Many closely related duck species exhibit ____, the dramatic variation in the appearance of males but not females,
which is an almost certain sign of ____.
a. asexual reproduction; sexual selection
b. asexual reproduction; artificial selection
c. sexual dimorphism; sexual selection
d. sexual dimorphism; artificial selection
e. sexual uniformitarianism; sexual selection
ANSWER: c
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Answer the following statements true (T) or false (F)
1. Plants are unable to use nitrogen gas directly. 2. Nitrate reductase is an enzyme that changes nitrogen gas into nitrate. 3. When stomata are closed plants CANNOT absorb CO2, therefore photosynthesis is limited. 4. Nitrogen is especially important in plants for the formation of proteins. 5. Certain fungi help make available minerals such as nitrogen.
Late log phase of the bacterial growth curve
A. is marked by the production of primary metabolites. B. is marked by the production of secondary metabolites. C. is a transition into the death phase. D. shows a decline in cell numbers.
__________ is one form of learning that happens only during a sensitive period early in life. Fill in the blank(s) with the appropriate word(s)
Any organism that causes disease is classified as a(n)
a. fomite. b. biological vector. c. mechanical vector. d. pathogen e. antigen.