February 4, 2011
For the past few weeks we have been learning about Invertebrates. Invertebrates are animals that do not have a backbone and have a more simple body structure than animals that belong to the Chordata Phylum (mammals, birds, reptiles, amphibians, fishes) Of the million or more animal species in the world, more than 98% are invertebrates. We have enjoyed investigating one invertebrate in particular, the planaria, which is a flatworm that can regenerate.
Planaria belong to the phylum, Platyhelminthes. They have a triangular head and two eye spots (which really only detect light, not images.) Planarians suck up their meals such as clam shrimp, water fleas and decaying animals with a straw-like mouth. Don’t look for the mouth on its head. The mouth comes right out of the planaria’s belly! It doesn’t need gills or lungs. It gets oxygen right through its skin! It is interesting that if you cut a planaria in two from head to tail, it will regenerate. Both halves will live and grow new, complete bodies. What did you learn from our planaria lab?