We are working on “note taking” skills. The boys want to research until the cows come home. This series of exercises is designed to provide them with a limited amount of information that they synthesis into paragraphs or in BR’s case isolated notes.
Also we are to begin with creatures with notochords this week. I realized the implications of the notochord and decided to move backward a bit to discuss differences among species beginning with creatures with a coelom and those without. This discussion has its roots in the embryonic development of creatures and goes to things like why there are no “identical twin” worms.
Coelom advantages and divisions among creatures with a coelom. By AV
A coelom is a cavity in the body that surrounds or almost surrounds the gut. If an animal has no coelom and during digestion if the animal has to make a sharp turn, the turn will cut off the digestive track. Think of it like a kink in a hose interfering so no food passes through. There are other reasons that a coelom is optimal. It protects organs, allows for more complex organs, allows for egg storage before release, allows for a true hydrostatic system, and the fluid in the coelom can help with respiration.
The formation of the coelom is simple. There are two ways to do it: protostomes’ coelom come from the ectoderm splitting away in the early stages of the embryo and deuterstomes’ coelom comes from an expansion of the gut in a pinch and pull action.
An early embryo begins as a ball of cells. This ball will develop a hole. When the hole forms in the protostomes, it become the opening for the mouth, but when it forms in deuterstomes, it becomes an anus.
JV went with his small is better theory of life. I photographed it.
BR did an amazing job of copying my notes and synthesizing the overheads we used into a good explanation. (The College of Charleston gave us their overheads as they were updating their curriculum. Thank you Dr. Wiseman)