Many substances have been shown to accumulate in ecosystems, including the pesticide dichlorodiphenyltrichloroethane (DDT), which was described in the 1960s bestseller, Silent Spring, by Rachel Carson. DDT was a commonly used pesticide before its dangers became known. In some aquatic ecosystems, organisms from each trophic level consumed many organisms of the lower level, which caused DDT to increase in birds (apex consumers) that ate fish. Thus, the birds accumulated sufficient amounts of DDT to cause fragility in their eggshells. This effect increased egg breakage during nesting and was shown to have adverse effects on these bird populations. The use of DDT was banned in the United States in the 1970s. This is an example of which of the following?
a. biomass
b. concentrated bioproductivity
c. biomagnification
d. bioentropy
c. biomagnification
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What is responsible for the high processivity of the Pol III holoenzyme?
A. The dNTP loader complex ensures continuous replication. B. Because it has three polymerase cores, it can replicate three times as much DNA. C. The hand-shaped structure of the polymerase core grasps the template DNA. D. The ? sliding clamp allows Pol III to stay associated with the DNA template as each nucleotide is added. E. The "thumb" structure of the Pol III polymerase core holds the DNA template tightly.
Which of the following best describes the relationship between DNA, proteins, and RNA?
A. DNA is transcribed into RNA, then RNA is translated into proteins. B. DNA is transcribed into proteins, then proteins are translated into RNA. C. DNA is translated into RNA, then RNA is transcribed into proteins. D. DNA is translated into proteins, then proteins are transcribed into RNA.
Dividing adult eukaryotic cells spend most of their time in which of the following?
A) metaphase B) prophase C) telophase D) interphase E) anaphase
Which of the following results from the release of the neurotransmitter dopamine into the nerve synapse?
a) the presynaptic neuron fires an action potential b) Dopamine binds to receptor proteins on the membrane of the postsynaptic cell c)Dopamine enters the cytoplasm of the postsynaptic cell d) dopamine cause the postsynaptic nerve cell to contract