Seaweeds are any of a large number of marine benthic algae. They are macroscopic, multicellular, and macrothallic, in contrast with most other algae. Seaweeds are often confused with other photosynthetic organisms. Seaweeds are popularly described as plants, but biologists typically do not consider them true Plantae. They should not be confused with plants such as seagrasses (which are vascular plants). In addition, a few species of cyanobacteria bear a resemblance to seaweed algae. Many phycologists prefer the term "marine algae" over "seaweeds".
Seaweeds' appearance somewhat resembles non-arboreal terrestrial plants.
Thallus: the algal body
lamina: a flattened structure that is somewhat leaf-like
sorus: spore cluster
on Fucus, air bladders: float-assist organ (on blade)
on kelp, floats: float-assist organ (between lamina and stipe)
stipe: a stem-like structure, may be absent
holdfast: specialized basal structure providing attachment to a surface, often a rock or
another alga.
The stipe and blade are collectively known as fronds.
2. Where is it found?
Seaweed is often found on the seashore.
3. What is the organ of attachment to the substratum called? How does it differ from a true root?
4. How does size vary in marine algae?
5. Name the four groups of marine algae, indicating opposite the name of each group whether it is unicellular, multicellular, or both.
6. Is most green algae found in fresh or salt water?
7. What are diatoms?
8. Where does algae grow-the polar, temperate, or tropic zone?
9. Where is brown algae most invariably found-in fresh or salt water?
10. What is the greatest depth that algae grows in the ocean? Why can it not grow in deeper water?
11. Name the three parts of a large kelp. How do they compare to the leaf, stem, and root of a plant?
12. Describe the two ways that algae reproduce.
13. What are some of the commercial values of algae? Give at least one for each group.
14. Make a collection of at least twenty specimen of marine algae properly identified, mounted, and labeled. There must be at least four specimens from the Green group, eight from the Brown group, and eight from the Red group.
15. Be able to identify by generic name at least ten types of marine algae.
