A major difficulty facing systematists is
A) sequencing DNA.
B) distinguishing similar features due to common ancestry from those due to convergent evolution.
C) distinguishing anatomy from physiology in plant evolution.
D) understanding the sequence of cell divisions in the early embryology of plants and animals.
E) placing specimens into the predefined taxonomic categories of species and genus.
B
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All living organisms are dependent upon plants because ____
a. plants produce carbon dioxide as a by-product of photosynthesis b. as producers, they form the base of food chains c. they function to prevent erosion and reduce desertification d. they remove oxygen from the atmosphere e. they contribute to the problems generated by the greenhouse effect
Dr. Askins performs an electrophysiology experiment. She records a neuron at rest. What voltage does she record?
a. -70 mV b. -55 mV c. +35 mV d. +55 mV e. +70 mV
When a sarcomere is at rest, the myosin binding sites on actin are blocked by _____.
A. phosphorous B. sodium C. tropomyosin D. the myosin heads E. AMP
IL-2, produced by TH cells,
A) activates macrophages. B) stimulates TH cell maturation. C) causes phagocytosis. D) activates antigen-presenting cells. E) activates TC cells to CTLs.