This activity explores an image of early embryonic cells, which serves as a phenomenon for learning about cell division and development.

The sand dollar embryo in this image is in an early stage of development called a blastula. Certain groups of cells in the blastula are synchronized to divide at the same time through mitosis. Some of these cells will eventually give rise to the sand dollar’s germ cells. Others will play important roles in various developmental processes, such as cell differentiation, the formation of the digestive system, and the development of the exoskeleton. Despite their different characteristics and roles, all of the sand dollar’s cells (except for eggs or sperm) are genetically identical due to mitosis.

The “Educator Materials” document includes background information and implementation suggestions for using the image as a phenomenon. The “Student Handout” includes the image and background information.

Image by George von Dassow, Oregon Institute for Marine Biology