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11 Cards in this Set
- Front
- Back
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How are antibiotics misused or overused? |
It has become an addiction, and its success has led to complacency. -Antibiotic expectation: 18 million courses of antibiotics are prescribed for the common cold which is a virus, another 50 million for respiratory viruses. 68 mil unnecessary courses per year -Sanitary Obsession: excessive use of antibiotic soap and household cleaner -Farming use: 50% of global antibiotic production is used on farm animals |
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Why is sickle cell trait more common in malarial regions? |
Sickle cells are resistant to Plasmodium invasion. Benefit of this resistance in these regions outweighs the detrimental effects of having sickle cells. |
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How does this demonstrate natural selection? |
In these malarial regions, the heterozygotes have a higher fitness than the homozygotes, and so they have a greater chance of surviving malaria invasions to become of reproductive age and thus are able to pass on their alleles. Over time, sickle cells will become more prevalent in the population as this trait is selected for. |
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Why do doses of drugs and toxins decay? |
-Always concentrated, lands on surfaces and mixes with other particles -Therefore, become diluted over time -Dosage depends on when the organism comes into contact with the toxin (e.g. how long after the spraying did the insect land on the surface) |
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How does decay rate influence the selection for resistance? |
The decay rate is proportional to selection time - increasing decay rate will decrease the selection time. After decaying to a certain point, partial resistants survive, normals do not (selection) Decaying low enough, all survive (No selection) Therefore, % of Partial resistants increases leading to potential selection for fully resistant individuals Resistance will continue to increase while selection pressure remains |
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What is the diagram that illustrates how decay rate influences selection? |
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What is the zone of selection? |
A dosage concentration interval where resistants survive but normals die. |
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What is the selection time? |
The time interval in which resistants survive, but normals die. |
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Why is resistance rare in the absence of selection? |
Mutations that lead to resistance against certain toxins are normally detrimental in the absence of those toxins. New mutations always have bad side effects e.g. less efficient digestion, and therefore are selected against unless the pesticide/drug is present |
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How can selection for resistance be minimised? |
-Repeat regularly to keep dosage high (e.g. complete courses of drugs) -Don't delay until pest returns (e.g. repeat at short intervals) -Use chemicals with rapid decay (e.g. minimises selection time during decay) -Prevent unnecessary use (edge effects) -Prevent dispersion of resistant pests |
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Give an example of an alternative to using pesticides to control vectors or pathogens and explainwhy it should work and whether there are risks. (For example, biological control using a parasite) |
Biological controls (introducing a predator/parasite of the pathogens/pests) encourages a better natural balance e.g. Parasitoid wasps The predator/prey relationship is a self-contained system, general levels of both pathogen and parasite are low compared to the spikes in chemical controls. Risks are involved in this: -Predator needs to be specific -Must not disperse far from the site -Must not become a pest -Must not completely decimate pathogen/pest population |
