Two species of squirrels live on either side of the Grand Canyon. It is believed that a long time ago, before being separated by the canyon, they were the same species. This is an example of
A) mechanical isolation.
B) temporal isolation.
C) hybrid inviability.
D) behavioral isolation.
E) allopatric speciation.
E
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When two frog species, Rana pippins and Rana sylvatica, mate, the offspring die early in embryonic development. This is an example of ___________.
A. Hybrid sterility B. Reduced hybrid fertility C. Mechanical isolation D. Reduced hybrid viability
Which group of algae are economically useful, serving as the source of carrageenan and agar?
A) Euglenozoa B) Chlorophyta/Chloroplastida C) Rhodophyceae D) Alveolata
Which of the following is an example of positive feedback?
A) After eating a meal containing high glucose levels, the pancreas secretes more insulin, a hormone that lowers blood glucose levels. B) After cutting your finger, the injured tissue releases chemicals that activate platelets in the blood. These activated platelets release chemicals to activate more platelets, leading to the formation of a blood clot. C) An elevation in blood pressure causes heart rate to decrease, thereby causing blood pressure to decrease. D) The secretion of the hormone TSH stimulates the thyroid gland to secrete thyroxine. Thyroxine, in turn, inhibits the secretion of TSH.
Most RNA viruses carry which of the following enzymes?
A) DNA-dependent DNA polymerase B) lysozyme C) RNA-dependent RNA polymerase D) reverse transcriptase E) ATP synthase