Diazotrophs maximize nitrogenase activity by
A) closely coupling N2 fixation with high rates of photosynthesis.
B) fixing N2 at times when oxygen is absent or in low concentrations.
C) producing specialized structures to protect nitrogenase from oxygen.
D) producing specialized structures or fixing N2 at times when oxygen is absent to protect nitrogenase from oxygen.
Answer: D
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When observing the skeleton of a snake, you see the remains of hip and hind leg bones associated with four legged animals. These bones are called
A. convergent traits. B. analogous structures. C. vestigial structures. D. homologous structures. E. both homologous and analogous structures.
A scientist makes three artificial mRNA strands: (x) 5' AAAUUUAAAUUUAAAUUUAAAUUUAAA 3'(y) 5' UUUCCCUUUCCCUUUCCCUUUCCCUUU 3'(z) 5' AUAUAUAUAUAUAUAUAUAUAUAUAU 3'When he analyzes the polypeptides produced, he finds that:x produces a polypeptide that is 50% phenylalanine and 50%lysine.y produces a polypeptide that is 50% phenylalanine and 50% proline.z produces a polypeptide that is 50% isoleucine and 50% tyrosine.Based on these results only, the best conclusion to make is that
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______ are molecules that stimulate a response by T and B cells.
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