Cnidarian Reproduction
Asexually – budding (polyp form)
Sexually –have separate male and
female medusae that produce
gametes that join through external
fertilization to produce polyps.
Flatworms Platyhelminthes
Bilateral Symmetry
Free-living in freshwater or
parasitic in a host
Has all three layers (endoderm,
mesoderm, ectoderm)
Acoelomate – no body cavity.
An Important Group
 Many nasty parasitic infections.
Dugesia
Tapeworms
Flukes
Flatworm Feeding
Free living flatworms are
scavengers.
Parasitic flatworms use specialized
structures (usually with hooks) to
attach to a host.
Respiration & Excretion
Excretion - Flame cells remove
excess water
Respiration - Oxygen diffuses into
body cells directly.
Flatworm Nervous
Systems
First appearance of cephalization.
Primitive brain.
Eyespots
Flatworm Reproduction
Sexually - Hermaphrodites –
internal fertilzation.
Asexually – fission – when damaged,
regenerates new body parts.
Proglottids – found in tapeworms –
each is shed off individually.