The sea snail, Littorina saxatilis, is found on the coast of northern Spain. The snails farther upshore are large, with heavily ridged and banded shells, and share a border with the snails farther downshore that are smaller with smooth, unbanded shells. If the upshore and downshore snails became separate species, this would be an example of speciation.

A. sympatric
B. parapatric
C. allopatric
D. prezygotic
E. postzygotic


B. parapatric

Biology & Microbiology

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The ________ (enzymes) link amino acids with their appropriate tRNAs.

Fill in the blank(s) with the appropriate word(s).

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Some scientists predict that as atmospheric carbon dioxide levels increase, plant growth will also increase. What is the best explanation for this hypothesis?

A. Plants release carbon dioxide into the atmosphere during respiration. B. Plants consume carbon dioxide from the atmosphere during photosynthesis. C. Plants consume carbon dioxide from the atmosphere during respiration. D. None of the answer choices is correct. E. Plants release carbon dioxide into the atmosphere during photosynthesis.

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Which of the following is NOT a characteristic of

some mollusks? a. radula b. mantle c. gills d. pseudocoel e. shell

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Biology & Microbiology