Oxygenic photosynthesis made possible the accumulation of oxygen in Earth's atmosphere and oceans. The primary producers of oxygen as of 800 million years ago that power the modern carbon cycle are:
A. cyanobacteria.
B. anoxygenic phototrophs.
C. algae and plants.
D. purple bacteria.
C
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What is the most widespread extractive seafloor mining operation?
a. Sulfides b. Sand and gravel c. Salt and water d. Manganese nodules
Factors which provide a measure of biodiversity in a particular ecosystem include
A) the total number of species in that ecosystem B) the variability of the individual genes C) the relative abundance of each species D) the number of different habitats being utilized E) All of the choices are correct.
Darwin's main tenet of natural selection was
A. that only the oldest live to reproduce. B. only those that are most suited to the conditions at the time survive to reproduce. C. every organism has the potential to produce more offspring than can survive. D. Both A and B are correct. E. Both B and C are correct.
Transcription begins near a site in the DNA called the
A. promoter B. transcription unit C. enhancer D. regulatory sequence E. response element