Complex sentence: When this occurs, the animal typically starves, because the plastic blocks the animal's digestive tract.which block the passage of air and kill them Marine mammals sometimes become entangled in plastic products such as nets, which can harm or kill them.
Split into simpler sentences: When this occurs, the animal typically starves, because the plastic blocks the animal's digestive tract. Which blocks the passage of air and kill them Marine mammals sometimes become entangled in plastic products such as nets, which can harm or kill them.