Many of the signaling pathways used for communication between cells in complex multicellular organisms first evolved in:
A. unicellular eukaryotes.
B. simple multicellular eukaryotes.
C. unicellular prokaryotes.
D. simple multicellular prokaryotes.
E. complex multicellular prokaryotes.
A
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The structure(s) critical to the function of a chemical synapse include
_____ gap junctions. _____ neurotransmitters. _____ vesicles. _____ voltage-gated Ca2+ channels. _____ electrical signals.
Both marine fish and marine mammals have body fluids with a lower salt concentration. However, unlike fish, marine mammals do not drink seawater, although they do swallow some with their food. How are marine mammals able to maintain their internal supply of water?
What will be an ideal response?
Which of the following is true of water-saturated soils?
A. They contain anaerobes. B. They provide gases for soil microbes. C. They have a low carbon dioxide content. D. They have a high oxygen content.
The following is a list of events involved in the activation of a cell by a steroid hormone. Which one of the following answers best represents the order in which the steps occur?
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