The Diversity of Ocean Life 15.2

Plankton• Passively drifting or weak swimming

organisms that cannot move independently of ocean currents.

Phytoplankton• Algal plankton, the most important

community of primary producers in the ocean.

Zooplankton • Animal plankton.

Nekton• Organisms that can move independently of

ocean currents by swimming or other means of propulsion.

Benthos • The forms of marine life that live on or in the

ocean bottoms.

Photic Zone• The upper part of the ocean into which

sunlight penetrates.

Intertidal Zone • The area where land and sea meet and

overlap; the zone between high and low tides.

Neritic Zone

• The marine-life zone that extends from the low-tide line out to the shelf break.

Oceanic Zone

• The marine-life zone beyond the continental shelf.

Pelagic Zone

• Open ocean of any depth; animals in this zone swim or float freely.

Benthic Zone • Othe marine-life zone that includes any sea-

bottom surface regardless of its distance from shore.

Abyssal Zone • A subdivision of the benthic zone

characterized by extremely high pressures, low temperatures, low oxygen, few nutrients, and no sunlight.

Key Concept

• How can marine organisms be classified?–Marine organisms can be classified

according to where they live and how they move.

Key Concept

• What is the difference between plankton and nekton?–Plankton drift with ocean currents and

Nekton swim independently of the ocean currents.

Key Concept

• In which area of the ocean can most benthos organisms be found living?–Most benthos organisms are living on

or in the ocean bottom.

Key Concept

• What factors are used to divide the ocean into marine life zones?–Three factors are used to divide the

ocean into distinct marine life zones: the availability of sunlight, the distance from shore, and water depth.