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Flatworms/Roundworms. Phylum Platyhelminthes platy-flat, helminth-worm three classes 1. Class Turbellaria 2. Class Cestoda 3. Class Trematoda Bilateral symmetry Non-segmented no respiratory or circulatory systems: depend on diffusion to transport nutrients.
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Flatworms/Roundworms • Phylum Platyhelminthes • platy-flat, helminth-worm • three classes 1. Class Turbellaria 2. Class Cestoda 3. Class Trematoda • Bilateral symmetry • Non-segmented • no respiratory or circulatory systems: depend on diffusion to transport nutrients. • Sense receptors and nerves found at the anterior end • Free living or parasitic • Found n rivers, lakes, and streams
Class Turbellaria: Flatworms a. free living b. posterior end tapers, anterior end is spade-shaped c. movement 1. swimming: muscle cells controlled by nervous system allow to twist and turn d. Feeding 1. scavengers 2. feed on protozoans 3. in the middle of their body, they have a small opening called a mouth. A muscular tube called a pharynx, located behind the mouth extends out of the mouth and sucks in the food. The food is passed into the intestine. Nutrients are absorbed by the intestinal wall through diffusion. Any waste or undigested food are excreted through the pharynx and out through the mouth. 4. Flame cells: located on the ends of the branches of the intestines. Excess water are excreted through these cells.
e. Nervous control 1. Eyespots: located on the anterior end of the body. Sense light 2. Ganglia: a cluster of nerve cells located on the anterior end of the body. Extending from the ganglia are two cords running the length of the body, Sense: touch, taste, and smell f. Reproduction 1. Sexual: Hermaphrodites a. no self-fertilization b. fertilize each other at the same time: worms join, one worm delivers sperm to another while receiving sperm from its partner at the same time. 2. Asexual a. Regeneration. They attach themselves and stretch until they split in half. Each half regenerates.
g. Basic Structure: 1. gastrovascular cavity 2. pharynx 3. mouth 4. ganglia 5. Flame Cells 6. Two nerve cords 7. eyespots 8. anterior 9. posterior 10. Intestines http://dragon.seowon.ac.kr/~bioedu/bio/ohp/t-162.jpg
Class Cestoda: Flatworms • Parasitic flatworms: tapeworms • They have a head called a scolex suckers and hooks that allows them to attach themselves to their host • Attach to intestinal walls • Food is absorbed through skin of parasite • Reproduce: proglotidds: rectangular body sections. They are reproductive units that are added throughout the worms life. A proglottid can have up to 10,000 eggs. • There are more than 5,000 species of tapeworms known to science, and nearly every species of vertebrate is liable to infection from at least one species of tapeworm.
Class Trematoda: Flatworms • Largest class • Parasitic worms called flukes • Endoparasitic: live inside the host • Ectoparasitic: live outside the host • Have one or more suckers to attach to host. Use pharynx to suck body’s fluids for food. • Reproduce: can have more than one host. EX: Shistosoma 1. Blood fluke responsible for shistosomiasis: found in tropics 2. People wade in infected water, and parasites bore through skin and make their way to blood vessels. This causes bleeding and of intestinal walls and liver damage. 3. Also includes a special species of a snail as part of their life cycle.
Roundworms • Phylum Nematoda • Bilaterally Symmetry • Found Everywhere. Pets: wormed, soil, humans etc… • They have a body cavity that forms between the gut and the body wall. Food passes into the mouth and is excreted through the anus. • Many nematodes are free living and play critical ecological roles as decomposers and predators on microorganisms. But nematodes also include parasitic species, a number of which affect humans directly or indirectly through their domestic animals. These include the common roundworms, which probably infest more than half the world's humans; hookworms; trichina, the worms that cause trichinosis and Ascaris worms; pinworms, another extremely common parasite, even in the United States, which can be transmitted from human to human by eggs floating in household dust; and filarial worms, primarily tropical parasites that cause diseases such as filariasis (elephantiasis) and onchocerciasis (river blindness).
Trichinella Ascaris A cluster of nematodes, the roundworm of dogs, Toxocara canis.
