Which of the following are characteristics of attenuated viral vaccines?
a. They provide short-lived immune responses.
b. They are easy to store and maintain their potency for long periods of time.
c. They provide long-lasting T cell–mediated immunity.
d. They do not develop long-term memory responses.
Answer: C
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When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell?
A) There is random movement of substances into and out of the cell. B) There is directed movement of substances into and out of the cell. C) There is no movement of substances into and out of the cell. D) All movement of molecules is directed by active transport.
More _____ need to be studied in order to find out whether interspecific competition strongly influences the species
composition and structure of most communities.
a. communities b. K-selected species c. r-selected species d. predators e. prey species
Meiosis produces
a. sperm cells. b. egg cells. c. body cells. d. sperm and egg cells. e. sperm, egg, and body cells.
Currently the only predators of Galápagos marine iguanas are Galápagos hawks. Iguana body size is not correlated with risk of hawk predation, although small iguanas can sprint faster than large iguanas
If predators (for example, cats) that preferably catch and eat slower iguanas are introduced to the island, iguana body size is likely to _____ in the absence of other factors; the iguanas would then be under _____ selection. A) increase; directional B) increase; disruptive C) decrease; directional D) decrease; disruptive