LS7B/ PCRQ 25.3 week 9

Which of the following factors likely contributed to the accumulation of O2 within Earth's atmosphere? the fact that there is a slight "de-coupling" between photosynthesis and respiration the fact that photosynthesis releases O2 as a product the fact that oxygen is also cycled during the carbon cycle All of these choices are correct. the evolution of cyanobacteria

All of these choices are correct.

Which of the following statements explains how an oxygen-rich atmosphere was possible? Rates of carbon fixation and respiration have always been equal. Photosynthetic organisms have existed on earth longer than heterotrophs. All of these choices are correct. Rates of oxygen consumption were lower than rates of photosynthesis. The number of plants has always outnumbered the animals.

Rates of oxygen consumption were lower than rates of photosynthesis.

Which of the following organisms can incorporate atmospheric carbon directly into C6H12O6, thereby playing a major role in a food web? primary producers carnivores consumers decomposers grazers

primary producers

If all of the tertiary consumers were removed from an environment, the associated food web (and thus the carbon cycle) would collapse. True False

false

Decomposers are vital components of a food web because they: immediately provide tertiary consumers with usable forms of carbon. serve as primary producers. return carbon (as CO2) to the atmosphere. incorporate the carbon contained in atmospheric CO2 into C6H12O6.

return carbon (as CO2) to the atmosphere.

The evolution of biodiversity on the planet can be linked to patterns in the carbon cycle over time. True False

true