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Intertidal zone

The area of shoreline between high and low tides


The bottom surface of a marine habitat


Benthic animals that move about the surface of the sea bottom are firmly attached to it


A member of the epifauna that lives attached to a substrate


A term referring to an organism that has lost its body moisture

Vertical Zonation

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

Ecological Succession

A gradually increasing occupation of new organisms into a specific area


Organisms that live under the sediment of an ecosystem

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

It has the greatest variation of environmental factors

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

Intertidal organisms must protect themselves from desiccation, temperature, and salinity fluctuations

What benefit does a sessile organism have over a mobile organism in the intertidal area? What is a drawback of being sessile?

Sessile organisms can attach themselves to protected areas during low tide and are more likely to survive. If the organisms are attached to an exposed area however, they do not survive.

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

1) Move to protected areas
2) Seal in moisture

A marine biologist measures thesalinity of a tide pool at low tide. He finds the salinity to be much lower than that of the ocean. What may have happened to cause the lower level?

Salinity levels in tide pools decrease with rain because of the fresh water.

How do sessile intertidal organisms deal with increases in sunlight exposure, which can cause large increases in temperature?

Attach themselves from the larval stage to a protected area

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

The lower intertidal zone is usually- but not always- entirely submerged underwater. This allows for slow moving animals to feed all the time. Organisms in the upper zone have a bigger chance of becoming the meal.

Most sessile organisms in the intertidal produce planktonic gametes. Why?

They become attached from the larval stage to a certain surface/substrate

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

As the waves go closer to shore the majority of the wave is moving slowly, but the edge farthest from the shore is moving more quickly to 'catch up.' But it isn't perfectly parallel

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

Byssal threads.

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

Instead of a swim bladder, most fish in the intertidal zone have suction cup-shaped pelvic fins.

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

Some of the biotic factors clear spaces by removing organisms such as mussels. Abiotic factors i.e. heavy surf, driftwood, and tumbling rocks push organisms off of the substrate and create new living spaces.

What types of factors (abiotic or biotic) determine the upper limit of living space for an intertidal organism? What about the lower limit?

The upper limit is determined by abiotic factors. The lower limit is usually determined by biotic factors.

Why is the upper intertidal zone sometimes called the "splash zone?" Why is it sometimes called the Littorina zone?

The "splash zone" is rarely fully submerged in water. Organisms in this zone are very tolerant of temperature changes.

There are many vertical zones within the middle intertidal zone. Why?

The seasonal variation of seasonal tides results in many smaller divisions within the middle intertidal

What abiotic factor mostly determines how high barnacles can live in the middle intertidal zone? What two biotic factors mostly determine how low they can live?

The abiotic factor which determines how high barnacles can live in the middle intertidal zone is exposure to air. The two biotic factors which determine how low they can live are competition with other creatures for living space and the threat of predators.

In the middle intertidal zone of a rocky intertidal beach, a large area is found to have mostly chitons feeding on macroalgae growing there. Would this be considered a climax community?


In the middle intertidal, one rock is covered with mussels, while another is covered with algae. Which boulder was more recently cleared of its living organisms?

The one covered with algae.

Which zone of the rocky intertidal has the greatest diversity of organisms- the upper, middle, or lower?


What is the limiting resource (or resources) of each of the three intertidal zones? What are the dominant organisms in each.

Upper- Limiting resource is water and dominate organisms are cyanobacteria and lichins
Middle- Limiting resource is space/air and the dominating organisms are barnacles
Lower- Limiting resource is light and dominating organisms are sea stars

Place these sediment types in order from smallest to largest: sand, silt, and clay. Which two materials make up "mud?"

Clay and silt

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

Areas of mud and clay have less oxygen. Therefore, organisms living in the muddy intertidal must bury themselves within reach of the surface

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

There is more detritus than anything else

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

Sandy zonation.

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