In sea urchins ,the "fast block" and the longer-lasting "slow block" to polyspermy ,respectively ,are membrane depolarization and the cortical reaction .
Sea urchins belongs to the animalia kingdom , Echinodermata Phylum, and Echinoidea class . they are small marine animals .
Sea urchins are spiny , globular . they have their habitat in coral reefs and rocky ocean floor . they are omnivores .they depend on algae for food . average life span of sea urchin is 15-200 years .
Polyspermy is the fertilization of egg by more than one sperm . diploid organisms normally contain two copies of each chromosome ,one from each parents .
This may occurs because sperms are too efficient at reaching and fertilizing ovum which leads to competition between sperms .
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