How has the average per capita world fish catch changed over the last several decades?
A) It has been climbing steadily since the 1950s.
B) After declining in the 1960s, it has increased sharply since 1970.
C) It has stayed at 1960 levels.
D) It increased steadily to about 1970, and then declined.
D
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Large, angular class are most likely at
a) glaciers at B and braided river at C b) mountains at A and glaciers at B c) delta at D and lake at E d) braided river at C and delta at D
The amount of biomass on successive trophic levels in a food chain forms a pyramid in which the biomass on trophic level N+1 is only 20% of the biomass on trophic level N. If pesticide P is transferred from one trophic level to the next with 100% efficiency, what will be the concentration of P on trophic level 5 if the concentration of P on trophic level 2 is 4 parts per million (ppm)?
a. 500 ppm b. 2500 ppm c. 20 ppm d.100 ppm
A deposit of loose sand may have a porosity of ________ percent.
A. 40-50 B. 30-50 C. less than 20 D. 20-30 E. more than 50
What do Eurasian milfoil, kudzu vine and the emerald ash borer have in common?
A. They are exotic species wreaking havoc in the ecosystems into which they have been introduced B. They offer exciting prospects as potential sources of new drugs C. They are all in danger of extinction in their native habitats D. They offer promise as agents of biological control for pest species