1. Making Model Embryos: by: Jewel Reuter, LA Virtual School Donald Cronkite, Hope College [Attachment #5]

2. The Medaka (A Fish) Start with an orange and a lump of modeling clay This will be the yolk of the egg This will be the part with the nucleus

3. A Question One part of the egg will divide to form many cells. The other part will not divide, but provides nourishment for the embryo. Which part of our model do you think is which? Which part will be the model’s yolk? [ ? [ Which part will be the part of the model that divides? [ ? [

4. The Answer One part of the egg will divide to form many cells. The other part will not divide, but provides nourishment for the embryo. Did you come up with the answer? Which part will be the model’s yolk? [ ? ] Which part will be the part of the model that divides? [ ? ]

5. The One-Cell Stage

6. To Make More Stages Break your clay into equal sized bits, thus making two cells, break each of those in half to form four cells and so on until you reach 32 cells. Lay them down on the orange each time as shown on the diagrams. Study the pictures of development before you begin so that you can make accurate models of the stages.

7. Making the Fish’s Yolk Sac After many divisions, the cells have divided to produce very small cells. The whole layer of cells moves down to form a yolk sac around the yolk. Then the embryo can get nutrients from the yolk. Consult the pictures of fish embryos to see how your model should look.

8. Making the Fish’s Yolk Sac Make a pancake of your clay, and put it on the orange to look like the stage when the cells move down over the yolk. Then make a ridge along the center of your developing yolk sac to represent the early formation of the embryo.

9. Making the Fish’s Yolk Sac the ridge that will become the fish the growing yolk sac the yolk

10. A Model of a Human Embryo Human embryos have only a tiny amount of yolk. The whole egg cell, which is very small, divides again and again to form a little ball of cells. Study the pictures of early human embryos, and make each cell division for the first 5 divisions. How many cells are produced in 5 divisions?

11. The Fertilized Egg’s Journey The egg is fertilized at the very top of the oviduct. Then it divides as it moves down the tube, taking about 7 days for the journey. 1 Week

12. The Blastocyst When the dividing egg reaches the bottom of the oviduct, it enters the uterus where it will live for another 35 weeks attached to the mother. When the embryo reaches the uterus, it is a “blastocyst,” a hollow ball with a lump of cells at one end. Study the pictures of blastocysts, and then figure out how to make one with clay.

13. Attached Make a flat piece of clay to represent the wall of the uterus, and then attach the embryo by the thin membrane.