The cortical reaction of sea urchin eggs functions directly in a. the formation of a fertilization envelope. b. the production of a fast block to polyspermy. c. the generation of an electrical impulse by the egg. d. the fusion of egg and sperm nuclei.

Key Concepts

Cortical Reaction

The cortical reaction is a crucial process that occurs in the egg of sea urchins following fertilization. It involves the release of enzymes from cortical granules, which leads to the modification of the egg's outer layer, forming a fertilization envelope. This envelope serves as a barrier to prevent additional sperm from entering the egg, thus ensuring that only one sperm fertilizes the egg.

Fertilization Envelope

The fertilization envelope is a protective layer that forms around the egg after fertilization, primarily as a result of the cortical reaction. This structure is essential for preventing polyspermy, which is the fertilization of an egg by multiple sperm. The formation of this envelope is a key mechanism that ensures the genetic integrity of the resulting zygote.

Polyspermy Prevention

Polyspermy prevention is a critical biological mechanism that ensures that only one sperm fertilizes an egg. In sea urchins, this is achieved through both a fast block, which involves a rapid change in the egg's membrane potential, and a slow block, which is the formation of the fertilization envelope. These processes work together to maintain the proper diploid state of the zygote and prevent developmental issues.