Molecular-based phylogies place the phylum Platyhelminthes in the Protostomia. How do scientists best explain the morphological differences between flatworms and the other members of the Lophotrochozoa?
A. Modern Platyhelminthes do not have a coelom but did originate from an ancestor that had one.
B. The Platyhelminthes clade separated from other clades before coeloms evolved and consequently Platyhelminthes have never had a coelom.
C. Platyhelminthes originated from ancestors with a coelom and have retained it to the present time.
D. Platyhelminthes evolved from an ancestor without a coelom but developed one during the course of their evolution.
E. Some Platyhelminthes have a coelom but others do not and it is difficult to conclude anything about its evolution within the clade.
A. Modern Platyhelminthes do not have a coelom but did originate from an ancestor that had one.
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Select the best response to the question. Why are prions a concern for health care providers?
A) Large numbers of new prion-related diseases are diagnosed each year. B)Prion-related diseases require multiple medications for successful treatment. C)Prions are resistant to a number of routine sterilization techniques. D) Prion-related diseases cause severe cardiopulmonary (heart)-related signs and symptoms.
A fish detects vibrations in the water by means of its ____, which contains numerous ____.
A. lateral line, hair cells B. ear, statocysts C. swim bladder, stretch receptors D. skin, mechanoreceptors E. lateral line, thermoreceptors
Chemotaxis refers to the ability of a cell to
A. move in response to a chemical. B. move in response to light. C. transport desired molecules into a cell. D. halt movement in response to a chemical.
Bacitracin
A. inhibits DNA replication. B. interferes with protein synthesis. C. inhibits peptidoglycan synthesis. D. interferes with plasma membrane function.