The Tidal Ecosystem

1
The Tidal Ecosystem

1. What causes the oceans to bulge out in the
   direction of the moon?
2. What would happen to the water on the earth if
   the moon disappeared?

• WHAT CAUSES THE TIDES?
• Tides are caused by the gravitational interaction
  between the Earth and the Moon.
• The gravitational attraction of the moon causes
  the oceans to bulge out in the direction of the
  moon.
• Another bulge occurs on the opposite side, since
  the Earth is also being pulled toward the moon
  (and away from the water on the far side).
• Since the earth is rotating while this is
  happening, two tides occur each day. Isaac Newton
  was the first person to explain tides
  scientifically.

2
Tides

• The sun and the moon move in cycles affecting the
  flow and ebb of the tides.
• Here in the Pacific, we have two high and low
  tides of unequal heights each day.
• Between each high and low tide there is a time
  difference of approximately six hours.

1. How many high tides are there in a day?
2. What is happening to the water between high tide
   and low tide?

3
Tide Zones

• Tidepools, which are exposed at low tide, occur
  within a small strip of land known as the
  intertidal zone.
• Sandwiched between the shore and the ocean,
  tidepools are extraordinary, teeming with
  hundreds of marine organisms.
• In the picture Notice that some of the sand is
  completely under the waves, some is wet, some is
  drying out, and some is dry.

5. How do you think the tide zones at a beach
can be found? (think about the picture)
4

1. Which zone is underwater most of the time?
2. Which one is the driest tide zone?
3. Are there actual lines that separate the zones on
   the beach?
4. Are the animals the same in all tide zones?
   (Look at the picture.)
5. Give two ways that you could tell the tide zones
   apart if you were at the beach.

5

• 11.
• Draw this zone diagram (you can leave out the
  organisms. Just draw the rock.) Leave space to
  write things.
• Label each zone
• Go back through slides 13-44 of yesterdays
  assignment. Write the name of the organism in
  the appropriate zone or zones.