Explain why today's estimate of the number of species present on Earth is so uncertain
What will be an ideal response?
One reason for the uncertainty in the estimate of today's global species number is because some areas of Earth remain largely unexplored, with scientists doing detailed sampling only in small areas and using those data to estimate what would be expected across larger areas. Another reason is that many species are tiny and easily overlooked; these inconspicuous organisms include insects, soil-dwelling organisms, and microorganisms such as bacteria. Global estimates range from 5 to 100 million species, but only 1.75 million species have been identified and named.
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Global warming is caused by increased concentrations of ____________________ in the atmosphere Fill in the blank(s) with the appropriate word(s)
Which of these factors influences the sensation of temperature that the human body feels?
A) air temperature B) humidity C) wind speed D) all of the above
Changes in the Earth's elliptical orbit around the Sun is called
A) eccentricity. B) obliquity. C) precession. D) inclination.
Choose the correct historical sequence of fuel use in the U.S. from 1800 to the present.
A. oil, wood, coal, gas B. wood, oil, coal, gas C. coal, wood, gas, oil D. wood, coal, oil, gas