Fill in the blanks on the phylogenetic tree (on the facing page) to show current hypotheses for the origin of multicellular organisms.
Ch. 16 Microbial Life: Prokaryotes and Protists
Taylor, Simon, Dickey, Hogan10th EditionCampbell Biology: Concepts & ConnectionsISBN: 9780136538783Not the one you use?Change textbook
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Taylor, Simon, Dickey, Hogan 10th Edition
Ch. 16 Microbial Life: Prokaryotes and Protists
Problem 5
Taylor, Simon, Dickey, Hogan 10th Edition
Ch. 16 Microbial Life: Prokaryotes and Protists
Problem 5Chapter 16, Problem 5
Which pair of protists has support structures composed of silica?
a. Dinoflagellates and diatoms
b. Diatoms and radiolarians
c. Radiolarians and forams
d. Forams and amoebozoans
Verified step by step guidance1
Understand the question: The problem is asking which pair of protists has support structures composed of silica. Silica is a mineral commonly found in the cell walls or skeletons of certain protists.
Recall the characteristics of diatoms: Diatoms are a type of protist that have cell walls made of silica, forming intricate and beautiful patterns. This is a key feature of diatoms.
Recall the characteristics of radiolarians: Radiolarians are another type of protist that have internal skeletons composed of silica. These skeletons are often elaborate and contribute to their structural support.
Eliminate incorrect options: Dinoflagellates do not have silica-based structures; they typically have cellulose plates. Forams have calcium carbonate shells, not silica. Amoebozoans lack silica-based support structures entirely.
Identify the correct pair: Based on the information above, the pair of protists with silica-based support structures is diatoms and radiolarians.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Diatoms
Diatoms are a group of microalgae characterized by their unique silica cell walls, which form intricate and beautiful patterns. These cell walls, known as frustules, provide structural support and protection, allowing diatoms to thrive in various aquatic environments. Their silica composition is crucial for their identification and ecological role in primary production.
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Radiolarians
Radiolarians are single-celled protists that possess intricate silica skeletons, which can take on various geometric shapes. These skeletons not only provide structural support but also contribute to the formation of siliceous ooze on the ocean floor when they die. Radiolarians play a significant role in marine ecosystems and biogeochemical cycles.
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Silica as a Support Structure
Silica, a compound made of silicon and oxygen, is a key component in the support structures of certain protists, such as diatoms and radiolarians. This material provides rigidity and protection, allowing these organisms to maintain their shape and survive in diverse environments. The presence of silica in their structures is a defining characteristic that aids in their classification and ecological function.
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Related Practice
Textbook Question
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Textbook Question
In terms of nutrition, autotrophs are to heterotrophs as
a. Kelp are to diatoms.
b. Archaea are to bacteria.
c. Slime molds are to algae.
d. Algae are to slime molds.
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Textbook Question
A new organism has been discovered. Tests have revealed that it is unicellular, is autotrophic, and has a cell wall that contains peptidoglycan. Based on this evidence, it should be classified as a(n)
a. Alga.
b. Archaean.
c. Protist.
d. Bacterium.
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Textbook Question
Which of the following members of the SAR supergroup is incorrectly paired with its clade?
a. Stramenopiles—brown algae
b. Alveolates—parasites such as Plasmodium
c. Alveolates—dinoflagellates
d. Rhizaria—diatoms
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Textbook Question
Which of the following prokaryotes is not pathogenic?
a. Chlamydia
b. Rhizobium
c. Streptococcus
d. Salmonella
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Textbook Question
Explain why prokaryote populations can adapt rapidly to changes in their environment.
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