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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