When toxic chemicals enter the environment, there is a good chance that they will fid their way into food chains and
food webs. Such was the case with DDT, a chemical that was used to control mosquitoes before it was banned in 1972.
The processes that proved DDT to be so dangerous could be manifested in other substances like heavy metals, other
pesticides and radioactive isotopes. Use the example of DDT to explain why these chemicals can have such far-reaching
effects, making sure you use the terms bioaccumulation, persistence, and biological magnification. What will be an ideal response?
The danger of DDT and similar chemicals is their tendency to increase as they carried
through the food chain. Persistence is a function of the stable chemical structure of a
substance. It means it will remain static in the environment for a log time without breaking
down.
Bioaccumulation is a function of this persistence. Because these chemicals do not break
down, they remain stored in the fatty tissue of the organisms that ingested them. Biological
magnification is the idea that animals higher on the food chain tend to store greater
concentrations of these toxins than animals at lower trophic levels.
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When many genes of an organisms are globally regulated, those genes are considered as regulon genes. What is the common theme of such genetic regulation?
A) Genes of regulons are silenced by a common repressor. B) Genes of regulons are able to transcribe mRNA independent of regulation. C) Genes of regulons are much more stable than non-regulon genes. D) Genes of regulons are much less stable than non-regulon genes. E) Individual genes of regulons are regulated independently of each other.
In which decade of life does the removal of the bone matrix first exceed production of new bone?
A. Second decade B. Third decade C. Fifth decade D. Sixth decade
Intrinsic pacemaker cells are located in the ____
a. Purkinje fibers b. Bundle branches c. AV node d. SA node e. gap junctions
Women who are pregnant or lactating should
A. consume extra calcium. B. increase protein intake. C. consume additional Calories. D. All of the above are correct.