Texas A&M University (TAMU) BIOL112 Introductory Biology II Lab Exam 1 Practice Exam

Rhizarians are a diverse group of eukaryotic microorganisms, primarily characterized by their amoeboid forms and the presence of a unique type of shell or protective covering. Radiolarians are an excellent example of Rhizarian organisms, distinguished by their intricate silica-based skeletons and their role in marine ecosystems as both predators and contributors to the biological carbon pump.

These organisms typically possess long, radiating pseudopodia that extend from their central body, helping them both in capturing prey and in buoyancy. The silica skeletons not only provide structural support but also help scientists study past marine environments through sediment samples.

The other options presented do not belong to the Rhizarians. Plasmodium is a genus of parasitic protozoans known for causing malaria, Achyla is a genus related to water molds, and Euglena is a genus of flagellated protists often associated with both plant and animal traits. Therefore, Radiolarians exemplify the defining characteristics of Rhizarian organisms effectively.