Invertebrates Double Jeopardy
Annelids
Mollusks
Arthropods
Echinoderms
Diagrams
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Compliments of the James Madison Center, JMU
What features distinguish
annelids from roundworms?
Unlike roundworms, annelids have
segmented bodies and a true coelom that
is lined with mesoderm.
List the defining characteristic
for each class of annelid.
Oligochaetes typically have fewer setae
than polychaetes and live in soil or fresh
water. Leeches are typically external
parasites that suck the blood and body
fluids of their host. Polychaetes are
marine annelids that have paired,
paddlelike appendages tipped with setae.
Describe the feeding strategies
of earthworms and leeches.
Earthworms use their pharynxes to suck
soil and detritus into their esophagus.
Leeches suck the blood and body fluids of
their host.
How do roundworms excrete
digestive waste and cellular
wastes?
Digestive waste passes out the anus at
the end of the digestive tract; Cellular
waste containing nitrogen is eliminated by
nephridia, which are excretory organs that
filter fluid in the coelom.
An earthworm has more light-sensitive
cells in its anterior and posterior
segments than in other parts of its body.
Explain how this is advantageous for
the worm.
Having more light-sensitive cells in the
front and back ends is advantageous,
because the animal moves forward and
may be attacked by a predator from the
rear.
What is a mollusk?
A mollusc is a soft-bodied animal that
usually has an internal or external shell.
List and describe the four parts of
the mollusk body plan.
Foot, mantle, shell, visceral mass. The
muscular foot can have different forms,
e.g., spade-shaped; mantle is a thin
tissue layer covering most of the
mollusk’s body; shell, when present,
made of calcium carbonate; visceral mass
is internal organs.
Describe the main
characteristics of the three
major classes of mollusks.
Gastropods – shell-less or one shell,
ventral foot; bivalves – two shells;
cephalopods – head attached to foot.
Why are land snails restricted to
moist environments?
Land snails respire using a mantle cavity
that has a large surface lined with blood
vessels. Because this lining must be kept
moist, it confines land snails to moist
places.
Compare open and closed
circulatory systems. Why are open
circulatory systems found mostly in
small animals that move slowly?
In an open system, blood is pumped through
vessels by a simple heart and works its way
through different sinuses. In a closed system,
blood is circulated through a network of blood
vessels. A closed system supports greater
oxygen needs because blood moves more
quickly through the body.
What are the main
features of arthropods?
Arthropods have a segmented body, a
tough exoskeleton, and jointed
appendages.
Describe the process of
digestion in spiders.
Spiders first inject enzymes to liquefy
their food, then suck the tissues into a
specialized pumping stomach, which
forces the liquid through the rest of the
digestive system.
How is the process of
molting related to growth
in arthropods?
During molting, an arthropod sheds its
entire exoskeleton and manufactures a
larger one to take its place. This process
creates room for growth.
What organs are used in arthropod
respiration? Which are found in
terrestrial arthropods? Aquatic
arthropods?
Most terrestrial arthropods breathe
through tracheal tubes. Other terrestrial
arthropods respires using book lungs.
Most aquatic arthropods respire through
featherlike gills. The horseshoe crab
respires through organs called book gills.
How do the three largest
groups of arthropods differ?
Crustaceans: two pairs of branched
antennae, two or three body sections, and
chewing mouthparts called mandibles;
Chelicerates: have mouthparts called
chelicerae and two body sections, and nearly
all have four pairs of walking legs;
Uniramians: jaws, one pair of antennae, and
unbranched appendages.
What is an echinoderm?
An echinoderm has a spiny skin, an
internal skeleton, and a water vascular
system with tube feet. Most have fivepart radial symmetry.
What is the water vascular system?
How is it important to echinoderms?
The water vascular system is a system of
internal tubes. The system carries out
respiration, circulation, and movement.
List the major classes of
echinoderms and describe their
characteristics.
Sea urchins and sand dollars have plates that form
a box around their internal organs. Brittle stars
have long, flexible arms and can move quickly.
Sea cucumbers look like cucumbers. Sea stars
move by creeping slowly and can repair
themselves when damaged. Sea lilies and feather
stars have a stalk by which they attach to the
ocean floor.
Echinoderms are
deuterostomes. What does
this indicate about their
relationship to other animals?
Echinoderms are more closely related to
chordates than to other invertebrates,
most of which are protostomes.
Why is tearing a sea star apart and
throwing it back into the water an
ineffective way of trying to
reduce sea star populations?
If a sea star is pulled into pieces, each
piece will usually grow into a new animal.
Label the following:
Insert Text for Question
Category 5 – 40 points
Insert Text for Question
Category 5 – 60 points
Antennae
Compound Eye
Mouth
Palps
Spiracles
Abdomen
Thorax
Head
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Category 5 – 100 points