Platyhelminthes (Flat Worms)
Flatworms are soft, flattened worms that have tissues and internal organ systems. They are the simplest animals to have three embryonic germ layers, bilateral symmetry and cephalization.
Body Plan:
Respiration, Circulation, and Excretion:
Flat worms rely on diffusion to transport oxygen and nutrients to their internal tissues, and to remove carbon dioxide and other wastes from their bodies. Flame cells are specialized cells that remove excess water and waste like ammonia from the body. Reproduction:
Flat worms are hermaphrodites, both have male and female reproductive organs. Two worms join together and deliver sperm to each other. The eggs are laid in clusters and hatch within weeks. How flat worms reproduce: http://www.youtube.com/watch?v=wn3xluIRh1Y#t=41 |
Feeding:
Flat worms have a digestive cavity with a single opening, where food and waste pass. Near the mouth is a tube called a pharynx. Small invertebrates or the remains of dead animals are taken into the mouth/anus by the pharynx. The stomach does all the digestion and the nutrients move from the gut into the body by diffusion. Response:
Flat worms are able to sense and respond to at least three forms of stimuli. Sense and respond to light: the eyespot can detect light and allows worm to respond. Sense and respond to chemicals in the water. Sense and respond to touch: the auricles on either side of the head region can sense touch and allows worm to respond. Gangli in the head relay messages to sensory organs down the nerve cords to rest of body. Nerve cords control muscles to allow to eat or move. |
Classes of Flat Worms
Class Turbellarians (Turbellarians)
-Free-living flat worms, most live in marine or fresh water.
-Bottom dwellers, living in sand or mud, under stones or shells.
-Can very greatly in color, form and size
Class Trematoda (Flukes)
-Parasitic flatworms.
-Most infect the internal organs of their host.
-Human- grow inside you and release embryose into intestine, also snails when in water
Class Cestoda (Tape Worms)
-Long, flat, segmented, parasitic worms
-Adapted to life inside the intestines of their host
-Has scolex, contains suckers and hooks to attach to intestines
-Proglottids, segmented pieces of the worm
Class Turbellarians (Turbellarians)
-Free-living flat worms, most live in marine or fresh water.
-Bottom dwellers, living in sand or mud, under stones or shells.
-Can very greatly in color, form and size
Class Trematoda (Flukes)
-Parasitic flatworms.
-Most infect the internal organs of their host.
-Human- grow inside you and release embryose into intestine, also snails when in water
Class Cestoda (Tape Worms)
-Long, flat, segmented, parasitic worms
-Adapted to life inside the intestines of their host
-Has scolex, contains suckers and hooks to attach to intestines
-Proglottids, segmented pieces of the worm