Phylum Annelida
The name Annelida is derives from the Latin word annellus, meaning "Little ring." Referring to the ring like appearance of the annelids body sections. Annelids are worms with segmented bodies. They have a true coelom that is lined with tissue from mesoderm.
Body Plan:
Annelids have a very complex organ systems. Many of these systems are different because of the segmented body plan of this group. (Shown right) Feeding:
Annelids can be filter feeders or predators. Many use their pharynx to get good. Some have two sharp jaws to attack prey. Some pharynx are covered in mucus to feed on decaying vegetation. Other annelids filter feed, they fan water through tube like burrows and catch food particles in a mucous bag. Respiration:
Aquatic annelids breathe through gills. Land-dwelling annelids take in oxygen and give off carbon dioxide through their moist skin from the coating of mucus. Reproduction:
Most annelids reproduce sexually. Some species use external fertilization and have separate sexes. Other annelids are hermaphrodites, individuals rarely fertilize their own eggs. Two worms attach to each other and exchange sperm, and store it until eggs are ready for fertilization. |
Circulation:
Annelids have a closed circulatory system, which means blood is contained within a network of blood vessels. The blood circulates through two major blood vessels that run from head to tail. Excretion:
Digestive waste passes out through the anus. While cellular waste containing nitrogen is eliminated by nephridia, excretory organs that filter fluid in to the coelom. Response:
Annelids have a well-developed nervous system consisting of a brain and several nerve cords. Free-living marine annelids have sensory tentacles, chemical receptors, statocysts that detect gravity and eyes. Earth worm digging in the ground: http://www.youtube.com/watch?v=W1HfV9vHEmA
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