Module 9

Question 1

Define the term: Intertidal zone

Answer 1

The area off shoreline between the highest high and lowest low tides

This zone is characterized by its unique environmental conditions and biodiversity.

Question 2

Define the term: Substrate

Answer 2

The bottom surface of a marine habitat

Substrate can vary in composition, including sand, mud, or rocky surfaces.

Question 3

Define the term: Epifauna

Answer 3

Benthic animals that move about the surface of the sea bottom

Examples include crabs and starfish.

Question 4

Define the term: Sessile

Answer 4

Organisms that are firmly attached to a substrate

Sessile organisms do not move and include barnacles and corals.

Question 5

Define the term: Desiccated

Answer 5

When an organism has lost its body moisture

This condition can affect the survival of intertidal organisms during exposure to air.

Question 6

Define the term: Vertical zonation

Answer 6

Noticeable horizontal bands of organisms living within a certain range in the intertidal zone

This zonation is influenced by factors such as tidal patterns and environmental conditions.

Question 7

Define the term: Ecological succession

Answer 7

A gradually increasing occupation of new organisms into a specific area

This process can lead to changes in community composition over time.

Question 8

Define the term: Infauna

Answer 8

Organisms that live under the sediment of an ecosystem

Infauna play important roles in nutrient cycling and sediment structure.

Question 9

What is the main reason there is such a diversity of life in the intertidal zone?

Answer 9

The environmental conditions vary dramatically in the intertidal zone.

Question 10

What are the varying abiotic conditions under which an intertidal organism must live?

Answer 10

Intertidal organisms are exposed to dry and wet conditions, pounding wave action, and varying temperatures and salinities.

Question 11

What benefit does a sessile organism have over a mobile organism in the intertidal area?

Answer 11

Sessile organisms are firmly attached to a substrate, so they are less likely to be tossed around due to the movement of waves.

Question 12

What is a drawback of being sessile?

Answer 12

Sessile organisms cannot move to a better location if conditions get bad.

Question 13

What are the 2 major ways that organisms can prevent desiccation in upper intertidal areas?

Answer 13

• Some organisms can move to moister, protected areas under rocks or in tide pools
• Others can retain moisture in their bodies.

Question 14

A marine biologist measures the salinity of a tide pool at low tide. What may have happened to cause the lower salinity level?

Answer 14

There may have been rain or possibly freshwater from shores draining into the tide pool, resulting in dilution of the water inside the tide pool.

Question 15

How do sessile intertidal organisms deal with increases in sunlight exposure?

Answer 15

Some store extra water and allow it to evaporate, others have lighter colored shells.

These adaptations help to manage temperature increases due to sunlight.

Question 16

Why do organisms living in the lower areas of the intertidal zone have less of a problem feeding?

Answer 16

Organisms in the lower areas are underwater longer than organisms in the upper areas.

This increased time submerged allows for more feeding opportunities.

Question 17

Why do most sessile organisms in the intertidal produce planktonic gametes?

Answer 17

The gametes must move in order to find another gamete to fertilize.

Sessile organisms cannot move to locate mates.

Question 18

Explain why waves usually reach a shore nearly parallel to it.

Answer 18

As a wave reaches shore, the side closest to shore encounters shallow water first, slowing down while the other end continues faster, causing refraction.

This process results in waves approaching the shore at a nearly parallel angle.

Question 19

What are two possible features that might cause weak wave action in a rocky shoreline?

Answer 19

Sand bar or canyon.

These features can disrupt wave energy, leading to reduced wave action in specific areas.

Question 20

What do mussels produce that allow them to attach to a substrate so strongly?

Answer 20

byssal threads

Byssal threads are strong, fibrous structures produced by mussels to anchor themselves to surfaces.

Question 21

Why do the fishes in the intertidal zone rarely have swim bladders?

Answer 21

They have to live on the bottom so they can cling to the substrate

Question 22

What events can cause new space to become available in an intertidal area?

