Compare the activation and functions of T and B cells. What will be an ideal response?
ANSWER: B cells respond to antigen exposure by cloning and producing plasma cells and memory cells.
The plasma cells produce antibodies to protect against the antigen; memory cells are able to
respond quickly to subsequent exposure. T cells do not produce antibodies but act directly on
specific target cells. Killer T cells directly destroy infected, cancerous, or transplanted cells
by injecting proteins into the foreign cell’s membrane. These proteins form large pores that
allow salt and water to enter, bursting the cell. Helper T cells release chemicals that help
other immune cells function properly.
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Individuals and conservation groups have donated funds to buy land in the Monteverde Cloud Forest in Costa Rica. As a result, much of the forest is now protected as a private nature reserve. This is an example of:
a. restoration b. preservation c. ecosystem creation d. ecosystem commercialization e. deforestation
Comparing cells synthesizing secretory proteins and cells secreting steroid hormones, the cells synthesizing the steroid hormones have
A) more rough ER. B) more smooth ER. C) equal amounts of smooth and rough ER. D) equal amounts of smooth and rough ER, but more lysosomes. E) equal amounts of smooth and rough ER, but fewer lysosomes.
Which structure is least likely to fossilize?
a. bone b. teeth c. seeds d. shells e. skin
Anabolic steroids:a
are removed from the body fairly quickly due to a low concentration of receptor sites. b. decrease HDL concentration, thereby increasing the risk of cardiovascular disease. c. are naturally produced hormones typically used by athletes for short-term performance enhancement. d. have little or no effect on physiology or behavior at very low doses. e. are metabolized and excreted from the body quickly..