Final answer:
The zero point refers to sea level, from which depths in the ocean are measured. Marine life like sea stars and sharks is adapted to specific ocean zones characterized by differing conditions such as light availability and water pressure. These zones include the intertidal, neritic, and abyssal zones.
Step-by-step explanation:
The zero in the situation described refers to the sea level. In marine biology, sea level is the base measure from which ocean depths are measured. Therefore, when we say a sea star is found at an ocean depth of two feet, it means it is two feet below sea level; similarly, when a shark is seen at an ocean depth of five feet, it is five feet below sea level.
Life in the ocean exists at various depths, categorized into distinct zones such as the intertidal zone, the neritic zone, and the abyssal zone. The intertidal zone is where organisms face air exposure and sunlight during low tide, the neritic zone extends to the edge of the continental shelf at depths where sunlight supports photosynthesis, and the abyssal zone starts from the ocean depths of 4000 m or greater.
Marine animals are adapted to live in these different zones. For example, certain sea stars and mussels can be found in the intertidal zone where they must withstand the drying effects of air exposure and the physical pounding of waves. On the other hand, sharks commonly reside in the neritic zone, but as cartilaginous fish, they can also be found across various other depths of the ocean.