FLATWORMS

CHARACTERISTICs

• Have no body cavity.
• No specialized circulatory and respiratory organs.
• Oxygen and nutrients pass by diffusion.
• Ingestion and egestion just use one cavity.

THEY ARE DIVIDED INTO

THREE ENTIRELY PARASITIC GROUPS

• Cestoda
• Trematoda
• Monogenea

FREE-LIVING FLATWORMS

• Are mostly predators.
• Live in water or shaded humid terrestrial environment.

CHARACTERISTICS

• Don't have internal cavity.
• Regarded as a primitive stage in the evolution of bilaterians.
• Separated out one subgroup. Acoelomorpha.

ROUNDWORMS

CHARACTERISTICS

• Have tubular digestive systems.
• Digestive system has openings at both ends.
• Have successfully adapted to every ecosystem.
• Adapted to: marine water, fresh water
• Soils, polar regions, tropics, highest and lowest elevations.

THEY ARE TIPICALLY LESS THAN

REPRODUCTION

MALES ARE SMALLER THAN FEMALE

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