Keystone species involve _______.
a) species that have disproportionately large effects relative to their abundance
b) certain small areas that hold unusually large number of species
c) two species which cannot occupy the same niche in a habitat
d) nonnative species introduced into a new ecosystem that cause native species to go extinct
Answer: a) species that have disproportionately large effects relative to their abundance
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Archaea is divided into three phyla
Indicate whether the statement is true or false.
A 4-year-old boy attended day care 3 days per week. He was irritable, and his parents noticed that he had persistent perianal itching. A sticky paddle was pressed against the perianal region and sent to the laboratory for testing. The eggs microscopically observed would most likely have which one of the following morphologic features?
a. Long with a short buccal cavity b. Thin shell with internal granules c. Bipolar plugs d. Flat-sided, football-shaped
Of the following sequences, which one reflects the best scientific knowledge about the succession of Homo species from the past until the present?
A. Homo heidelbergensis ® Homo habilis ® Homo sapiens ® Homo erectus B. Homo habilis ® Homo heidelbergensis ® Homo erectus ® Homo sapiens C. Homo heidelbergensis ® Homo sapiens ® Homo erectus ® Homo habilis D. Homo sapiens ® Homo heidelbergensis ® Homo habilis ® Homo erectus E. Homo habilis ® Homo erectus ® Homo heidelbergensis ® Homo sapiens
Each DNA nucleotide is composed of ____
a. a six-carbon sugar, a phosphate group, and one of twenty amino acids b. a five-carbon sugar, a nitrogenous base, and one of twenty amino acids c. a five-carbon sugar, a phosphate group, and one of four nitrogenous bases d. a six-carbon sugar, a nitrogenous base, and one of four amino acids e. a five-carbon sugar, a phosphate group, and one of four amino acids