1. KEY CONCEPT Flatworms, mollusks, and annelids belong to closely related phyla.

2. Flatworms are simple bilateral animals.
Flatworms have a solid body and incomplete or absent gut.
They are the most primitive animal with all three tissues
head
pharynx
mouth
sucker
eyespot
reproductive
system
gut cavity

3. There are three classes of flatworms.
Planarians – mostly marine flatworms, not parasites. Most are hermaphrodites.
head
pharynx
mouth
sucker
eyespot
reproductive
system
gut cavity

4. There are three classes of flatworms.
Planarians
Flukes – internal parasites, can use a snail as intermediate host

5. There are three classes of flatworms.
Planarians
Flukes
Tapeworms- need a flea as an intermediate host to infect dogs or humans

6. Mollusks are diverse animals.
Mollusks are bilateral animals with all three tissues (ectoderm, mesoderm, and endoderm) and a complete digestive tract.
A complete digestive tract has two openings: a mouth and an anus.
All animals with a complete digestive tract are deuterostomes or protostomes.

7. Mollusks share at least one of three features.
Radula- scraping part of mouth
Mantle- secretes the shell
Ctenidia- flat “gills” for breathing
intestine
stomach
digestive gland
foot
anus
salivary gland
crop
mouth
radula
mantle
mantle cavity
heart

8. Most mollusks are classified into three (of seven) classes.
gastropods
pelecypods (also called bivalves)
cephalopods

9. Mollusks have a variety of reproductive strategies.
Most strategies involve sexual reproduction.
Some species are hermaphrodites.

10. Annelids have segmented bodies.
Segmentation refers to the repeated sections of an annelid’s body.
The coelom is a fluid-filled space completely surrounded by muscle.
blood vessels
muscle
hearts
brain
mouth
digestive tract
nerve cord
segment

11. There are three groups of annelids.
earthworms
marine worms
leeches