Which gas began to increase in the atmosphere as a result of photosynthesis by autotrophic prokaryotes approximately 2.7 billion years ago?
A) methane
B) carbon dioxide
C) oxygen
D) hydrogen
C) oxygen
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Why can't a female lizard have both high fecundity and high survival?
A) In only rare cases, lizards have both high fecundity and high survival. B) Female lizards are able to produce only one set of offspring. C) Competition for resources prevents this. D) The more energy the female devotes to offspring, the less that can be devoted to her survival. E) The female is already maximizing the number of eggs she lays, and if she attempts to nest later in the season, there will not be enough food for her young.
Loading of most carbohydrates produced by photosynthesis into companion cells at a source occurs by ____
a. osmosis b. proton pumping c. suction from unloading at a sink d. active transport e. diffusion of water from the xylem
What results would you expect if mitochondria are inherited uniparentally from the a strain?
A) Some, but not all, yeast colonies found on the plate without chloramphenicol will also grow on the plate with chloramphenicol. B) All of the yeast colonies on the plate without chloramphenicol will also grow on the plate with chloramphenicol. C) Many yeast colonies will grow on the plate without chloramphenicol and no colonies will grow on the plate with chloramphenicol. D) No colonies will grow on either plate.
In a 3-D double helix model of DNA, the center consists of ____
a. deoxyribose sugars b. hydrogen bonds c. nucleotide base pairs d. phosphate groups e. sugar–phosphate backbones