What percentage of the world's photosynthetic activity is accomplished by phytoplankton in the euphotic zone?
A. 70
B. 60
C. 50
D. 40
E. 30
Answer: D
You might also like to view...
A ________ is a one-sided fold connecting horizontal or gently inclined strata.
A) syncline B) overthrust C) symmetrical fold D) anticline E) monocline.
Which of the following is true of a 100-year flood?
A) A 100-year flood occurs every 100 years on a given stream. B) The probability of a 100-year flood occurring on any given year is 1:100. C) A 100-year flood cannot occur twice within 10 years. D) The probability of a 100-year flood is related to how recently the last 100-year flood occurred.
The third-most abundant gas in Earth's atmosphere (not including water vapor) is
A) oxygen. B) argon. C) nitrogen. D) carbon dioxide. E) helium.
Coral bleaching occurs when
a. corals reproduce. b. fish move into coral reefs. c. zooxanthellae (algae) leave the coral. d. coral reefs expand their range.