Phylum Flatworms
• Body flattened
dorso-ventrally
• Bilateral symmetry
• Muscles are grown together with the skin
• Feeding: blindly ending gut system - one oral
opening (and no anus) -> takes up food, releases
excrement, not too effective
• Breathing: through the skin -> no respiratory,
circulatory organs
• Nervous system: ganglionic (nerve cells are
grouped in ganglia)
• Sensory organs: the eye is able to detect the
direction of the light
• Phylum flatworms contains three classes:
– Class Turbellarians
• free living predators
– Class Trematodes (flukes)
• parasites
• E. g. liver fluke – dangerous to human
– Class Cestodes (tapeworms)
• intestinal parasites: absorb nutrients through
their skin
Phylum Roundworms
• Free living or parasitic
• Gut system has two openings: mouth and anus
Phylum Ringworms (Annelids)
• Segmented animals
• Skin:
– Mucus is exreted: skin-breathing
• Muscles
– Circular
– Longitudinal
• Muscles grown
together with skin
• Bristles: help locomotion
• Locomotion
• Gut system
– Two body openings
• Feeding: predators, saphrophites,
parasites (blood sucking)
• Breathing: by diffusion, through the skin
• Circulatory system (O2, CO2 and nutrient
transport): closed
• Excretory organs: in every segment
• Nervous system:
– Ganglionic: brain, chain of ganglia
• Breeding: might be hermaphroditic, two
worms exchange sperm; egg and sperm
cells meet in the clitellum
• Examples: earthworm, leeches