Encyclopedia of Evolution.pdf - Online Reading Center

0 respiration, evolution of
There is some concern that the genetic basis of herbicide
resistance, which has been put into crops by genetic engineering,
could spread to wild weed species by crossbreeding (see
hybridization). While this has not happened extensively, it
has occurred: Herbicide resistance has been transferred from
crops to weeds within the crucifer (mustard) family by crosspollination.
Once the resistance genes are in the wild weed
populations, natural selection will favor their spread whenever
herbicides are used.
An evolutionary understanding of medicine, public
health, and agriculture demands that antibiotics, pesticides,
and herbicides be used sparingly in order to minimize environmental
contamination and to prevent the evolution of
resistance in the very species of organisms humans are trying
to control. By restraining the use of chemical control agents,
they will remain effective when they are really needed in an
emergency.
The dangerous emergence of bacteria, pests, and weeds
that resist the chemicals that we use to control them has
resulted from our overuse of chemical control agents. The
overuse of antibiotics, pesticides, and herbicides resulted
not only from overlooking the laws of ecology but also
the laws of evolution. As noted in the Introduction to this
encyclopedia, “what you don’t know about evolution can
kill you.”
Further Reading
Amábile-Cuevas, Carlos F. “New antibiotics and new resistance.”
American Scientist 91 (2003): 138–149.
Brookfield, J. F. Y. “The resistance movement.” Nature 350 (1991):
107–108.
Carson, Rachel. Silent Spring. New York: Houghton Mifflin, 1962.
Department of Health and Human Services, Washington, D.C. “Centers
for Disease Control and Prevention.” Available online. URL:
http://www.cdc.gov. Accessed May 4, 2005.
Enright, Mark C. “The evolutionary history of methicillin-resistant
Staphylococcus aureus (MRSA). Proceedings of the National
Academy of Sciences 99 (2002): 7,687–7,692.
Hegde, Subray S., et al. “A fluoroquinolone resistance protein from
Mycobacterium tuberculosis that mimics DNA.” Science 308
(2005): 1,480–1,483. Summarized by Ferber, Dan. “Protein that
mimics DNA helps tuberculosis bacteria resist antibiotics.” Science
308 (2005): 1,393.
Levy, Stuart B. “The challenge of antibiotic resistance.” Scientific
American, March 1998, 32–39.
Monnet, Dominique L., et al. “Antimicrobial drug use and methicillin-resistant
Staphylococcus aureus, Aberdeen, 1996–2000.”
Emerging Infectious Diseases 10 (2004): 1,432–1,441. Available
online. URL: http://www.cdc.gov/ncidod/eid/vol10no8/02-0694.
htm. Accessed May 4, 2005.
Regoes, Roland R., and Sebastian Bonhoeffer. “Emergence of drugresistant
influenza virus: Population dynamical considerations.”
Science 312 (2006): 389–391.
Smith, P., et al. “A new aspect of warfarin resistance in wild rats:
Benefits in the absence of poison.” Functional Ecology 7 (1993):
190–194.
Stix, Gary. “An antibiotic resistance fighter.” Scientific American,
April 2006, 80–83.
Tiemersma, Edine W., et al. “Methicillin-resistant Staphylococcus
aureus in Europe, 1999–2002. Emerging Infectious Diseases 10
(2004): 1,627–1,634. Available online. URL: http://www.cdc.gov/
ncidod/EID/vol10no9/04-0069.htm. Accessed May 4, 2005.
WeedScience.org. “International Survey of Herbicide Resistant
Weeds.” Available online. URL: http://www.weedscience.org/
in.asp. Accessed May 4, 2005.
Wenzel, Richard P., and Michael B. Edmond. “The impact of hospital-acquired
bloodstream infections.” Emerging Infectious Diseases
7 (2001): 174–177. Available online. URL: http://www.cdc.
gov/ncidod/eid/vol7no2/wenzel.htm. Accessed October 7, 2005.
respiration, evolution of Respiration is the process by
which cells transfer energy from food molecules to ATP.
ATP (adenosine triphosphate) is almost universally used as
the molecule that puts energy directly into enzyme reactions.
And since almost all biological reactions are controlled by
enzymes, ATP is called the “energy currency of the cell.” Cellular
respiration, which produces ATP, occurs in many bacteria
(see bacteria, evolution of), and in the cytoplasm
and mitochondria of eukaryotic cells (see eukaryotes, evolution
of). Food molecules store energy over relatively long
time periods, while ATP puts energy to immediate use. Therefore
mitochondria are like power plants, which transfer the
energy from long-term storage (coal, natural gas) into immediately
available forms like electricity.
The earliest bacteria, during the Archaean eon (see Precambrian
time), were anaerobic: not only was there no oxygen
gas in the environment, but oxygen gas would have been
deadly to them. Their descendants are the anaerobic bacteria
that today can only live in mud and in the intestines of animals.
These bacteria, as well as a few anaerobic protists and
invertebrates (see invertebrates, evolution of), use a set of
reactions called glycolysis to break down glucose sugar molecules
and release some energy from them into ATP. In these
organisms, glycolysis is followed by fermentation. In some
cases, as with yeasts, fermentation produces ethyl alcohol (ethanol);
in other cases, as with Lactobacillus bacteria that make
milk into yogurt, fermentation produces lactic acid (lactate). In
some cases, the cells of organisms that rely upon oxygen can
revert temporarily to a dependence on glycolysis and fermentation,
when oxygen is not available. Muscle cells, for example,
can revert to fermentation when they work so fast that the
blood cannot supply sufficient oxygen to them. Muscle pain
results from the buildup of lactate, and the muscles develop
an oxygen debt. The muscles stop working after a few minutes
of emergency oxygen debt. Ethanol and lactate, however, still
contain most of the energy that was in the original glucose.
During the Proterozoic era of the Precambrian, cyanobacteria
began producing oxygen gas, which gradually accumulated
to become abundant in the oceans and atmosphere
(see photosynthesis, evolution of). This was a crisis for
anaerobic bacteria, which could survive only in the places
where they are found today. However, at this time, some
bacteria evolved a set of reactions (aerobic respiration) that
not only tolerated oxygen gas but actually made use of it.
A cycle of chemical reactions (the Krebs cycle or citric acid
cycle) breaks down the product of glycolysis into carbon