AY Honors/Marine Algae/Answer Key

1. What is marine algae?

The most common name for marine algae is "seaweed". Seaweeds are popularly described as plants, but biologists do not consider them plants (in biology, all true plants belong to the kingdom Plantae). They should not be confused with aquatic plants such as seagrasses (which are vascular plants).

2. Where is it found?

Marine algae are mostly found in shallow ocean water near rocky shores.

3. What is the organ of attachment to the substratum called? How does it differ from a true root?

The organ that attaches a marine algae to a substrate is called a "holdfast" Unlike a root, a holdfast derives no nutrients from this intimate contact with the substrate..

Holdfasts vary in shape and form depending on both the species and the substrate type. The holdfasts of organisms that live in muddy substrates often have complex tangles of root-like growths, while those of organisms that live in sandy substrates are bulb-like and very flexible, such as the holdfast of sea pens, allowing the organism(s) to pull the entire body into the substrate when the holdfast is contracted. The holdfasts of organisms that live on smooth surfaces (such as the surface of a boulder) have the base of the holdfast literally glued to the surface.

4. How does size vary in marine algae?

Some marine algae are so small they can only be seen under a microscope. Others are very large, such as Macrocystis, a species of kelp belonging to the brown algae group, which may reach 60 meters in length.

5. Name the four groups of marine algae, indicating opposite the name of each group whether it is unicellular, multicellular, or both.

Group	Unicellular	Multicellular
Red Algae
Brown Algae
Green Algae
Diatoms

8. Where does algae grow-the polar, temperate, or tropic zone?

Algae grow in all of these zones, from Picobiliphytes, which are an algae indigenous to polar regions, to Sargassum, which lives in the tropical waters of the Atlantic Ocean.