A particular virus consists of only DNA and proteins. Viruses attach to the surface of a host cell and inject the viral DNA into the host. The host cell then copies the viral DNA and makes new viruses
Eventually, the host cell is killed, and the new viruses are released. These new viruses search for new hosts to continue the cycle. Identify and apply at least three characteristics of life to justify whether a virus is a living thing.
Whether a virus is a living thing is debatable. Students may argue that a virus is not alive because it does not reproduce on its own, it is not made of cells, etc. However, a student may argue in the other direction based on his or her interpretation of the characteristics of life. For example, the student might answer that viruses do reproduce by coercing their host cells into copying their contents.
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Which of the following is the greatest threat to biodiversity?
A) overharvesting of commercially important species B) introduced species that compete with native species C) pollution of Earth's air, water, and soil D) disruption of trophic relationships as more and more prey species become extinct E) habitat alteration, fragmentation, and destruction
In muscle contraction, which of the following
triggers the power stroke?
a. release of Pi from the myosin head b. binding of ATP to the myosin head c. hydrolysis of ATP into ADP and Pi d. cross-bridge formation between actin and myosin e. relaxation of the sarcomere
Gastrulation produces
a. hollow balls of cells. b. embryos with primary tissue layers. c. solid balls of cells. d. maternal messages. e. all of these
In feedback inhibition of a metabolic pathway, where does the inhibitor bind?
A. to a substrate or the product of the last reaction B. to the enzyme of the first reaction C. to the enzyme of the last reaction D. to the substrate of the first reaction E. to the product of the first reaction