Reproduction Most Flatworms example essay topic

NOTESCharacteristicsFlatworms are parasitic unsegmented, bilaterally symmetrical worms that lack a coelo m but that do have three germ layers. Some forms are free living but many are parasitic. Flatworms have a nervous system that consists of head ganglion (brain), usually attached to longitudinal nerve cords that are interconnected across the body by transverse branches. Flatworms lack a respiratory or circulatory system, these functions take place by absorption through the body wall. Nonparasitic forms have a simple, incomplete gut, even this is lacking in many parasitic species. Most types of flatworms are called Parasitic tapeworms and flukes.

Examples of Animals in Phylum: Tapeworms (parasitic) Tapeworms, Class Cestode, are creatures that live as mature organisms that live on a host. These hosts include cats, dogs, cows, whales, and humans. Human hosts usually occur when uncooked, infected meat is eaten, or by ingesting the eggs. Human infection with a common dog tapeworm is transmitted by infected fleas, and is most commonly seen in children. Immature larval tapeworms may be found in various tissues throughout the body, where they may cause numerous symptoms. Clinical symptoms are usually diarrhea, nausea, and weakness.

Also, the health of the person may be compromised. Tapeworms may also disable a person's ability to absorb vitamin B 12. Flukes (parasitic) Flukes, Class Trematode, are mostly internal parasites of animals, particularly vertebrates. In fluke life cycles, eggs are shed into the intestine or bladder for quick exit into water. An egg hatches into a larva, which swims about until it finds a snail (clam in a few cases) of the correct species and then burrows into it. The larva then begins multiplying using the snail's resources.

The final stage is a sac of free-swimming larvae, called cercaria, which then burrow out of the snail and go swimming after their next host. Almost every species of vertebrate animal has flukes that are adapted for life in its organs. (blood flukes, lung flukes, bladder flukes, liver flukes, and often several kinds of intestinal flukes) Planarians Planarians, Class Turbellarian, a name that comes from the water currents stirred up by the ciliate surface of free-living flatworms. There are many kinds of turbellarian's living in virtually all watery habitats. Planarians have a three-branched digestive system with many pockets, increasing the area for digestion and absorption of food. The digestive system fills the worm's body, so there is no need for a circulatory system to transport nutrients.

During reproduction, planarians exchange sperm, and fertilization occurs internally. Planarians are the most commonly studied worm in biology. Movement Movement in some flatworms is controlled by longitudinal, circular, and oblique layers of muscle. Others move along slime trails by the beating of epidermal cilia. In some flatworms, the process of cephalization has included the development in the head region of light-sensitive organs called. Other sense organs found in at least some members of this group (not necessarily on the head) include chemoreceptors, balance receptors (statocyst's), and receptors that sense water movement (rheo receptors).

Reproduction Most flatworms can reproduce sexually or asexually. Most are. Most of these have developed ways of avoiding self-fertilization. Development may be direct (eggs hatch into tiny worms that resemble the adults) or indirect (with a ciliated larval form). Eating Flatworms get there food through other organisms. Most are predators or scavengers.

Some trap Daphnia and other small creatures by laying out trap lines made of sticky slime. Once in its trap lines, the predator feeds on the struggling prey by inserting its feeding tube called an pharynx and sucking out the prey's organs. Others feed on already dead organisms, even small planarians. Niche Flatworms are on of the laziest organism's ever. They don't have to move with their own muscles, don't have to get food for themselves and never uses much energy. Therefore I think that flatworms don't really serve any purpose in this world.