Platyhelminthes Emily Azaria Chris Period 5 General Description

Platyhelminthes Emily, Azaria, Chris Period 5

General Description ● ● Phylum- Platyhelminthes contains flatworms Soft, unsegmented, & flat (no more than a few mm thick) Tissues (tripoblastic) & internal organ systems Simplest animals to have: 3 embryonic germ layers, bilateral symmetry, & cephalization ● Do not have coeloms (body cavity) ● Live in fresh or marine water ● Most of their oxygen through diffusion

Symmetry ● ● No body cavity- aceolomates Bilateral symmetry Gastrovascular cavity with one opening Some breath through skin

Feeding ● Parasites- enter body of other organisms, can absorb and consume what the host eats ● 80% are free living ● Turbellaria- carnivores (tiny aquatic invertebrates)

Circulation ● Flatworms take in oxygen and release carbon dioxide ● Flatworms don’t undergo cellular respiration ● Flatworms undergo diffusion to obtain the oxygen they need, and release carbon dioxide they don’t ● This is mostly the reason why they’re flat Central nervous system: the complex of nerve tissues that controls the activities of the body.

Excretion ● The digestive cavity has only one opening for both intake of food and the excretion of it ● As a result the food cannot be processed continuously ● Cilia help move foods to be digested and then excreted through their mouths Pharynx: the membrane-lined cavity behind the nose and mouth, connecting them to the esophagus. Flame cell: a specialized excretory cell- function like a kidney, removing waste materials.

Response ● They have ganglia ● Have a complex structure for detecting and responding to external stimuli ● Have eyespots that can detect changes in the amount of light in their environment ● Have specialized cells that detect external stimuli

Movement ● Free-living ● Uses cilia and muscle cells

Reproduction ● ● ● Most are hermaphrodites Reproduce sexually with internal fertilization Parasitic Commonly reproduce asexually by fission Can reproduce sexually

Respiration ● Gas exchange ● Uses diffusion

Classes of Platyhelminthes 1. Trematoda 2. Turbellaria 3. Cestoda

Trematoda ● Parasites ● Infect animals and humans ● Specialized body (Parasitic life) ● Fasciola hepatica (Liver

Turbellaria ● Free living flatworms ● Most are aquatic ● Some are terrestrial ● Planaria

Cestoda ● Tape worms ● Intestinal parasites ● Proglottid: segment containing complete reproductive system ● Taenia solium (Pork tapeworm)

Works Cited https: //www. shapeoflife. org/video/flatworms-first-hunter https: //excreting 101. weebly. com/platyhelminthes. html

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