Biology Forums - Study Force

During fertilization in sea urchins, Steinhardt and his colleagues observed that the sperm-induced rise in cytoplasmic Ca2+concentration correlates with the formation of the fertilization envelope, which blocks fusion of other sperm with the egg. Look at the image below to review the terms. Note that the vitelline layer is sometimes called the vitelline envelope.

An increase in the concentration of Ca2+ in the egg's cytoplasm triggers what is called the cortical reaction. In this activity, you will place the events of the cortical reaction in the correct sequence.


Drag the labels to the appropriate targets to indicate the sequence of events occurring between fusion of the sperm and egg and formation of the fertilization envelope.

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