How can researchers confirm that phloem moves from a source to a sink?
A. They can use radioactive tracers to measure the flow of sap between two distances over time.
B. They can study the cause of maple sap flow in producing syrup.
C. They can observe the uptake of ink into the stem of celery.
D. They can observe aphids and cut off their beaks.
E. They can observe the effects of girdling a tree below the level of the majority of leaves.
Answer: E
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In many species, there are two representatives of each chromosome. In such species, the characteristic number of chromosomes is called the ________ number. It is usually symbolized as ________
A) haploid; n B) diploid; n C) diploid; 2n D) haploid; 2n E) None of the answers listed is correct.
In order to visualize the fine structure of viruses and cytoskeletal filaments at 10-25 nanometers in diameter the type of microscopy that would be most effective is
A. transmission electron microscopy. B. standard light microscopy. C. differential-interference microscopy. D. phase-contrast light microscopy. E. darkfield light microscopy.
Sympatric speciation differs from allopatric speciation because with sympatric speciation
A. a population becomes geographically isolated. B. two populations of the same species merge to form a single population. C. polyploidy (changes in the number of sets of chromosomes) arises. D. hybrid zones form. E. temporal factors may arise without geographic isolation occurring and polyploidy may arise.
As the magnification of a series of objective lenses increases, the working distance
A. decreases. B. stays the same. C. increases. D. cannot be predicted.