Overview of Phylum Platyhelminthes (Flatworms)

Bilateral symmetry

The type of symmetry flatworms have.

Organ level

The level of organization in flatworms, indicating they have true organs and organ systems.

Acoelomate

The type of body cavity flatworms have, lacking a body cavity between the digestive tract and body wall.

Incomplete digestive system

A digestive system with only one opening (mouth) and no anus, where digestion occurs in the gastrovascular cavity.

Ladder-type nervous system

The kind of nervous system flatworms have, characterized by paired cerebral ganglia (simple brain) and two longitudinal nerve cords.

Flame cells

Specialized excretory cells in flatworms that function in osmoregulation and waste removal.

Reproduction in flatworms

Most flatworms are hermaphroditic and can reproduce sexually or asexually (e.g., regeneration in Planaria).

Classes of Platyhelminthes

The three main classes are Turbellaria (free-living flatworms like Planaria), Trematoda (parasitic flukes like Fasciola), and Cestoda (parasitic tapeworms like Taenia).

Parasitic adaptations in trematodes and cestodes

Adaptations include loss of digestive system (in cestodes), presence of hooks/suckers, high reproductive capacity, and protective outer coverings.