A stream flows through marshes, farmland, and suburban housing developments before emptying into the ocean. Describe three ways in which the different land areas along its course affect the water quality of the stream.
What will be an ideal response?
Water flow will differ in each area and directly affects the oxygen level in the water, i.e., low flow areas will have less dissolved oxygen. Marsh areas will have limited flow and limited flow may result in low levels of dissolved oxygen. Farms may use pesticides for crops or they may have animals that produce waste, both of which will lead to contamination. In suburban areas, water quality may be affected by sewage run-off, pollution, or chemical waste.
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Which two cell scientists are credited with the formulation of the cell theory, also known as the cell doctrine?
A. Watson and Crick B. Schleiden and Schwann C. Schleiden and Hooke D. Schwann and Jenner
In your Drosophila laboratory, you find a larva that is missing segments Lb, T1, T2, and T3. This larva probably has a mutation in a ___________ gene.
A. pair-rule B. gap C. maternal effect D. segment-polarity E. gap or segment-polarity
While studying a protein synthesized by human liver cells, you notice a correlation between stress and decreased levels of this protein. Initially, you hypothesized that stress caused phosphorylation of eIF-2, and a commensurate reduction in protein synthesis, but further investigation revealed that the rate of synthesis of this protein had not changed—there simply was not as much within the cells as expected, nor was the protein being secreted by the cells. What possible explanation remains?
a. Stress alters the protein structure making it undetectable. b. Stress weakens the polypeptide bonds in this protein. c. Stress causes ubiquitin to bond to the protein. d. Stress causes eIF-2 to hydrolyze the protein.
A microorganism that does not have catalase or superoxide dismutase would find it difficult to live in an environment with ________.
A. carbon dioxide B. high salt C. temperatures above 37° C D. oxygen E. high acidity