Dating

Phylum: Platyhelminthe

Flatworms

•Planarians, flukes, tapeworms

•Most species are parasitic.

•3 germ layers

•Bilateral symmetry

•Lack of coelom

Habitat

• Found in freshwater or marine environments

• Be careful, though; many platyhelminthes are endoparasites!

Activities

• Hunting• Breathing• Excretion• Movement• Reproducing

– “Penis fencing”

Genealogy

• Most species are polyphyletic (arisen from two independent groups from different ancestral groups).

• In this view, Platyhelminthes belong to Lophotrochozoa• Also comes from sponges and other acoelomates.

– Nervous systems– Cell layers– Body cavity

Specialized Structures

• Cephalized nervous system• No anus; food and waste passes

through the same opening.• Only one body cavity: the gut• Gut is highly branched to spread

nutrients.

Seeking

• Fun-loving, docile partner willing to expend the energy necessary for reproduction