Genetic resistance is the evolutionary adaptation of a pest population to a pesticide: the few naturally resistant individuals survive treatment, reproduce, and pass on resistance, so over generations the chemical stops working (CED EK EIN-2.G.1).
Genetic resistance happens when a pest population evolves the ability to survive a chemical that used to kill it. Spray an insecticide, and most of the bugs die. But a few have a random genetic trait that lets them shrug it off. Those survivors are the only ones left to breed, so the next generation has more resistant individuals. Repeat that for a few seasons and the pesticide barely does anything.
This is just natural selection (which the CED calls artificial selection here, since humans are doing the selecting with the chemical). The pesticide is the selection pressure. According to EK EIN-2.G.1, organisms become resistant to pesticides, herbicides, fungicides, rodenticides, and insecticides this way. The flip side, in EK EIN-2.G.2, is that crops can be genetically engineered to RESIST pests, though that can shrink the crop's genetic diversity. Same word, opposite direction: resistance is a problem when pests gain it, a tool when we build it into crops.
This lives in Unit 5: Land and Water Use, topic 5.6 Pest Control Methods, under learning objective AP Enviro 5.6.A (describe the benefits and drawbacks of different pest-control methods). Genetic resistance is the single biggest drawback of chemical pest control, so it shows up every time you weigh pesticides against alternatives. You should be able to explain WHY resistance develops (natural selection on a varied population) and WHY it forces farmers to use more chemical or stronger chemicals over time. That ties directly into the pesticide treadmill and into the human-environment trade-offs the unit is built around.
Keep studying AP® Environmental Science Unit 5
Artificial Selection (Unit 5)
Genetic resistance IS artificial selection in action. Humans don't mean to breed tougher pests, but spraying a chemical kills the susceptible ones and lets the resistant ones reproduce. We're selecting for resistance the same way a breeder selects for traits in dogs.
Pesticide Treadmill (Unit 5)
Resistance is the engine of the treadmill. As a pesticide loses effectiveness, farmers spray more, switch chemicals, or pay for stronger products, which selects for even more resistance. They're stuck running to stay in place.
Genetically Engineered Crops (Unit 5)
Same word, opposite goal. Pests gaining resistance is bad for us, but engineering resistance INTO a crop (like Bt corn) is a tool. The catch from EK EIN-2.G.2 is that monoculture GE crops can lose genetic diversity, and pests can still evolve resistance to the engineered trait.
Crop Yield (Unit 5)
Pest control exists to protect yield. When resistance kicks in, crop damage returns and yields drop, which is exactly why farmers keep escalating their methods. The whole cost-benefit story runs through yield.
Expect MCQ stems that hand you a scenario and ask you to explain renewed pest damage. The classic version: after eight years of planting Bt corn, the European corn borer is damaging crops again. The right answer is that the borer population evolved resistance through natural selection, not that the Bt 'wore off.' Another version asks why a fungicide is 'becoming less effective.' Same logic. On FRQs, the 2021 Q2 set asked about pesticides being both beneficial and harmful, and genetic resistance is the go-to drawback to name and explain. When you answer, don't just say 'they got resistant.' Walk the mechanism: variation exists in the population, the chemical kills susceptible individuals, survivors reproduce, resistance frequency rises.
Both use the word 'resistance,' but they point in opposite directions. Genetic resistance in PESTS is something we cause by accident and want to avoid, because it makes our chemicals useless. Engineered resistance in CROPS is something we deliberately build in to protect the plant. One is the problem, the other is an attempted solution, and a pest can even evolve resistance to the engineered crop.
Genetic resistance is natural selection: a pesticide kills susceptible pests, the few resistant survivors breed, and resistance spreads through the population over generations.
The CED frames this as artificial selection because humans supply the selection pressure (EK EIN-2.G.1).
Resistance is the main drawback of chemical pest control and the driver behind the pesticide treadmill, where farmers must keep escalating their methods.
Genetically engineered crops can be given resistance to pests, but doing so can reduce a crop's genetic diversity (EK EIN-2.G.2).
On the exam, returning pest damage after years of the same pesticide is your signal that the population has evolved resistance, not that the chemical degraded.
It's when a pest population evolves to survive a pesticide through natural selection. The resistant individuals survive treatment and reproduce, so over time the pesticide stops working. It maps to topic 5.6 and EK EIN-2.G.1.
No. The chemical isn't getting weaker. The PEST population is changing. Each spray removes susceptible individuals and leaves resistant ones to breed, so future generations are harder to kill. That's why the same dose works less and less over time.
Pest resistance is something we cause by accident and don't want, because it makes our chemicals useless. Engineered crop resistance is something we deliberately build into a plant (like Bt corn) to protect it. Same word, opposite goals, and pests can even evolve resistance to the engineered crop.
Because the corn borer population evolved resistance to the Bt toxin through natural selection. Borers carrying a random resistance trait survived, reproduced, and became the majority. This is a common AP MCQ scenario, and the right answer is evolved resistance, not a failure of the corn.
Not quite, but they're linked. Genetic resistance is the cause (pests evolve to survive the chemical). The pesticide treadmill is the result (farmers respond by spraying more or switching to stronger chemicals, which selects for even more resistance).
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