Invertebrate Review Questions Answer Key
*Study anatomy of earthworm, grasshopper, squid, sea star
Animals:
1. Give four characteristics most animals have.
Heterotrophic (cannot make own food).
Multicellular (allows for tissues and organ systems).
2.
Eukaryotic (but no cell wall).
Most are motile. (a few are sessile most of their lives.)
Give two characteristics of Invertebrate animals.
a. No backbone (no internal skeleton)
b. Other characteristics vary depending on Phylum  Examples:
i. Many are small and slow moving.
ii. Arthropods = exoskeleton, jointed appendages.
iii. Cniderians = Regeneration of new parts
iv. Molluscs = have a mantle and specialized nervous system. Etc. look in notes.
3. Which animals have an endoskeleton?
a. Echinodermata, Porifera, Cnideria and some molluscs have residual ones.
Sponges/Cnidarians:
1. List the three kinds of body symmetry. What kind do sponges have?
a. Bilateral, Radial and Asymmetrical (without).
b. Sponges are asymmetrical.
2. Mature sponges live attached to one spot, this is referred to as being ___________.
a. Sessile
3. What structures provide support to sponges?
a. Spicules (small “skeletal” parts)
4. Name two body forms of sponges.
a. Sessile and larval
(THIS QUESTION SHOULD READ: Name two body forms of cnidarians)
b. ANSWER: Polyp and medusa
Worms: (Platyhelminthes, Nematoda, Annelida)
1. What type of symmetry do flatworms have?
a. Bilateral symmetry (all worms have this type of symmetry)
2. Where are roundworms found?
a. In human intestines, lymphatic system or other various organs, in pork (muscles), in
sandboxes/soil (Depending on the species of worm).
3. List some parasitic roundworms that infect humans.
a. Trichina (Cause Trichinosis), Filaria (cause Elephantiasis), Pinworms (cause itchy bum),
Hookworms (cause heartworm)
4. Which type of worms have a complete digestive tract with both mouth and an anus?
a. Nematoda and Annelida  Complete digestive system 
5. List two similarities and two differences between roundworms and flatworms.
Similarities
Differences
 Both have bilateral
 Roundworms have a complete digestive system (tube within a
symmetry
tube)
 No body segmentation
 Flatworms do not  flame cells or a mouth/anus.
 Can be free-living or
 Roundworms have more room for organs, more space within
parasitic
their bodies.
 Can infect humans
 Flatworms are acoelomates
 No specialized circulatory
 Flatworms have 2 nerve cords  can regenerate their heads.
or respiratory systems
 Nematodes  anterior bundle of nerves (not a true brain)
6.
What causes the severe inflammation when Filaria attacks a human?
a. Filaria causes Elephantiasis. The worm blocks the lymph vessels in the body and causes
swelling of appendages and sometimes organs. The area becomes abnormally large and
damages the tissues.
7. Describe three features in an Earthworm that would indicate it is more advanced than a nematode.
a. They have a true coelom, this allows for more complex body systems, organs.
b. They have a complete digestive system,
c. They have primitive kidneys for filtering blood and a circulatory system (5 hearts for pumping
blood)
d. They have a more advanced brain than other worms.
Mollusca:
quill
1. Name an organism found from each of the three major classes of mollusks.
mantle
a. Bivalvia  clams, oysters, mussels
b. Gastropoda  snails
gut
c. Cephalopoda  Squid, octopus
anus
2. Where are molluscs found?
gills
a. Most in marine habitats, some in freshwater,
eye
a few snails on land.
Incurrent siphon
3. Sketch a squid (cephalopod) and
label its unique features.
mouth
arm
4.
Describe how gas exchange occurs in an aquatic snail, does it have an open or closed
circulatory system?
s
a. Aquatic snails: Oxygenated water enters through incurrent siphon. Passes through gills to
oxygenate blood. CO2 out excurrent siphon.
b. Open circulatory system: blood vessels empty into open spaces called sinuses where organs
are (i.e. Blood is not contained at all times).
c. Heart pumps Oxygenated blood through blood vessels which ten empties into sinuses and
bathes tissues. De-O2 blood drains from sinuses back through blood vessels to gills.
5. What are chromatophores? Why are they important for some molluscs?
 They are special pigment containing cells that have the ability to reflect light.
 They are responsible for creating eye-colour and skin-colour in cold-blooded animals.
 They are important for some species (ie. Squids and octopi) for camouflage. They can rapidly
change colour by relocating the pigments as well as the special reflective plates within
chromatophores to allow them to blend in with their surroundings.
Echinodermata:
1. Why is the water vascular system important to seastars? How does it work?
a. How echinoderms move and capture food.
b. Water enters in through Madreporite (on the top). Thousands of tube-feet fill with sea water.
Move foot by expanding it, muscles retract them. Tube feet rip open mussels, clams, oysters.
2. How do echinoderms regenerate asexually?
a. By regeneration of missing arms. They can grow an arm back if they lose it. They can also
detach an arm as a survival mechanism. If a predator is eating that arm they will detach it and
attempt to escape.
b. They are capable of regenerating even one arm into a whole new body. This is only possible if
the arm includes part of the central disc. If you cut off only the tip of an arm, the cut off tip will
not regenerate a whole new body, but the animal will grow another arm.
Arthropoda:
1. Compare the breathing of grasshoppers and crayfish.
Respiratory Grasshopper
Crayfish
organ
Spiracles: holes in exoskeleton
Gills: feathery structures that
allow for diffusion of gases.
allow gas exchange in water.
2.
Compare the excretory system of a grasshopper to a crayfish.
Excretory
Grasshopper
Crayfish
organ
Malpighian Tubules
Green Glands
3.
Name the five major classes of phylum arthropoda.
a. Class insecta
b. Class arachnids
c. Class crustacea
d. Class Diplopoda
e. Class Chilopoda
What do all crustaceans have in common?
a. Two body regions.
b. Two pair of antennae.
c. Open circulatory system.
d. 5 or more pairs of legs.
What are the two major body regions of the crayfish or spider?
a. Cephalothorax and abdomen
What are two visible exterior differences between insects and crustaceans?
a. Insects have three body regions (head, thorax, abodomen) whereas crustaceans have only two.
b. Insects have 3 pairs of legs, crustaceans have 5 or more pairs of legs.
c. Many insects have wings, crustaceans do not.
Explain the steps of incomplete metamorphosis vs. complete metamorphosis.
Incomplete
Complete
4.
5.
6.
7.
The nymph more or less resembles the adult. There is
no pupa formed.
Larvae and adults are very different. Pupa
formed.