Sponges, cnidarians, and flatworms lack a specialized gas exchange surface because
A) they are too large for a circulatory system to operate well.
B) they live without need for oxygen.
C) they do not produce carbon dioxide.
D) countercurrent exchange mechanisms cannot function well in their living conditions.
E) nearly all of their cells are in direct contact with the external environment.
Answer: E) nearly all of their cells are in direct contact with the external environment.
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Fatty acids that contain no carbon-carbon double bonds are referred to as ____
Some help with this, please?
In the reactions of glycolysis, acetyl-CoA formation and the citric acid cycle, chemical energy is transferred to the bonds in:
A. ATP. B. electron carriers. C. fats. D. a and b are correct. E. a, b, and c are all correct.
Extracellular glucose inhibits transcription of the lac operon by _____
A) strengthening the binding of the repressor to the operator B) weakening the binding of the repressor to the operator C) inhibiting RNA polymerase from opening the strands of DNA to initiate transcription D) reducing the levels of intracellular cAMP
If all of the hairlike structures, called ________, in respiratory passages suddenly stopped working, a person would probably have more respiratory infections
Fill in the blank(s) with correct word