How can so many antibody molecules be made in a relatively short period of time? What will be an ideal response?
ANSWER: When an antigen binds to a TCR or an antibody on the surface of a T cell or B cell, it
stimulates that cell to divide, producing a large population of genetically identical
descendants, or clones, all with the same TCR or antibody. This process is called clonal
selection.
The activated B cell divides to form two types of daughter cells. The first type is plasma
cells, which synthesize and secrete 2,000 to 20,000 antibody molecules per second into the
bloodstream. Plasma cells have cytoplasm filled with rough endoplasmic reticulum—an
organelle associated with protein synthesis.
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Which class of antibody is found in body secretions such as tears, saliva, and breast milk?
a. IgA b. IgB c. IgM d. IgG e. IgE
List five mechanisms by which gene frequencies in a population can be altered. Describe each briefly
What will be an ideal response?
Which of these events seem(s) to have occurred among the fly populations on the island?
1. cladogenesis 2. adaptive radiation 3. sympatric speciation A) 1 only B) 2 only C) 3 only D) 1 and 2 only E) 1, 2, and 3
Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?
A) They have been geographically isolated from each other for a longer time. B) Cold temperatures, associated with deep water, have accelerated the mutation rate, resulting in faster divergence in deepwater shrimp. C) The rise of the land bridge was accompanied by much volcanic activity. Volcanic ash contains heavy metals, which are known mutagens. Ash fall caused high levels of heavy metals in the ocean sediments underlying the deep water, resulting in accelerated mutation rates and faster divergence in deepwater shrimp. D) Fresh water entering the ocean from the canal is both less dense and cloudier than seawater. The cloudy fresh water interferes with the ability of shallow-water shrimp to locate mating partners, which reduces the frequency of mating, thereby slowing the introduction of genetic variation.