Which of the following factors may be directly responsible for maintaining a sharp edge between prairies and forests in the midwestern United States?
A) summer drought
B) low winter temperatures
C) tornadoes
D) fire
Answer: D) fire
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The major difference between gram-positive and gram-negative bacteria is that:
a. the peptidoglycan layer in gram-positive bacteria is substantially thinner than in gram-negative bacteria. b. gram-positive bacteria contain a periplas-mic space, whereas gram-negative bacteria do not. c. flagella are only present in gram-positive bacteria. d. gram-negative bacteria contain an outer membrane that functions as the cell's ini-tial barrier to the environment.
Ecologists determined that, regardless of the richness
of the ecosystem, energy passes through no more than __________ trophic levels. a. one or two b. two or three c. three or four d. four or five e. five or six
What type of mutation commonly affects CpG islands, altering promoter regions of mammalian genes?
What will be an ideal response?
Sharks excrete a small volume of dilute urine
____________________ Indicate whether the statement is true or false.