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Unit 18: Biology Part 1 Page 18 of 60
Segmented (which creates the shell).
Usually, they absorb
Worms (Phylum oxygen from the water
Annalida) using gills.
Segmented worms, the Only mollusks have a
most developed of the structure called a radula.
three, have both a body cavity and Radulae (the plural of radula) are
segments. Their body cavity helps composed mostly of chitin, and can
give them structure—it serves as a be as simple as a structure used to
hydroskeleton. scrape algae off rocks, to the beaks
By “segmented” it’s of octopuses.
meant that they are
divided into repeating Echinoderms (Phylum
units. They can be Echinodermata)
non-parasitic (i.e.
earthworms) or parasitic (i.e.
leeches). Interestingly, the giant Echinoderms,
red leech only eats giant meaning “spiny
earthworms. skin”, are radial
symmetric marine animals. They
Mollusks (Phylum are found at all depths—both
Mollusca) shallow and deep water. They play
important roles in their
If you have ever gone searching ecosystems. Despite appearances,
though tide-pools at the beach, they do not have skeletons. The
you’ve probably seen your fair “spiny skin” is, in fact, skin
share of Mollusks. This is because covering a spiny endoskeleton
mollusks live mainly in the sea (in (internal skeleton).
the intertidal zone), although some
live in freshwater. How do echinoderms move? How
do they feed themselves?
Mussels, scallops snails, oysters Echinoderms have a water
(from which we get pearls!), and vascular system responsible for
clams are only a few examples of gas exchange, movement, and
types of mollusks. The mollusk
body plan generally involves a feeding. This system is an internal
muscular foot for locomotion, a network of fluid-filled canals.
Depending on the species, they
body housing organs, a head with have various ways of getting food
eyes or tentacles, and a mantle
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