What is a Flatworm?
Definition: a phylum of worms having bilateral symmetry and a
soft, usually flattened body, comprising the flatworms
Definition: a phylum of worms having bilateral symmetry and a
soft, usually flattened body, comprising the flatworms
Body Plan:
Because flatworms are thin and most of their cells are close to the external environment, materials can pass easily into and out of their bodies. All flatworms rely on diffusion for some essential body functions, such as respiration, excretion, and circulation. Feeding: Free-living flatworms can be carnivores that feed on tiny aquatic animals, or they can be scavengers that feed on recently dead animals. They are like cnidarians with their digestive cavity. Parasitic worms feed on blood, tissue fluids, or pieces of cells within the host's body. Respiration, Excretion & Circulation: Because their bodies are so flat and thin, many flatworms do not need a circulatory system to transport materials. Instead, flatworms rely on diffusion to transport oxygen and nutrients to their internal tissues, and to remove carbon dioxide and other wastes from their bodies. |
Response:
Most flatworms have more complex structures for detecting and responding to external stimuli than those of cnidarians or sponges. They have ganglia, which controls their nervous system. Parasitic flatworms interact little with their external environment and typically have a less complex nervous system. They have eyespots that can detect changes in the amount of light in their environment. In addition to that, most have specialized cells that detect external stimuli, such as chemicals found in food or the direction in which water is flowing. Movement: Free-living flatworms typically move in two ways, such as cilia and muscles cells. Reproduction: Most of them are hermaphrodites that reproduce sexually, but asexual reproduction is common also. Parasitic flatworms often have complex life cycles that involve both sexual and asexual reproduction. |