Which of the following species was once considered so benign that microbiologists used it to trace movements of air currents in hospitals and over cities?
What will be an ideal response?
Serratia.
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Epidermal growth factor (EGF) secreted from an anchor cell binds to its receptor on a nearby cell and initiates signal transduction. Which statement describing this signaling pathway is not correct?
A. In response to EGF binding to its receptor, a series of protein phosphorylations occur which amplify the signal at each step. B. Certain key phosphorylated proteins enter the nucleus and act as transcription activators for the Notch gene. C. The Notch protein is a transmembrane protein that is inserted across the plasma membrane and acts as a ligand for a Notch receptor on the adjacent cell that will then become a type 2 cell. D. Transcription of the Notch ligand in the type 1 cell results in an inhibition of the Notch receptor in the type I cell and in an inhibition of the EGF receptor in the adjacent cell destined to differentiate into a type 2 cell. E. EGF and Notch ligands are unique to nematodes and only found in Caenorhabditis elegans.
Which of the following organelles contain DNA? (Select all correct choices.)
A. the nucleus B. the ribosome C. mitochondria D. chloroplasts
In vertebrates, most of the fluid that ultimately exits the body as urine first enters the nephron tubules by the process of ____________.
A. absorption B. excretion C. filtration D. reabsorption E. secretion
Biomagnification is a significant problem in aquatic communities. Levels of chemicals magnify (increase or accumulate) at each new link in a food chain. Use the following information to estimate the level of chemical X in a large-mouth bass. One alga can accumulate 1 unit of chemical X. Each copepod eats 15 algae. A minnow consumes 10 copepods, each large-mouth bass consumes 20 minnows.
A. 3,000 units B. 150 units C. 30 units D. 20,000 units E. 300 units F. 15 units G. 20 units