Complex sentence: Multiple mating ensures fertilization of all the female's eggs and often results in multiple paternity of a clutch, which is a common phenomenon exhibited by many marine and freshwater turtles.
Split into simpler sentences: Multiple mating ensures fertilization of all the female's eggs and often results in multiple paternity of a clutch. Multiple paternity is defined as offspring having genetic traits from more than one male father, and this phenomenon is exhibited by many marine and freshwater turtles.