Algae-External Anatomy

Characteristics :

  • Plant-like organisms with very simple structure and having no roots, stems, or leaves.
  • One-celled or many-celled; if multicellular, have a single-cell embryo within female reproductive structure.
  • Cells have chloroplasts and a nucleus contained within membranes (blue-green algae is an exception).
  • Most make food using light energy (photosynthetic).
  • Are aquatic, either primarily in a body of water or in moist tissues of other organisms (some live in ice and snow and on moist soil)
The group called algae is diverse and several classification schemes exist. Below is listed a possible system of classification, taken only to the division level, for the algae.
  • Kingdom: Monera
    • Division: Cyanophyta (blue-green algae) photosynthetic bacteria
  • Kingdom: Protista
    • Division: Charophyta (stoneworts and brittleworts) Chlorophyta (green algae) Cryptophyta (cryptophytes) Chrysophyta (golden algae)
      • Class: Bacillariophyceae (diatoms)
        • Dinophyta (dinoflagellates) Euglenophyta (euglenoids) Phaeophyta (brown algae) all marine "seaweeds" Rhodophyta (red algae) most are marine, but a few are freshwater
Student Challenge:
  • Using a stream or a pond as a model, illustrate a food web that utilizes algae as a primary food source. Keep the size proportions of your organisms as accurate as you can. Use string or yarn to show how energy moves from one organism to another. Does the string in your finished illustration resemble a spider’s web? Write a paragraph showing how algae are helpful even to animals that do not feed on it directly. 
  • Using field observations, photos, or microscopic slides of algae, identify the various geometric shapes of the alga cells. If you are making field observations, try to visit several locations of the stream or pond. Draw the shapes of the algae you see in your journal. Make notes of water conditions, such as flow rate, water depth, and light intensity. Don’t forget to note the date and time of day too. Are the alga shapes always symmetrical? Is there a correlation between flow rate of the water and shape of the cells? Make a hypothesis connecting alga shape to living conditions. Present your hypothesis in the form of a poster that shows both shape and flow rate of the water. 
  • ​Much of life in an aquatic ecosystem depends upon algae to convert the sun’s energy into a form usable as food. The algae itself has certain requirements for growth. Two of these are sufficient light energy and proper temperature. Using the Scientific Method as a model, design a way to determine relationships between water depth, light energy, and temperature. Do an inventory of algae species in a small section of water near you. Record the depth at which each species was found. Develop a visual presentation showing your conclusions concerning algae growth, water depth, light energy, and temperature. Present your findings to your classmates, at a science fair, or at parent night.