Chapter 43 described an important experiment by Otto Loewi that demonstrated the existence of chemical neurotransmitters. Loewi used frog hearts in dishes that exhibited a regular heartbeat even when disconnected from the rest of the body. This experiment would not have been possible if these hearts lacked
A. sinoatrial nodes.
B. atrioventricular nodes.
C. neurogenic pacemakers.
D. cardiogenic pacemakers.
E. atrioventricular valves.
A. sinoatrial nodes.
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The nitrogenous base that is only found in RNA and not DNA is:
A. adenine B. cytosine C. uracil D. guanine E. thymine
How do fungi digest their food sources? Select all correct choices
A. by engulfing food particles and digesting them in vacuoles B. by extending hyphae into a food source (e.g., an animal carcass) C. by secreting enzymes externally, directly into their surrounding environment D. by funneling food particles through septa, which break down larger molecules
Which of the following features would have helped early plant ancestors evolve to a terrestrial existence?
A. apical cells B. plasmodesmata C. a cuticle D. placenta E. All of these features would have helped.
The features of the strain Salmonella typhimurium include the following EXCEPT:
A. It is a yeast strain. B. It is histidine auxotroph. C. It cannot grow without histidine supplements D. It can mutate to become a revertant that can grow without histidine supplements.