4. which of the following properties most determines water’s vertical position in the ocean?
organic content
density
velocity
oxygen content
5. which of the following is not a category of marine organisms?
plankton
nekton
aphotic
benthos
6. which of the following is a type of plankton?
shark
algae
squid
crab
7. which of the following is a type of nekton?
shark
zooplankton
bacteria
sea star
8. how do animals survive in the deeper parts of the seafloor?
they feed on each other.
they feed at the surface.
they photosynthesize.
none of the above

4: density.  

5: aphotic  

6: algae  

7: shark  

8:  They feed at the surface

4. density: The vertical position in the ocean represents the density of the water, the density of the water depends upon the temperature of the water. The colder the water the more will be it's density and hot water exhibit low density. Hence, water depending upon the density forms a gradient in water body like ocean.

5. aphotic: Aphotic does not represent a category or animals instead it represents the zone of the lake or ocean which receives very little or no sunlight.

6. algae: Unicellular green algae can be described as plankton. Planktons are unicellular, autotrophic organisms.

7. Shark: A nekton can be defined as an aggregate of actively swimming aquatic animals. This includes large diversity of molluscs, vertebrates and crustaceans. Shark is a vertebrate nekton.

8. They feed at the surface: The animals living near or on the sea floor obtain food by feeding on the surface of the sea floor as the sea floor are the rich source of organic matter accumulates after the partial or complete decomposition of oceanic biological waste such as dead parts of plants and animals.

a. to encourage apoptosis