Describe the observational differences between long-period and short-period comets
What will be an ideal response?
Most comets have long, elliptical orbits with periods greater than 200 years and are known as long-period comets. The long-period comet orbits are randomly inclined to the plane of the solar system, so those comets approach the inner solar system from all directions. Long-period comets revolve around the Sun in about equal numbers in prograde orbits (the same direction in which the planets move) and retrograde orbits. In contrast, about 100 or so of the 600 well-studied comets have orbits with periods less than 200 years. These short-period comets usually follow orbits that lie within 30 degrees of the plane of the solar system, and most revolve around the Sun prograde.
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Which of the following is the primary assumption made by researchers when designing experiments to
model how life may have arisen?
a. The chemical reactions of living things are only possible in living systems. b. Living organisms are composed of elements commonly found in the universe and on Earth. c. Conditions on Earth have not changed over time. d. Life arose on Earth from non-living matter. e. The development of living cells from nonliving matter was very rapid.
The ____________________ is the noncellular structure between an epithelium and the underlying connective tissue. Fill in the blank(s) with the appropriate word(s)
The by-product of the metabolism of cyanobacteria that had the most effect on the further evolution of life is ____.
A. oxygen gas B. carbon dioxide C. water D. nitrogen gas E. hydrogen gas
"Rice water stools" are characteristic of
A) salmonellosis. B) cholera. C) bacillary dysentery. D) amebic dysentery. E) tapeworm infestation.