Define positive feedback and describe why they are not necessarily beneficial to organisms. Include a

description of the changes associated with severe blood loss and circulatory shock to substantiate your
answer. What will be an ideal response?


Concepts to Consider: Positive feedback systems are rare, but when they occur the response to the
stressor leads to a further deviation from the steady state or set point. That is, the response intensifies
rather than reverses the initial change and therefore they do not maintain homeostasis. Hemorrhage is
an example of a stressor that can result in a significant loss of blood. The loss of blood causes a drop in
blood pressure, and less blood will circulate back to the heart. Heart function declines along with a
decrease in cardiac output (volume of blood per contraction of the heart). The overall result is
therefore a further drop in blood pressure associated with this decrease in heart output.

Biology & Microbiology

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The C-terminus of a polypeptide always contains

A. a stop codon. B. a carboxyl group C. an amino group. D. carbon dioxide. E. None of the answers are correct.

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What is the main energy source used by the cells?

a. Starch b. Glucose c. Amino acids d. Fatty acids e. Glycogen

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The organism in the above photograph has which of

the following structural systems? a. cartilaginous b. bone c. hydrostatic d. chitinous e. endoskeletal

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During the Krebs cycle, acetyl CoA covalently binds to oxaloacetate to form citrate, a ________ -carbon molecule

A) five B) three C) six D) four E) two

Biology & Microbiology