Transcript Muscle tissue Trichinella juvenile

•18.8 Nematodes have a pseudocoelom and a
complete digestive tract
– Nematodes (roundworms) make up the phylum
Nematoda
• Have a pseudocoelom and a complete digestive
tract
• Are covered by a protective cuticle
• Are numerous, diverse, and found in most
environments
– Many are free living; others are plant or animal
parasites
LE 18-08a
Mouth
– Caenorhabditis elegans, a free-living nematode,
is an important organism for genetic research
• The complete genomic sequence has been
determined
– Trichinosis is a disease caused by the
nematode Trichinella spiralis
• Humans can get this parasite by eating raw pork
LE 18-08b
Muscle tissue
Trichinella juvenile
• 18.9 Diverse molluscs are variations on a
common body plan
– Molluscs have bilateral symmetry, a complete
digestive tract, a coelom, a circulatory system,
and generally separate sexes
– General body plan of a mollusc
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Muscular foot
Visceral mass containing most internal organs
Mantle
Rasping radula in many
• 18.9 Diverse molluscs are variations on a
common body plan Phylum Mollusca
– Molluscs have bilateral symmetry, a complete
digestive tract, a coelom, a circulatory system,
and generally separate sexes
– General body plan of a mollusc
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•
Muscular foot
Visceral mass containing most internal organs
Mantle
Rasping radula in many
Gastropods (“belly foot”) are the largest group of
molluscs
Snails and slugs
Live in freshwater, saltwater, and terrestrial
environments
Most are protected by a single spiraled shell
Many have a distinct head with eyes at tips of
tentacles
Still on Mollusks…
– Cephalopods (“head foot”) are adapted to be fast,
agile predators
• Include squids and octopuses
• Except for chambered nautilus, shell is small and
internal or missing
• Mouth is at base of foot
• Use beak-like jaws and radula to rip prey
• All have large brains and sophisticated sense organs
• Giant squid is largest of all invertebrates
•18.10 Annelids are segmented worms
– A segmented body resembling a series of fused
rings is the hallmark of phylum Annelida
• Probably evolved as an adaptation facilitating
movement
• Allows for flexibility, mobility, burrowing
– Annelids range from less than 1 mm to 3 m in
length
– Annelids are found in damp soil, the sea, most
freshwater habitats
• Most are bottom-dwelling scavengers