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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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
Sharks excrete a small volume of dilute urine
____________________ Indicate whether the statement is true or false.
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.
What type of mutation commonly affects CpG islands, altering promoter regions of mammalian genes?
What will be an ideal response?