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Life In The Ocean

Ninety seven percent of the water on or near Earth's surface is ocean water. Living organisms in the ocean have adapted to the ocean environment. Ocean environments are controlled by many components. A few of the important components include temperature, light, depth, nutrients, currents, tides, waves and the nature of the sea floor.

Question—How do the following affect the temperature of ocean water?

  • Depth
  • Latitude
  • Currents

Question—How do the following affect the salinity of ocean water?

  • Temperature
  • Latitude
  • Rivers
  • Evaporation

Question—How is density of ocean water affected by both salinity and temperature?

Consider the underwater organism known as kelp. It must be attached to the bottom and yet be in water that is shallow enough for light to penetrate. This quick growing organism also requires an ample supply of nutrients, which on the west coast are provided by upwelling currents caused by prevailing west winds.
Now consider tropical corals. These must be attached to the bottom in areas where waves and currents bring food. Each type of coral requires specific temperatures.  Clear water results from low-nutrient water.
Lastly, consider the large mammals known as blue whales. These huge organisms exist in all open oceans rich in krill. The Antarctic krill feeds mainly on photoplankton near the ocean's surface. Other krill feeds on both zooplankon and photoplankton near the ocean's surface.

Exploring the Ocean

Visualize the parts and characteristics of the ocean and the ocean floor along with the characteristics of the organisms inhabiting the different parts of the ocean.


  • One 14” X 18” paper
  • Crayons or colored pencils
  • Library or internet access


  1. Sketch an area for the continental margin and deep ocean basin on the paper. This is just a simple profile or cross section of the ocean.
  2. Draw and label the basic parts of the continental margin. Include a shelf, slope, and rise. Make sure you leave a little coastline!
  3. Draw and label the basic parts of the deep-ocean basin. Include a large abyssal plain, mid-ocean ridge, rift valley, seamount, and ocean trench.
  4. Label the benthic environment and pelagic environment.
  5. Label the following zones in the benthic environment: intertidal, sublittoral, bathyal, abyssal, and hadal. Color each zone a different color. Label the water’s depth at each zone boundary.
  6. Label the neritic and oceanic zones in the pelagic environment. Color each zone a different color. Label the water’s depth at each zone boundary.
  7. Label where the three main groups of marine life (plankton, nekton, and benthos) are found in the ocean.
  8. Draw and label at least one marine organism that inhabits each zone.


  1. What features on your map occur at tectonic boundaries?
  2. At which locations would you expect to find the coldest water and the least sunlight? Why?
  3. How does this affect what type of organisms can life in these locations?
  4. Which would be the best zone for fishing? Why?
  5. List three features of animals that help them live in the intertidal zone.
  6. How would the ocean’s ecological zones change if the ocean level dropped 300 meters?
  7. Why do scientists know so little about the abyssal and hadal zones?
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Updated October 24, 2008 by: Glen Westbroek

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