Answer 22

• Predators can remove organisms, resulting in new space
• Heavy surf can wash away organisms or turn over the rocks on which they are living
• Floating debris can crush organisms

Question 23

What types of abiotic factors determine the upper limit of living space for an intertidal organism?

Answer 23

Abiotic factors: salinity, temperature, moisture availability

Question 24

What types of biotic factors determine the lower limit of living space for an intertidal organism?

Answer 24

Biotic factors: predation and competition for space

Question 25

Why is the upper intertidal zone sometimes called the 'splash zone'?

Answer 25

Because the main way it gets water is from splashing waves

Question 26

Why is the upper intertidal zone sometimes called the Littorina zone?

Answer 26

Because members of the genus Littorina are the most common organisms in the upper intertidal zone

Question 27

What abiotic factor mostly determines how high barnacles can live in the middle intertidal zone?

Answer 27

Dryness ## Footnote Dryness affects the ability of barnacles to survive in higher zones due to exposure to air.

Question 28

What two biotic factors mostly determine how low barnacles can live?

Answer 28

* Predation * Competition ## Footnote These factors influence the survival and growth of barnacle populations in lower intertidal zones.

Question 29

In a rocky intertidal beach, if an area has mostly chitons feeding on macroalgae, would this area be considered a climax community?

Answer 29

No ## Footnote A climax community typically has dominant organisms such as mussels in the middle intertidal zone.

Question 30

In the middle intertidal zone, which boulder was more recently cleared of its living organisms: the one covered with mussels or the one covered with successional algae?

Answer 30

The rock with the algae ## Footnote The presence of algae suggests that the rock was cleared more recently compared to the rock covered with mussels.

Question 31

Which zone of the rocky intertidal has the greatest diversity of organisms?

Answer 31

The low intertidal ## Footnote The low intertidal zone is underwater the longest, allowing for greater survival of various organisms.

Question 32

Fill in the blank: The middle intertidal zone has many vertical zones because the levels can _____dramatically.

Answer 32

vary ## Footnote This variation in levels leads to different habitats and conditions for organisms.

Question 33

What is the dominant species of of the upper intertidal zone?

Answer 33

Littorina

Question 34

What is the limiting recourse for the upper intertidal zone?

Answer 34

Water

Question 35

What is the dominant species in the middle intertidal zone?

Answer 35

Mussels

Question 36

What is the limiting recourse of the middle intertidal zone?

Answer 36

Space

Question 37

What is the dominant species in the lower intertidal zone

Answer 37

Seaweeds

Question 38

What are the limiting resources of the lower intertidal zones?

Answer 38

Space and light

Question 39

Which two sediment materials make up mud?

Answer 39

Clay and silt

Question 40

Place these sediment types in order from smallest to largest: sand, silt, clay.

Answer 40

Clay, silt, sand

Question 41

List these intertidal sediments in order of increasing wave action: sandy, rocky, muddy.

Answer 41

Muddy, sandy, rocky

Question 42

Why must most organisms living in a muddy intertidal area live buried near the surface of the mud?

Answer 42

They cannot live on top of the mud because the wave action pushes them away, as there is nothing on which to get a firm grip. They have to live near the surface of the mud because there is little water movement through the substrate and therefore little oxygen available

Question 43

What kind of organisms will you find deep in the substrate of a muddy intertidal zone?

Answer 43

Anaerobic bacteria ## Footnote Anaerobic bacteria do not require oxygen to survive

Question 44

Why do so many organisms in the muddy intertidal zone eat detritus?

Answer 44

There are not many primary producers in the muddy intertidal. Thus, the organisms must eat detritus instead of primary producers.

Question 45

Which area will have greater zonantion: sandy or muddy intertidal? Why?

Answer 45

The sandy intertidal will have greater zonation because it is more varied in its habits. ## Footnote In muddy areas, the bottom retains water despite the abscence of the tide, so the type of habitat does not change much at the high and low tide marks.