WormsPhylum Annelida
Major Characteristics!
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They have a true coelom,
though partitioned by septa
(septa are incomplete in
polychaetes).
They have a digestive tract,
blood vessels, nerve cords run
the length of the animal
They have “heart” (actually
pumping blood vessels) and
blood vessels present
(earthworms respire through
skin-closed system), SO THEY
DO HAVE A CIRCULATORY
SYSTEM
They have metanephridia (a
primitive kidney)
They also brain-like ganglia
(biological tissue)
They are hermaphroditic, but
cross fertilize (clitellum is
reproductive organ).
They have a variety of muscles circular, longitudinal, others.
They have a hydrostatic
skeleton (coelom+muscles)
Phylum Annelida has
3 classes:
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Polychaetes
Oligochaeta
Hirudinea
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They contain parapodia - “pair” of lobes (paddles) with setae
(stiff hair like projections used for traction) that help worm
move.
These parapodia are also vascularized (i.e., supplied with lots
of blood vessels) for respiration.
Contain no permanent gonads.
They feed in many different ways
Mostly marine.
Polychaetes
Earthworms:
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Oligochaeta
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They live in soil and fresh
water.
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They only have a few setae per
segment, and no parapodia
(un-jointed lateral outgrowths
that bear the chaetae)
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The clitellum (glandular, nonsegmented section near the
head) is used for mating (line
up and transfer sperm across
clitellum).
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They feed on soil nutrients and
decaying vegetation.
Important in keeping soil
aerated.
Leeches:
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o
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Hirudinea
They have no setae
They still have a clitellum
They have suckers front
and back (for locomotion)
They have raptorial or
parasitic (have anticoagulant in saliva)
They are not very
segmented internally - lots
of connective tissues
instead.
some are again being used
in medicine to help
alleviate tissue swelling
(anti-coagulants).
Now for a quick activity…
Please make it so that your
table has exactly 3 people
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You will be given three worm cookies in cups, when I
say go you are to place the worm cookies in their
correct phyla. The cookies should be ordered from left
to right in the following order:
Platyhelminthes/Nematoda/Annelida
The winning group will get a Free HW pass (Which
cannot be used on any part of the Research Project)
Now since we are worm
experts…