Phylum Annelidia
Structures: They have long bodies with segments that are divided externally by shallow ring-like constrictions called annuli and internally by septa at the same points. Their bodies are covered in cuticle that does not contain cells but is secreted by cells in the skin underneath.
Body Covering/Support: Annelids have distinct external and internal segmentation. They also have three cell layers and each has the ability to develop into various tissues or organs. They have a coelomate, which holds their organs and digestive tract, with mesoderm lining the internal cavity.
Their bodies are covered in epidermis and a thin, moist cuticle. They have no skeleton but their body shape is maintained by hydrostatic pressure.
Body Covering/Support: Annelids have distinct external and internal segmentation. They also have three cell layers and each has the ability to develop into various tissues or organs. They have a coelomate, which holds their organs and digestive tract, with mesoderm lining the internal cavity.
Their bodies are covered in epidermis and a thin, moist cuticle. They have no skeleton but their body shape is maintained by hydrostatic pressure.
Nutrition/Circulation of Nutrients: Some families of the Annelids have evolved jaws for seizing prey, biting off pieces of vegetation or grasping dead and decaying matter. Some deposit feeders live in tubes on the seafloor and use palps to find food particles in the sediment and wipe them up with their mouths. Their food then goes to the gut, which is an almost straight tube supported by the mesenteries, and goes out the anus. Their nutrients are spread through the circulatory system. They have a closed circulatory system which means that blood is stored in a group of blood vessel. Blood circulates through 2 major blood vessels that goes from head to toe. The dorsal vessel goes to the head and the ventral muscle goes from head to toe. In each segment there are tiny vessels that connect the two together and they then supply blood to the organs.
Respiration: Annelids that live in the water breath through gills and the ones that live on land, breathe in oxygen and give off carbon dioxide through their moist skin.
Nervous system: they have a well developed nervous system. It consists of a brain and a few nerve cords. Marine annelids have sensory tentacles, chemical receptors, statocysts that helps detect gravity and 2 pairs of eyes to detect stimuli.
Respiration: Annelids that live in the water breath through gills and the ones that live on land, breathe in oxygen and give off carbon dioxide through their moist skin.
Nervous system: they have a well developed nervous system. It consists of a brain and a few nerve cords. Marine annelids have sensory tentacles, chemical receptors, statocysts that helps detect gravity and 2 pairs of eyes to detect stimuli.
Reproduction: They can reproduce asexually, by dividing into two or more pieces or by budding off a ne individual while the parent remains a complete organism. They also reproduce sexually by attaching and exchange sperm. Then the sperm is stored in special sacs. When the eggs are ready fertilize specialized segments would release a mucus ring where the egg and the sperm is released. This is where the fertilization occurs. Afterwards the ring slips off the worm's body and forms a sack. Weeks after this baby worms hatch.
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