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Biology LibreTexts

51: Algae

Objectives

  • Recognize major groups of the algae
  • Identify some common species of algae

CLASSES OF ALGAE 

Algae fall into 2 kingdoms, Protista for the single-celled algae and Planta for the multicellular algae. Since microbiology is the study of single-cells microscopically small organisms, it is fitting that we look at a few algae, those in the Protista kingdom. The algae all have a couple of things in common---photosynthesis and chlorophyll pigment, but there are many differences among the various classes of algae. They can have other pigments in addition to chlorophyll, various storage molecules, unique walls, motility structures, and so on.

In this lab, you will look at 3 classes (there are at least 3 more classes of algae):

  • Euglenoids -motile, flagellated protozoan-like algae (Euglena)
  • Golden algae (diatoms) - xanthophyll pigments give them a yellowish coloration (diatoms)
  • Green algae - precursers of plants (Volvox, Spirogyra, desmids)

In addition, we also have a NON-algal organism called Anaebena which is actually a kind of photosynthetic bacterium in the group of cyanobacteria. It is lumped into this algae lab because 1) it is pigmented, and 2) the cyanobacteria used to be called blue-green algae (cyano = "blue-green").

 

MATERIALS NEEDED

  • pond water
  • cover slips
  • prepared slides or fresh specimens of:
    • Volvox
    • Euglena
    • Anabaena
    • Spirogyra
    • diatoms of various species

THE PROCEDURE

  1. Make wet mounts of the various species of algae.
  2. Use 10X, maybe 40X, magnification.
  3. Once you have found them on brightfield, switch over to darkfield and phase-contrast. You will see much better contrast and a much more interesting organism with these 2 kinds of microscopy.
  4. You might want to draw these algae since THERE ARE NO PICTURES of algae in your Photo Atlas.

QUESTIONS

  1. Name a criterion or feature used to categorize the algae into different groups.
  2. Why were the Cyanobacteria renamed from the previous name 'blue-green algae?

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