BIOL 205 - Comparative Invertebrate
Zoology midterm 2 review (midterm exam
tips) University of British Columbia,
Okanagan Campus
,rhynchocoel - --a tubular cavity that holds the introverted proboscis of a nemertean worm and
is sometimes considered homologous with the coelom
how do nemerteans capture prey? - --To capture its prey, the ribbon worm has a unique
eversible proboscis at the front end of the body that injects a venom into its prey. After
injecting it, the worm waits for the prey to be paralysed before moving in to feed on it.
how might you distinguish a nemertean from a platyhelminth? - --Platyhelminthes:
*acoelomate,
*have ciliated epithelial cells roundworms are pseudocoelomate
*hermaphroditic - mostly sexual, but some asexual reproduction occurs
*often covered in cilia which they use for locomotion and their body size varies greatly from
millimetres to metres
Nematodes:
*longitudinal muscles
*have a cuticle that is shed and many species are microscopic
*gonochoric - they reproduce sexually and generally show sexual dimorphism between genders
*have a cuticle that is shed and many species are microscopic
what is a radula, how does it work? - --a structure of tiny teeth used for scraping food particles
off a surface and drawing them into the mouth
Shell layers (Mollusca) - --nacreous--> innermost layer, makes up most of thickness, made of
calcium carbonate
prismatic--> protein + calcium carbonate layer, creates rings
, peristracum--> outermost layer, tough + made of protein
basic anatomy of molluscs - --two basic body regions
=>head-foot: used for locomotion + contains sensory structures
=>visceral mass (mantle): secretes shell, encloses mantle cavity
=>open circulatory system w/ hemocoels (large open spaces)
=>1 or 2 kidneys(metanephridia): ciliated funnel that filters through excretory tubular system
larval forms of molluscs - --Trochophore (planktonic) larvae: characterized by having a band of
cilia that wraps around the body
Veliger (swimming) larvae: ciliated "mouth" structure called velum
Class Caudofoveata and Class Solenogastres (Phylum Mollusca) - ---worm-like, marine classes
-previously Aplacophora, but likely polyphyletic
Class Monoplacophora (Phylum Mollusca) - ---single-shelled, marine, repeated organs
Class Scaphopoda (Phylum Mollusca) - ---Tusk shells
-Tubular shell open at both ends
-Marine
-Gills absent
-Tentacles & radula present
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