Download Part 9 - glenbrook s hs

2. Phylum Cnidaria - Jellyfish, Sea Anemones, Coral, and
Hydras.
• Cnidarians show radial symmetry
• Are carnivores, with
cnidocytes(stinging cells) on their
tentacles.
• Consist of more than 10,000 mostly
marine species
• Have a body plan that is a sac with a
central digestive compartment, the
gastrovascular cavity. This cavity
functions as a mouth and as an anus.
• Two body forms: the sessile polyp
attaches to a substrate, and the freefloating medusa.
Cnidocytes, and Purple Striped Jellyfish
Jellyfish
How a Cnidocyst Stinging Cell Works
3. Phylum Platyhelminthes-Flat Worms-Tapeworms, Flukes,
& Planaria
• Flatworms are the simplest bilateral
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animals.
Range from about 1 millimeter (mm) to
about 20 meters in length.
Live in marine, freshwater, and damp
terrestrial habitats
Include many parasitic species including
flukes and tape worms.
Tapeworms have a ribbon like body which
can be up to 20m long in humans.
Lack a digestive tract, so they absorb
partially digested food from the intestines
of their hosts.
Humans can become infected with
tapeworms by eating undercooked beef.
Watch 4 minute tape of fisherman with a
parasitic friend.
4. Phylum Nematoda-Round Worms
• Roundworms get their common name from the
cylindrical bodies tapered at both ends.
• Roundworms are among the most diverse and
widespread animals
• Roundworms consist of about 90.000 known
species (perhaps 10 times more actually exist).
• Range in length from 1mm to 1 meter,
• Live in most aquatic habitats, in wet soil, and as
parasites in the body fluids and tissues of plants
and animals.
• Exhibit a complete digestive tract with a mouth
and anus.
• Have a body cavity; pseudocoelom.
• Humans host at least 50 parasitic species
including: pinworms, hookworms, and the
parasite which causes trichinosis.
A free-living roundworm
Nematode
5. Phylum Annelida-Segmented Worms- Earthworms,
Polychaetes, & Leeches
Giant Earthworm
Darwin estimated that an
acre of British farmland has
about 50,000 earthworms
which produce about 18 tons
of castings per year.
• Annelids are worms with body segmentation,
the division of the body along its length into a
series of repeated parts.
• Annelids consist of about 15,000 species.
• Range in length from 1mm to 3 meters long.
• Live in the sea, most freshwater habitats, and
damp soil.
• The three major classes of annelids are
earthworms, polychaetes, and leeches.
• Farmers value the earthworm because they eat
their way through the soil, extracting
nutrients, tilling the soil, and producing
castings which improve the texture of the soil.