Why have plants been implicated in the Ordovician and Devonian glaciations, but not the Proterozoic glaciations?
A. Land plants had not yet evolved during the Proterozoic.
B. Proterozoic plants had simple root structures that did not increase rock weathering.
C. Proterozoic plants used anoxygenic photosynthesis.
D. The nonvascular plants present during the Proterozoic did not contribute to global nutrient cycles.
Answer: A
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excreted? A) Pyruvate export requires more energy than lactate. B) Electrons (and protons) are added to pyruvate to make lactate. C) NAD+ is regenerated as pyruvate is changed to lactate. D) Substrate level phosphorylation changes pyruvate to lactate. E) both choices B and C
Which of the following can serve as channels or pumps within the cell membrane?
a. integral proteins b. glycoproteins c. cholesterol d. phospholipids
Which hormone increases blood-glucose levels?
a. cortisol b. glucagon c. insulin d. epinephrine
Which of the following is a defining trait found in chordate embryos?
a. a pseudocoelom b. a larval stage c. a coelom d. limb buds e. gill slits