- Usual salinity for the oceans is about 3.5% or 35 parts per thousand.
- Some regions in areas of high evaporation, like the Dead Sea, have exceptionally high
salinities. - The photic zone is the surface layer of the oceans, down to about 200m, where there
is enough available light for photosynthesis. - Below the photic zone, the vast majority of the oceans lies within the aphotic zone,
where there is not enough light for photosynthesis. - On average, the ocean floor is about 3,790m but there are ocean trenches as deep as
10,910m. - The ocean has many biological zones determined by availability of different abiotic
factors. - Neritic zones are nearshore areas, including the intertidal zone. Oceanic zones are
offshore regions of the ocean.
Review Questions
- What was the name of the single continent that separated to form today’s continents?
- From what three sources did water originate on Earth?
- What percent of the Earth’s surface is covered by water?
- How do the oceans help to moderate Earth’s temperatures?
- Over time, the Earth’s oceans have become more and more salty. Why?
- What is the most common substance that is dissolved in ocean water?
- What is density?
- Compare and contrast the photic and aphotic zones.
- Describe the types of organisms found in the intertidal, neritic, and oceanic zones.
Give examples of a life form you think might be found in each.
Vocabulary
aphotic zone
The zone in the water column deeper than 200 m. Sunlight does not reach this region of the
ocean.
biomass The total mass of living organisms in a certain region.
current The movement of water in a stream, lake, or ocean.
density Mass per volume. The units for density are usually g/cm^3 or g/mL.
intertidal zone The part of the ocean closest to the shore, between low and high tide.