Groups of Protists

Free Response

The chlorophyte (green algae) genera Ulva and Caulerpa both have macroscopic leaf-like and stem-like structures, but only Ulva species are considered truly multicellular. Explain why.

Hint:

Unlike Ulva, protists in the genus Caulerpa actually are large, multinucleate, single cells. Because these organisms undergo mitosis without cytokinesis and lack cytoplasmic divisions, they cannot be considered truly multicellular.

Why might a light-sensing eyespot be ineffective for an obligate saprobe? Suggest an alternative organ for a saprobic protist.

Hint:

By definition, an obligate saprobe lacks the ability to perform photosynthesis, so it cannot directly obtain nutrition by searching for light. Instead, a chemotactic mechanism that senses the odors released during decay might be a more effective sensing organ for a saprobe.

Opisthokonta includes animals and fungi, as well as protists. Describe the key feature of this phylum, and an example of how an organism in each kingdom uses this feature.

Hint:

The key feature of Opisthokonts is the flagellum on the posterior end of cells.

Example organisms:

  • Choanoflagellates use the flagellum for filter feeding.
  • Sponges (animals) use the flagellum for filter feeding.
  • Male gametes (animals) use the flagellum for locomotion.
  • Fungi spores use the flagellum for locomotion.

Describe two ways in which paramecium differs from the projected traits of the last eukaryotic common ancestor.

Hint:

Possible answers include:

  • Two nuclei (a macronucleus and a micronucleus) instead of one nucleus
  • Amitotic division/binary fission during asexual reproduction instead of mitotic cell division
  • Mitosis of the micronucleus after meiosis instead of direct meiotic production of gametes for sexual reproduction