OBJECTIVE: The student shall demonstrate their ability to work in a lab environment with a new organism by carefully and efficiently carrying out fertilization of the sea urchin, writing up a lab report, and answering the implication questions.
PURPOSE: This is the start of "life", where we all began. A lot can go wrong, too many sperm and the eggs die, too few and fertilization doesn't occur. Temperature, salinity, and other environmental factors have to be just right and make careful attention to laboratory protocols essential. This lab helps students see the complex requirements for successful fertilization and healthy development of embryos.
SET: As we saw yesterday, most of the organisms with which we are familiar, including humans, started with sperm and eggs. How does a new individual develop from sperm and egg to an adult organism? Today we witness, first hand, the next step in this process, fertilization. The new beginning of an unique organism.
STRUCTURED PRACTICE: Ask and answer questions while introducing the model to insure active participation and check understanding.
GUIDED PRACTICE: Students perform fertilization under their microscopes and make observations. Students are also given pre fertilized embryos that are reaching the first cell division stage for observation.
Why does it take 200 million sperm to fertilize a human egg?
NONE OF THEM ARE WILLING TO STOP AND ASK DIRECTIONS.
Tomorrow we will continue with sea urchin development by observing embryos at latter stages of development.
NOTES: Remember to fertilize eggs one hour before in order to have embryos at the first division stage.