You're a famous eye surgeon, specializing in corneal transplants. Give your choice, would you rather have a cornea for transplantation from a 20 year old individual, or a 60 year old individual (assuming there are no optical defects due to age), and why?
A. The 60 year old-clearly, if the individual has gone 60 years with no optical defects, this is a very good organ for transplantation. The 20 year old cornea may have defects that simply haven't become apparent yet.
B. The 20 year old cornea-younger is always better when dealing with tissue transplants. You want to give the transplant the longest possible time for survival in the recipient.
C. The 20 year old cornea-while extremely rare, it may be possible to transmit prions through corneal transplants. It's less likely that a 20 year old would have encountered and become contaminated by prions than the 60 year old.
D. The 20 year old cornea-never mind prions, there are a variety of agents that can hide in corneal tissues and that might cause disease. It's far more likely that the 60 year old would be harboring one or more of these pathogens than the 20 year old.
C.
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A. nucleotides B. amino acids C. phospholipids D. nucleic acid chains E. polypeptides
Species of the genus Thiobacillus
A. oxidize inorganic sulfur compounds and produce ATP. B. are ubiquitous in soil, freshwater, and marine environments. C. produce acids that leach metals out of ore. D. All of the choices are correct.
Which statement concerning root hairs is not correct?
A. Root hairs are tubular extensions of individual epidermal cells. B. A root hair is isolated from its epidermal cell with a cross wall. C. Root hairs generally live only a few days before being sloughed off. D. Root hairs increase the absorption of water and minerals. E. Root hairs are located in the zone of maturation of a root.
The two closely allied organ systems that allow for running, swimming, and flying under the direction of the nervous system are the _____ systems.
A. skeletal and endocrine B. muscular and endocrine C. muscular and skeletal D. circulatory and muscular E. circulatory and skeletal