Annelida
By: Omar Abdulkader,Marcus Bray
http://www.flickr.com/photos/97968921@N00/1795523221/ (Left)
http://www.flickr.com/photos/pmforster/457146720/ (Right) Omar Abdulkader
Examples:
• Polychaets (Christmas Tree Worm) Oligochaetes (Earth Worm)
Leech
Omar Abdulkader
http://www.flickr.com/photos/tim_uk/384626933/
http://www.flickr.com/photos/theju/254592404/
http://www.flickr.com/photos/neilrsmith/537946099/
Body Symmetry
• Bilateral Symmetry
Omar Abdulkader
http://www.flickr.com/photos/35031054@N00/27111691/
Body Cavity
• Coelom is present, and is separated by septum.
Omar Abdulkader
http://universe-review.ca/I10-82-cavity4.jpg
Nervous System
• Cerebral Ganglia: A brain like pair of cerebral ganglia above and in front of pharynx near mouth.
• Nerve cords that run the length of animal.
• Ring of nerves around pharynx connects to a subpharyngealganglion, where fused pair of nerve cords run.
Omar Abdulkader
Circulatory System
• A network of vessels (closed).
• Dorsal and Ventral Vessel connected by segmental pairs of vessels.
• Dorsal Vessel + 5 pairs of vessels that circle esophagus are muscular and pump blood through circulatory system.
Omar Abdulkader
Digestive System
• One long intestine that runs length of animal (One-way).
Omar Abdulkader
http://www.zo.utexas.edu/faculty/sjasper/images/f26.5.jpg
Excretory System
• Metanephridium: excretory tubes with ciliated funnels called nephrostomes
• Remove waste from the blood and coelomic fluid through exterior pores.
• Each segment of the worm has a pair of metanephridium.
Marcus Bray
Locomotion
• All annelids have a two layer system of muscle. Longitudinal muscle surrounded by circular muscle.
• Contraction of these muscle against each other and the coelomic fluid cause the organism to move.
• Most annelids have chaetae which are bristles that provide traction for burrowing.
Marcus Bray
Skeletal Type
• No true skeleton
• Instead muscles work against the non-compressible fluid of the coelom. (hydrostatic skeleton)
Marcus Bray
Sensory Structures
• No specialized sensory structures other than nervous system
Marcus Bray
Reproduction
• Annelids are hermaphrodites meaning they have both sperm an eggs
• Sexual: Annelids reproduce sexually by aliging themselves in order to exchange sperm. Then an organ called the clitellum creates a cocoon which picks up the sperm as well as and egg and deposits the fertilized egg in the soil.
Marcus Bray
Gas Exchange
• Skin functions as respiratory organ
• Oxygen and carbon dioxide are exchanged in skin and oxygen is transferred to tiny blood vessel in epidermis.
Marcus Bray
Unique Features/Facts
• Leeches are used in medicine for blood letting
• Earthworms are beneficial to famrers because they till the earth and the soil a good texture
Quiz
1. What bristle-like structures do some annelids use to burrow?
2. What is the center of an annelid’s nervous system?
3. What functions as a hydrostatic skeleton in an annelid?
4. How does and annelid pump blood through its body?
Marcus Bray
Answers
1. Chaetae
2. Cerebral Ganglia
3. Coelom fluid
4. By utilizing the muscles in the dorsal vessel and the five pairs of vessels that circle the esophogaus.
Marcus Bray
