9Characteristics Flatworms have bilateral symmetry. They have no true body cavity except for the gut, and are classified as acoelmates.Their organ systems are formed of ectoderm, endoderm, and mesoderm.
10Schistosoma Life Cycle Parasitic flatworms cause schistosoma in humans. -Infection occurs when cercariae penetrate the skin while in the water. -The cercaria loses its tail becoming a schistosomule which moves through various tissues to the veins. -Adults mature in the in the veins surrounding the intestines or bladder, depending on the species. -Females release eggs which move from the veins to the lumen of the intestine or the bladder. The eggs are then passed from the body in the feces or urine.
12More CharacteristicsFlatworms move by waving hair on their skin to propel themselves forward.They also move by contracting their muscles.Flatworm reproduction is hermaphroditic- each individual produces eggs and sperm.When two flatworms mate, they exchange sperm so both become fertilized.
13Specialized Tissues Flatworms have : A sac body plan, meaning they have one opening that functions as both a mouth and an anus.A pharynx, which extends form the underside of the flatworm and sucks up food through the mouthFlame cells that are used for excretion.Amazing regeneration capabilities.
14Specialized FeaturesCephalization (consists of 2 brains called ganglia and nerve cords arranged in a ladder-like configuration).Gastrovascular cavity functions similarly to that of CnidariaPlanarians, in Class Turbellaria, have eyespots that determines the presence and intensity of light.The head (scolex) of the flatworms have hooks and suckers which function as an anchor.
15Different Types of Flatworms Free-living carnivorous planariansParasitic flukes that feed off the blood of other animalsParasitic tapeworms that live inside the digestive tracts of other animals.
16Examples of Flatworms Turbellaria (free-living) Planaria Monogenea (parasitic)
22Specialized Tissues and Coelom They have a simple nervous system that includes a main ventral nerve cord and a smaller dorsal nerve cordThey use diffusion to breatheThey don’t have an circulatory system so the fluid in their body moves nutrients aroundThey are the simplest group to have an complete digestive systemThey also have a three layer cuticle to keep the body from drying outNematoda and Rotifera are Pseudocoelomates. This is when the body cavity is derived from the mesoderm. The tissues are only loosely bound so it is not as organized as an coelomate
23Movement and Reproduction They use hydrostatic skeleton which change liquid pressure in the body changing the bodies shape causing movement.They also use longitudinal muscles to move their bodies side to sideParthenogenesis is when the female can have a growth that separates into an offspringThey also can reproduce sexually
26Interesting factsThey are a major cause important diseases of plants, animals, and humans.Diseases including filariasis, ascariasis, and trichinosisSome live in food products such as beer and vinegar.