Notes about Protists

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Copyright © 2007-2010 by Zack Smith.
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Contents

Overview

Protists include all eukaryotes other than animals, plants and fungi, and because they are eukaryotes they are complex organisms, moreso than Bacteria or Archaea. Protists evolved just after Archaea and they descended from the early eukaryotes and around the time when the Earth saw an increase in oxygen in the atmosphere.

Protists are usually single-celled, but they can be multicellular and they can form colonies of single-cell protists, and aggregates.

Protists live in water or moist soil.

Parts of protists

Protists have a nucleus, organelles, cell membrane, a means of locomotion. Some protists can do photosynthesis because they have chloroplasts.

Variations

There is a great deal of variety in protists, such as:
  • Cell wall material
  • Means of locomotion
  • Means of getting energy
  • Pigmentation
  • Unicellular vs. colony vs. aggregate vs. multicellular
  • Means of eating other organisms, if any.

Cell wall

  • Cellulose (e.g. dinoflagellates)
  • Algin (brown algae)
  • Agar (red algae)
  • Calcium carbonate (foraminifera)
  • Silica (diatoms)

Means of locomotion

  • Flagella
  • Pseudopods ("false feet")
  • Cilia

Means of getting energy

  • Photoautotrophs = photosynthetic e.g. euglena, algae
  • Heterotrophs = eat other organisms
  • Mixotrophs = do both

Means of eating other organisms

  • Using cilia to push other organisms into a gullet, e.g. paramecium.
  • Using pseudopods to engulph other organisms.
  • Entering other cells to eat their nutrients from the inside, e.g. plasmodium.

Well known protists

  • Plasmodium = causes malaria, hides in liver & blood cells.
  • Paramecium = has gullet, anal pore, vacuoles
  • Diatoms = silica cell wall
  • Euglena = one flagellum with chloroplasts
  • Dinoflagellates = causes toxic "red tide"
  • Algae
  • Amoeba
  • Entamoeba hyperili? = causes dysentery in vertebrates
  • Foraminifera = calcium carbonate cell wall

Colonies

Some protists prefer to live in colonies, e.g. Volvox.

Aggregates

Plasmodial slime molds are actually protists and they prefer to live in close contact with one another. They come in orange and yellow.

Kinds of Algae

Algae is a type of protist that is of particular interest because of its economic value.

Green algae, AKA ulva, AKA kelp, AKA sea lettuce, has chlorophyll.

Red algae has phycobilin pigment that masks the chlorophyll. Its cell walls are made of agar.

Brown algae AKA fucus, has fucoxantan pigment. Its cell walls are made of algin.

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