Flatworms, Roundworms, and Annelids Review Answers
1. What phyla of animals have a segmented body plan? Annelids
2. How does a complete digestive tract differ from a sac-like digestive tract? (one way vs two way)
A complete digestive tract has two openings and the food travels in one direction. A sac
like digestive tract has one opening and the food travels in two directions.
3. Draw, label and describe a cross section of an acoelomate, a psudocoelomate, and a coelomate
animal.
4. Describe the functions of and name the major structures of a tapeworm (flatworm)
Scolex: the head, for attachment. Proglottids: body segments, contain genetic materials.
5. What are the advantages of a coelom?
Cushions organs, circulates nutrients, keeps organs in their correct places, allows
space for a nervous and circulatory system.
6. What phyla of animals are pseudocoelomate? Roundworms (Nematoda) acoelomate?
Flatworms (Platyhelminthes) coelomate? Earthwomrs (Annelids)
7. Describe the characteristics of the three classes of flatworms. (Refer to your notes)
8. Describe, including hosts, the life cycle of tapeworms and Ascaris.(refer to pages 315 – 317 in
the text book)
9. Describe all of the classes of annelids, focusing on where they live, what they eat, and one
special feature of the class. Refer to the Annelid note. Classes are Oligochaeta (earthworms
living in dirt) Polychaeta (Britsly marine worms living in the sea) and Hirudinea (leeches,
living in freshwater)
10. Sketch an annelid and label all of its parts.
(Refer to the answers for the earthworms worksheet)
11. How is the body plan of annelids different from free living flatworms?
Free living flatworms (which have a two way digestive system made of a simple
gastrovascular cavity with one opening) don’t have as advanced a digestive system as
earthworms (which have a crop and a gizzard and a one way digestive system with two
openings) Also, earthworms have a circulatory system, including a heart, and a true
coelom, while flatworms have no circulatory system and are acoelomate.
12. How are roundworms different from flatworms?
Roundworms are pseudocoelomate, while flatworms are acoelomate. Roundworms have a one
way digestive system and flatworms have a two way digestive system.
13. Name one similarity and one difference between roundworms and annelids
Roundworms are pseudocoelomate while earthworms are coelomate. Earthworms are segmented
while roundworms are not. Both types of worms have a one way digestive system and three cell
layers.
14. Defend the following statement with reference to one specific feature from each phylum:
“annelids are more 'complex' than roundworms, which are more 'advanced' than flatworms.”
Annelids have a crop and gizzard in their digestive system that flatworms and
roundworms don’t have. Earthworms have nephridia to remove cellular waste while
roundworms only have two simple canals for removing waste and flatworms lack any real
structures for this function. Earthworms have two different types of muscles and can
move in many directions while roundworms and flatworms only have one type.
Earthworms have a true circulatory system while roundworms and flatworms do not.
15. Describe the major evolutionary advances seen in flatworms (as compared to sponges and
cnidarians) Skip this question
16. describe the major evolutionary advances seen in roundworms (as compared to sponges,
cnidarians and flatworms) Roundworms have canals for removing cellular waste and a one
way digestive system with both a mouth and an anus. (flatworms don’t)
17. describe the major evolutionary advances seen in annelids (as compared to sponges, cnidarians,
flatworms and roundworms) Refer to question #14’s answer.
1. For the animal groups below, indicate whether or not each system is present, using the words
“no” and “yes” or “primitive”. It the answer is “yes” or “primitive”, briefly describe the
system, using vocabulary you have learned
Body system Free living flatworms Parasitic flatworms
Parasitic
Annelids
roundworms
Yes: longitudinal
muscles
Yes: longitudinal
muscles
Yes: longitudinal and
lateral muscles
circulatory No
No
No
Yes, closed circulatory
system
Respiratory
(O2 and No
CO2)
No
No
No
Some primitive, some
No
Yes: simple one
way system with
phrynx and
intestine
Yes: mouth, pharynx,
esophagus, crop, gizzard,
intestine and anus.
No
Yes: excretory
canals (primitive)
Yes: nephridia
Musculo
skeletal
digestive
Yes: longitudinal
muscles
Primitive two way
gastrovascular cavity
excretory
No
nervous
Primitive nerves
reproductive
Yes, hermaphrodites
Some primitive nerves, Primitive nerve
Yes: simple “brain” and
some no
ring and two nerve ventral nerve cord
cords
Yes: some
hermaphrodites, some
separate sexes
Yes: separate sexes Yes: hermaphrodites
2. Fill in the blank (annelids)
 a fluid filled, mesoderm lined body cavity
 class of annelids, mostly marine, includes bristleworms
Coelom
Polychaeta
 the “lip” of an earthworm
Prostomium (mouth)
 the structure in the digestive system of an earthworm which grinds
food material
Gizzard
 a ciliates funnel and coiled tube which removed metabolic waste from
the blood of the earthworm
Nephridia
 Type of circulatory system where blood only flows in vessels
Closed
 a muscular action that pushes food through the intestine
Peristalsis
 the oxygen carrying molecule found in earthworm blood
Hemoglobin
 the structure which sucks food into the earthworm's mouth cavity
Pharynx
 a free swimming cilliated larva found in polychaetes
Trocophore
 the structure which stores sperm until the eggs are ready to be fertilized Seminal receptacle
 structure used in reproduction of earthworms which produces a
thick mucus
Clitellum
 the digestive organ in worms which stores food before it is passed on
to the gizzard
Crop
 an egg sac produces by the clitellum which protects developing zygotes
 the place in the worm where blood exchanges materials (food, gas waste)
with its surroundings
Cocoon
 class of annelids to which the earthworm belong
Oligochaeta
Coelom
Label the missing parts of each worm
brain
Eyespots
Flatworm
Pharynx
Nerve cord
Gastro
vascular
cavity
mouth
Earthworm
Intestine
Clitellum
gizzard
Crop
Anus
Dorsal blood vessel
Heart
Brain
Esophagus
Ventral blood vessel
Nerve cord
Mouth
Pharynx
Segments
Mouth
Roundworm
Pharynx
Intestine
Gonad
Anus