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Phylum Porifera are simple organisms which include sponges. They have spicules which are made of silica or calcium which form their "skeleton". There are two layers of cells that make up their body with mesoglea, a jelly-like substance in between. They have a body cavity where there are no organ systems present. A constant flow of water into the sponge brings tiny organisms into the body cavity where digestion occurs. The water flow brings in oxygen and helps to remove wastes. They are sessile and reproduce both asexually by budding and sexually by releasing sperm and eggs into the water.
Phylum Chordata are complex organisms with a notochord. They include animals with backbones such as Mammals, Amphibians, Reptiles, Birds and Fish. They have a hollow dorsal nerve cord. Chordates have skeletons, organ-systems that carry out life functions and are capable of sexual reproduction. Chordates have a one-way digestive system and a tube within a tube body plan.
Phylum Annelida includes earthworms, marine worms and leeches. They possess a segmented body plan with a tube within a tube arrangement, where the body tube encases the one-way digestive tube. They are hermaphrodites with both sexes in one body. They have moist bodies through which respiration occurs. They have closed circulation with multiple hearts.
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