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 hostHas all three layers (endoderm,

mesoderm, ectoderm)Acoelomate – no body cavity.

An Important Group

 Many nasty parasitic infections.

DugesiaTapeworms

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.