Which of the following statements about the protonephridia of freshwater flatworms is correct?
A. Fluid from the body enters the
protonephridia without first being filtered.
B. Protonephridia are surrounded by a
capillary network to allow for selective
reabsorption and secretion.
C. The urine leaving the body of a freshwater
flatworm is more concentrated than its body
fluids.
D. Muscular contractions drive fluid
movement through the excretory tubules.
E. The fluid passing through the tubules is not
modified prior to excretion.
A
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Two structures that allow bacteria to adhere to surfaces are ________ and ________.
A. endospores; metachromatic granules B. fimbriae; capsules C. pili; ribosomes D. lipopolysaccharide; techoic acid E. actin filaments; phospholipid membranes
Despite advances in microscopy during the late 1800s and early 1900s, experiments using bacteria as test subjects required careful precautions to prevent contamination that would have invalidated results. What advantage did bacteria have over other, larger organisms that could be used as test subjects, such as mice and pea plants?
a. Larger organisms used as test subjects are more susceptible to injury and disease. b. Bacteria do not require specialized equipment to be stored and transported like other test subjects. c. Bacteria reproduce rapidly, allowing experiments to be conducted and repeated more often. d. Unlike mice and pea plants, bacteria can be frozen for display without cellular damage.
What is one possible advantage to targeting quorum-sensing mechanisms for antibiotic development?
A) There may be no selective advantage to individual cells that are resistant to quorum-sensing inhibitors. B) There is a selective advantage to those cells lacking a quorum-sensing system. C) Quorum-sensing mechanisms are found in all pathogenic bacteria. D) Quorum-sensing mechanisms are found only in human pathogens.
Which list represents the hierarchy of muscle structure from the largest unit to the smallest?
a. muscle fiber ? myofibril ? sarcomere ? filaments b. myofibril ? muscle fiber ? sarcomere ? filaments c. sarcomere ? myofibril ? filaments ? muscle fiber d. muscle fiber ? sarcomere ? myofibril ? filaments e. muscle fiber ? filaments ? myofibril ? sarcomere