The loss of mayflies from a stream suggests that the quality of water is declining; therefore, mayflies are a(n) ____ species.
a. degraded
b. endangered
c. threatened
d. keystone
e. indicator
ANSWER: e
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Tissues of sharks are isotonic to seawater, but their concentrations of sodium ions, potassium ions, and chloride ions in cells and extracellular fluids are similar to those of freshwater fishes. What can you infer about the movement of sodium and chlorid
A) To maintain homeostasis of sodium and chloride levels, the shark must take up additional sodium and chloride from seawater. B) Sodium and chloride will diffuse into shark gills from seawater down their concentration gradient. C) Sharks conserve sodium and chloride, limiting excretion. D) Sodium and chloride must be eliminated through the gills.
Mycorrhizal fungi can either be intracellular or extracellular.
Answer the following statement true (T) or false (F)
Recent research has suggested that some pseudogenes and non-protein-coding DNA code for RNAs that affect transcription of coding regions. This suggests that
A. non-protein-coding DNA has no function. B. non-protein-coding DNA may regulate gene expression. C. pseudogenes code for proteins. D. pseudogenes have no function.
Network of DNA strands and associated proteins observed within a nucleus of a cell.
What will be an ideal response?