Pest control methods like pesticides, herbicides, fungicides, rodenticides, and insecticides reduce crop damage and raise yields, but they also create trade-offs. In AP Environmental Science, you should connect repeated chemical use to resistance through artificial selection, harm to non-target species, and the genetic-diversity risks of relying on engineered pest-resistant crops.
Why This Matters for the AP Environmental Science Exam
Pest control is one of the agricultural practices in Unit 5, which carries a noticeable share of the exam. This topic fits the unit's main thinking pattern: describe a human practice, then explain its benefits and drawbacks. You should be able to connect pesticide use to resistance through artificial selection and tie genetically engineered crops to a loss of genetic diversity. These cause-and-effect chains show up in multiple-choice questions and in free-response questions that ask you to describe a practice, explain a consequence, or propose and evaluate a solution.
Key Takeaways
- Pesticides, herbicides, fungicides, rodenticides, and insecticides reduce crop damage by pests and increase crop yields.
- Repeated use leads to resistance through artificial selection: survivors pass on resistance, so the pest population becomes harder to control.
- These chemicals can harm non-target species, including pollinators and aquatic life, and can move through soil and runoff.
- Genetically engineered crops can resist pests and diseases.
- A drawback of relying on genetically engineered crops is reduced genetic diversity within that crop.
- For free-response answers, always pair a benefit with a drawback when a question asks you to evaluate a method.
Pesticides and Their Types
A pesticide is any substance used to control pests, which can include unwanted plants and animals. The exam names several common types you should recognize.
Herbicides
Herbicides target unwanted vegetation like weeds or grasses. They can be selective, affecting only certain plants, or non-selective, affecting most plants they contact. Glyphosate-based products are a common real-world example of an herbicide, and herbicide-resistant weeds are an application of resistance evolving through artificial selection.
Fungicides
Fungicides control fungal infections on plants, seeds, or soil. They work by disrupting fungal growth or reproduction, or by blocking fungi from colonizing the treated plant.
Rodenticides
Rodenticides are designed to control rodents such as mice and rats. They are used in agriculture to protect crops and in urban areas to manage rodent populations. Like other pesticides, repeated use can select for resistant individuals over time.
Insecticides
Insecticides target insects. Many work broadly and can harm helpful insects along with pests. Insecticide exposure is one factor linked to declines in pollinator populations, which is an example of how non-target species are affected.
Pesticides: Benefits and Drawbacks
| Benefits | Drawbacks |
|---|---|
| Reduce crop damage from pests, which increases crop yields and supports a steady food supply. | Can be toxic to non-target species such as birds, bees, mammals, and aquatic organisms. |
| Can reduce spread of pest-carried diseases by controlling the organisms that transmit them. | Can contaminate soil and water through runoff and leaching. |
| Can be used against invasive or parasitic species to protect needed crops and species. | Pests develop resistance through artificial selection, which drives up the amount and cost of pesticide needed. |
Think carefully about both sides whenever a question asks you to evaluate pesticide use. The exam rewards balanced reasoning, not just listing one side.
Genetically Engineered Crops
Crops can be genetically engineered to resist pests and diseases, which can reduce the need for chemical pesticides. The trade-off is that planting large amounts of one engineered crop can lower the genetic diversity of that crop. Low genetic diversity makes a crop more vulnerable if a new pest or disease appears, since fewer plants carry traits that could survive it.
How to Use This on the AP Environmental Science Exam
Free Response
When a prompt asks you to evaluate a pest control method, name the method, then give a specific benefit and a specific drawback. For pesticides, a strong pairing is "increases crop yields by reducing pest damage" as the benefit and "pests evolve resistance through artificial selection" or "harms non-target species through runoff" as the drawback.
Cause and Effect
Be ready to explain resistance as a process: a pesticide affects most pests, but a few survive because they happen to carry resistance, those survivors reproduce, and the next generation has more resistant individuals. That is artificial selection, not pests "learning" to resist.
Common Trap
If a question asks for a drawback of genetically engineered crops, connect it to loss of genetic diversity rather than vaguely saying they are "unnatural" or "unsafe." Tie the loss of diversity to greater vulnerability when a new threat appears.
Common Misconceptions
- Pests do not develop resistance because they were exposed and "got used to" the chemical. Resistance spreads because resistant individuals already exist, survive, and reproduce. That is artificial selection.
- Pesticides are not perfectly targeted. Many affect non-target species, including helpful insects, birds, and aquatic life.
- Genetically engineered crops are not free of drawbacks. Even though they can reduce pesticide use, relying on them can reduce a crop's genetic diversity.
- "Pesticide" is a broad term. Herbicides, fungicides, rodenticides, and insecticides are all pesticides aimed at different kinds of pests.
- More pesticide does not always mean better control. As resistance builds, farmers may need more chemical to get the same effect, which raises cost and environmental harm.
Related AP Environmental Science Guides
Vocabulary
The following words are mentioned explicitly in the College Board Course and Exam Description for this topic.Term | Definition |
|---|---|
artificial selection | The process by which organisms with traits that help them survive a particular pressure (such as pesticide exposure) are more likely to reproduce, passing those traits to offspring. |
crop yields | The amount of agricultural product harvested from a given area of land. |
fungicides | Chemical substances used to kill or prevent fungal diseases on plants. |
genetic diversity | The variation in genes within a population, which enables the population to respond to environmental stressors. |
genetically modified organisms (GMOs) | Organisms whose genetic material has been altered to enhance desired traits, such as crop yield or pest resistance. |
herbicides | Chemical substances used to kill or control unwanted plants (weeds). |
insecticides | Chemical substances used to kill or control insects. |
pest control | Methods and strategies used to manage, reduce, or eliminate pest populations that damage crops or other resources. |
pesticides | Chemical substances used to reduce or control pests, which can pose risks to wildlife, water supplies, and human health. |
resistance | The ability of organisms to survive exposure to a pest control method, typically developed through repeated exposure and artificial selection. |
rodenticides | Chemical substances used to kill rodents such as rats and mice. |
Frequently Asked Questions
What are pest control methods in AP Environmental Science?
Pest control methods are ways to reduce crop damage from unwanted organisms. APES focuses on pesticides, herbicides, fungicides, rodenticides, insecticides, and genetically engineered crops, plus the benefits and drawbacks of each.
What is an insecticide in APES?
An insecticide is a type of pesticide used to control insect pests. It can increase crop yields, but it can also affect non-target insects such as pollinators.
How do pesticides increase crop yields?
Pesticides reduce crop damage by limiting pest pressure. With fewer pests consuming or damaging crops, farmers can harvest more usable food from the same land.
How does pesticide resistance happen?
Pesticide resistance happens through artificial selection. Individuals with resistance survive exposure, reproduce, and pass resistance traits to offspring, making the population harder to control over time.
What is a drawback of genetically engineered crops?
Genetically engineered crops can resist pests and diseases, but relying heavily on one engineered crop can reduce genetic diversity and make that crop more vulnerable to future pests or diseases.
How is pest control tested on the APES exam?
APES questions often ask you to describe a pest control method, explain one benefit and one drawback, connect pesticide resistance to artificial selection, or evaluate genetically engineered crops.