M17 - 3

Question 1

Label the figure that shows the effect of the moon’s gravity on the Earth’s tides.

Answer 1

A = tidal bulge

B = North Pole

C = tidal bulge

D = Earth

E = Moon

F = Earth’s rotation on axis (once every 24 hours)

G = moon orbits the earth (about once a month)

Question 2

• Draw a diagram showing the earth, moon and sun when it is a spring tide.
• Indicate the tidal bulge and the gravitational pull of the moon and the sun.

Answer 2

Question 3

Why does the tidal bulge form on both sides of the earth, rather than just on the side that the moon is pulling from?

Answer 3

• As the moon pulls on the earth and its waters, the earth pulls back.
• As the earth pulls back, it pushes its waters that are on the opposite side of the moon so that the tidal bulges on both sides of the earth are equal.

Question 4

Most coastal areas will experience 2 high tides and 2 low tides every day.

How does this occur?

Answer 4

• The moon pulls the waters of the earth by its gravitational pull, causing a tidal bulge on the earth.
• The earth rotates on its axis once every 24 hours.
• This means that a coastal town or city will “pass through” the 2 tidal bulges on the earth in one day.

Question 5

What is spring tide and why does it occur?

Answer 5

• A spring tide means that the high tide is very high and the low tide is very low.
• The reason for a spring tide is that the moon’s orbit lines up with the sun.
• This happens at full moon and new moon.
• The sun’s gravitational pull adds to the moon’s gravitational pull, which means that the tidal bulges on the earth get bigger.

Question 6

How does the moon’s gravity affect life in an ecosystem in the high tide zone.

Answer 6

• The plants and animals in the high tide zone rely on the tide to bring oxygen, food and other nutrients into their tide pools at every high tide.

Question 7

Give 2 examples of adaptations that animals in the low tide zone have developed to suit their environment.

Answer 7

1. The plants and animals in the low tide zone have developed adaptations like suckers to cling to the rocks so that they are not washed out to sea.
2. Many animals also have shells to prevent drying out when they are exposed to sunlight.

Question 8

How are plants in the high tide zone adapted to their environment?

Answer 8

• The plants and animals in the high tide zone need to be adapted to live in water and withstand the beating waves and rough sea when the tide comes in.
• They also have to withstand high temperatures so that they can survive on the rocks in the sun when the tide goes out.

Question 9

Explain how the high and low tides affect the ecosystem of the low tide zone.

Answer 9

• The low tide zone is usually underwater, but will be exposed at low tide.
• The water provides the plants and animals in this zone with some protection against predators, because of the wave action of the tides.
• The water also protects this ecosystem from excessive heat from the sun.