12.3: Protists
- Page ID
- 133697
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)While bacteria are simple prokaryotes, protists are more complicated eukaryotic organisms. Protists are extremely diverse in their choice in nutrition, environment, and appearance. They may be unicellular or colonial. Many do not harm humans but some are responsible for diseases such as malaria and African sleeping sickness. Some are important nutrient recyclers and some are used to help treat our wastewater. In essence, the protists belong in a “junk drawer” in that they are so different from each other but are classified together as they do not belong to any other group.
Let’s introduce a few of the protist groups we will look at in this exercise. Below is a list of different types of protists and the organisms they are similar to.
Protozoa - single celled animal-like protists
Algae - plant-like protists
Slime molds - fungus-like protists
Protozoans
Protozoans are protists that are single-celled and heterotrophic, meaning that they consume other biological compounds. This can mean that they are predators, detritivores, or decomposers. Even though the protozoans are similar to animals, they do not meet all of the criteria to be part of Kingdom Animalia, hence their separation.
Protozoans can move around using structures such as cilia, flagella, or pseudopodia. Below is a table describing each of these methods of movement.
| Structure | How It Provides Movement |
|---|---|
| Cilia | Many short cilia move together to move the protozoan. They can also be used to guide food in towards the cell. |
| Flagella | 1-2 flagella move in a wave- or oar-like pattern to generate movement. |
| Pseudopodia | Parts of the cell protrude forward to allow the protozoan to “crawl” along the surface. These protrusions can also be used to engulf materials such as food particles. |
Let’s look at a few preserved protozoans under the microscope.
Paramecium
What mode of locomotion does the Paramecium specimen use?
Amoeba
What mode of locomotion does the Paramecium specimen use?
Algae
Algae are another type of protist. Algae may be unicellular, colonial, filamentous, or multicellular. Algae generally are aquatic and photosynthetic. Even though they are similar to plants, they do not meet the criteria of the Kingdom Plantae. When we classify algae, we base that classification on two things – color and complexity. Below is a table explaining these classifications.
| Green | Brown | Golden-Brown | Red |
| Unicellular | Algae lives on their own as a single cell |
| Colonial | Algae cells live together in a cluster, but individual cells can also live independently |
| Filamentous | Algae consists of long chain of cells, but individual cells can also live independently |
| Multicellular | Algae consists of cells that may be specialized and form structures such as a holdfast or blade |
Now, let’s observe several algae specimens. Some will require the use of a microscope while others are visible to the naked eye.
Chlamydomonas
To which of the 4 color categories does Chlamydomonas belong?
To which of the 4 complexity categories does Chlamydomonas belong?
Spirogyra
To which of the 4 color categories does Spirogyra belong?
To which of the 4 complexity categories does Spirogyra belong?
Ulva
To which of the 4 color categories does Ulva belong?
To which of the 4 complexity categories does Ulva belong?
Diatoms
To which of the 4 color categories do diatoms belong?
To which of the 4 complexity categories do diatoms belong?
Red algae
To which of the 4 color categories does red algae belong?
To which of the 4 complexity categories does red algae belong?
Euglenoids
Some protists still don’t fit even into these categories! Our last microorganism is Euglena, which shows characteristics of both protozoans and algae. Euglena are freshwater protists that are able to photosynthesize like algae. They also have flagella and lack a cell wall like protozoans. They even have an eyespot to detect light.
Euglena
How does the eyespot help the Euglena? Hint: think about Euglena’s capabilities.