In cells with a normally functioning CFTR molecule, this molecule moves chloride ions (with
a negative charge) out of the cell to the covering mucus on the outside. Positively charged
sodium ions then follow these chloride ions out of the cell to maintain electrical balance. This
increases the total electrolyte concentration in the mucus, resulting in the movement of water
out of the cell, and this water helps provide a fluid environment. People that have a defective
gene (and thus a nonfunctioning CFTR molecule) produce abnormally thick and sticky mucus
that builds up in the ducts and passageways. The buildup of this sticky mucus results in lifethreatening
lung infections and serious digestive problems.
Many charged particles such as ions cannot pass directly across the plasma membrane.
Thus, passive transport of the chloride and sodium ions occurs via what process?
a. facilitated diffusion
b. active transport
c. bulk transport
d. osmosis
A
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The first step in the Gram-stain sequence is the application of _______, which is the primary stain
a. safranin b. crystal violet c. Gram's iodine d. Gram's decolorizer
Some animals have evolved sexual maturity in juvenile body forms. This is called ____
a. allometric growth b. vicariance c. paedomorphosis d. punctuated equilibrium e. convergence
Among explanations for tropical diversity, why does the discussion focus heavily on factors that might be responsible for diversity in tropical plant communities?
A) Most tropical biologists study plants, not animals. B) Animals play insignificant roles in tropical ecosystems. C) The diversity of animals is linked closely to the diversity of plants, so an understanding of plant diversity helps us to understand the diversity of animals as well. D) Flowering plants dominate most tropical ecosystems, and flowering plants have been on earth much longer than animals.
A microscope that exposes specimens to ultraviolet, violet, or blue light and forms an image with the light emitted at a different wavelength is called a ________ microscope.
A. fluorescence B. scanning electron C. dark-field D. phase-contrast