GRE Subject Test: Biology : Identifying Protists

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #42 : Microorganisms And Viruses

Which of the following is not true of protists?

Possible Answers:

All protists are unicellular by definition

Protists are diverse in part due to endosymbiosis, a process by which small, unicellular organisms are engulfed by larger unicellular organisms and eventually evolve to become organelles

A "protist" is broadly recognized as a eukaryote that is not an animal, fungus, or plant

Malaria, red algae, green algae, and dinoflagellates are all examples of protists

Correct answer:

All protists are unicellular by definition


All of these answers are true, except the statement that protists are definitionally unicellular. Protists are an incredibly diverse group of organisms that are difficult to classify because of the vast differences that exist between protist species; it is easier to classify protists based on what they are not, rather than what they are. Multicellular protists include species of seaweeds called kelp. Though kelp resemble plants, they are actually multicellular groups of protists that lack true stems, roots or leaves (though kelp often have structures resembling these plant structures).

Endosymbiosis is an intriguing theory that seeks to explain the presence of complex structures such as mitochondria and chloroplasts inside of plant and animal cells. Mitochondria's similarities to free-living proteobacteria, and chloroplasts' similarities to free-living cyanobacteria suggest that at one point these structures were organisms that became engulfed by larger cells. According to the theory of endosymbiosis, mitochondria and chloroplasts lived inside their hosts in a symbiotic relationship, eventually evolving to lose their capacity to live independently and becoming organelles that support their host cell.

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