Complex sentence: The Marine Mammal Center is a private, non-profit U.S. organization that was established in 1975 for the purpose of rescuing, rehabilitating, and releasing, marine mammals that are injured, ill, or abandoned.
Split into simpler sentences: The Marine Mammal Center is a private, non-profit U.S. organization that was established in 1975 for the purpose of rescuing, rehabilitating, and releasing, injured, ill, and abandoned marine mammals. The Center's primary mission is to rescue animals that are injured, ill, or abandoned.