What is the route of water in the water vascular system of a starfish?
A. Water enters through the madreporite into the ring canal and from thence into the radial canals to the ampullae and finally into the tube feet.
B. Water enters the madreporite into the radial canals and from thence into the ring canal, then the ampullae and finally into the tube feet.
C. Water enters the madreporite into the ampullae and from thence into the ring canal, then the radial canals to the ampullae and finally into the tube feet.
D. Water enters the ampullae and then goes to the tube feet and from thence to the radial canals, then the ring canal, and finally exits through the madreporite.
E. Water enters the ring canal, then goes into the radial canals, and finally through the madreporite to the ampullae and tube feet.
A. Water enters through the madreporite into the ring canal and from thence into the radial canals to the ampullae and finally into the tube feet.
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Evidence that cytoskeletal elements have ancient origins comes from:
A. the sequence similarities of cytoskeletal elements when comparing distantly-related organisms. B. the presence of cytoskeletal elements in both eukaryotes and prokaryotes. C. the observation that both prokaryotes and eukaryotes use cytoskeletal elements to assist cell division. D. the ability to form functional hybrid microfilaments from actin monomers taken from distantly-related organisms. E. All of these choices are correct.
Inhibitory postsynaptic potential (IPSP) is associated with membrane depolarization, whereas excitatory postsynaptic potential (EPSP) is associated with hyperpolarization
A. true B. false
People who cannot become infected with HIV have
A) extra T cells. B) deletions in the genes encoding the CCR5 coreceptors. C) a gene encoding a protein that attacks the virus. D) anti-HIV antigens.
Asexual reproduction in ascomycetes takes place by means of
A. ascogonia. B. zygospores. C. motile gametes. D. conidia. E. ascospores.