At the end of the Ordovician, many shallow-marine organisms went extinct due to
A) deep water predators.
B) a long duration of high sea level.
C) cooling temperatures, increased glaciation, and decreased sea level.
D) cooling temperatures, increased glaciation, and a rise in sea level.
Answer: C
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An atom that has lost or gained one or more electrons is called a(n) ____
a. ion b. isotope c. nucleus d. molecule e. electron
If we could watch spiral arms from a telescope situated above the Milky Way over 500 million years, what would we see happen?
A) Stars will move through the spiral arms, bunching up closer as they pass through. Young hot stars will form and die within the arms before having a chance to move out. B) The spiral arms will eventually unwind, as centripetal forces send the stars flying outwards into intergalactic space. C) The spiral arms will eventually dissipate and fade away, since they are a temporary phenomenon that should only last for a million years or so. D) The spiral arms will seem to "wind up," to wrap more and more tightly around the center of the Galaxy.
If atmospheric refraction did not occur, how would the apparent time of sunrise and sunset be changed?
a. Both would be later. b. Both would be earlier. c. Sunrise would be later and sunset earlier. d. Sunrise would be earlier and sunset later.
Thermodynamic Devices: Suppose that the Department of Energy develops a new reversible engine that has a coefficient of performance (COP) of 4.0 when operated as a refrigerator and a COP of 5.0 when operated as a heat pump. What is its thermal efficiency when operated as a heat engine doing work?
A. 10% B. 20% C. 25% D. 45% E. 80%