---
title: "Pesticide — AP Environmental Science Definition & Exam Guide"
description: "A pesticide is a chemical used to kill crop pests. Learn how it drives genetic resistance, why it shows up in Unit 5, and how the AP exam tests its trade-offs."
canonical: "https://fiveable.me/ap-enviro/key-terms/pesticide"
type: "key-term"
subject: "AP Environmental Science"
---

# Pesticide — AP Environmental Science Definition & Exam Guide

## Definition

In AP Environmental Science, a pesticide is a chemical used to kill or control organisms that damage crops, such as insects, weeds, and fungi. It boosts crop yield but can drive pest resistance through artificial selection and harm non-target species (Topic 5.6).

## What It Is

A **pesticide** is a [chemical](/ap-enviro/unit-8/lethal-dose-50-percent-ld50/study-guide/TAa4nnWGzeffK0Gvo6iO "fv-autolink") you spray to kill pests that eat or compete with crops. "Pesticide" is the umbrella word, and the specific types just tell you the target: **herbicides** kill weeds, **fungicides** kill fungi, **rodenticides** kill rodents, and **insecticides** kill insects. They all fall under Topic 5.6 (Pest Control Methods).

The payoff is real. Pesticides cut crop damage and push yields up, which is why farmers use them. But there's a catch the AP exam loves. Spray a field and you kill most of the pests, but the few that happen to survive carry a gene for resistance. They breed, and the next generation is harder to kill. That's **[artificial selection](/ap-enviro/key-terms/artificial-selection "fv-autolink")** doing exactly what natural selection does, except you're the selective pressure (EK EIN-2.G.1). Over time you get pesticide-resistant [populations](/ap-enviro/unit-3 "fv-autolink") and a chemical that no longer works. On top of that, pesticides drift to non-target species and can wash into groundwater, so they're also one of the agricultural practices that cause environmental damage (Topic 5.4).

## Why It Matters

Pesticides live in **[Unit 5](/ap-enviro/unit-5 "fv-autolink"): Land and Water Use**, anchoring two topics at once. Topic 5.6 asks you to describe the benefits and drawbacks of pest control methods (learning objective 5.6.A), and pesticides are the headline example of that trade-off: higher yields versus resistance and ecosystem harm. Topic 5.4 (objective 5.4.A) treats pesticide application as an agricultural practice that damages the environment, alongside [tilling](/ap-enviro/key-terms/tilling "fv-autolink"), fertilizers, and slash-and-burn. The big idea here is **EIN (Energy and Information)**: human choices to maximize food production trigger biological and chemical consequences that ripple outward. If you can explain why spraying a chemical eventually makes it useless, you've nailed the core skill this unit tests.

## Connections

### [Artificial Selection (Unit 5)](/ap-enviro/key-terms/artificial-selection)

Pesticide [resistance](/ap-enviro/unit-5/pest-control-methods/study-guide/dXLmUIL3KlkvJHKqr02Z "fv-autolink") IS artificial selection in fast-forward. By killing every pest except the naturally resistant ones, you hand the survivors the whole field to breed in, so the resistant trait spreads fast.

### Integrated Pest Management (IPM) (Unit 5)

IPM is the answer to the pesticide problem. Instead of relying on one chemical, you mix biological controls, [crop rotation](/ap-enviro/key-terms/crop-rotation "fv-autolink"), and targeted spraying so pests never get a clean shot at evolving resistance.

### [Genetically Engineered Crops (Unit 5)](/ap-enviro/key-terms/genetically-engineered-crops)

GE crops are an alternative to spraying. You build pest resistance into the plant's genes instead of applying it from a can, though the trade-off is a loss of crop [genetic diversity](/ap-enviro/key-terms/genetic-diversity "fv-autolink") (EK EIN-2.G.2).

### Fertilizers and Monocropping (Unit 5)

Pesticides rarely act alone. Combine heavy spraying with synthetic fertilizers and fields of identical plants, and you get the classic recipe for groundwater contamination and vulnerable, uniform crops.

## On the AP Exam

Pesticides show up in both multiple-choice and FRQs. MCQ stems ask you to pin down cause and effect, like which practice most directly creates pesticide-resistant insects (answer: repeated use of the same pesticide) or which method triggers secondary pest outbreaks. FRQs go further. The 2021 FRQ Q2 framed it directly: pesticides increase food production but can harm humans and other organisms, so you have to argue both sides. The 2022 FRQ Q1 tied pesticide pollution to wildlife (snapping turtle nesting sites), and a 2018 SAQ used the term too. On these, you need to DO three things: explain a benefit (higher yield, less crop loss), explain a drawback (resistance, non-target harm, groundwater contamination), and connect resistance back to artificial selection.

## Pesticide vs Herbicide

A herbicide is a TYPE of pesticide, the one that targets weeds. Pesticide is the broad category that also covers insecticides, fungicides, and rodenticides. Don't treat them as separate, opposite things on the exam; herbicide sits inside the pesticide umbrella.

## Key Takeaways

- A pesticide is any chemical used to kill crop pests, and herbicides, fungicides, rodenticides, and insecticides are all specific types of it.
- Pesticides increase crop yield and reduce crop damage, which is their main benefit (EK EIN-2.G.1).
- Repeated pesticide use causes resistance through artificial selection, because the survivors that carry resistance genes breed and dominate the next generation.
- Pesticides harm non-target species and can contaminate groundwater, making them an agricultural practice that damages the environment (Topic 5.4).
- Integrated Pest Management and genetically engineered crops are the main alternatives the AP exam wants you to know for reducing pesticide reliance.

## FAQs

### What is a pesticide in AP Environmental Science?

It's a chemical used to kill or control organisms that damage crops, including insects, weeds, and fungi. On the AP exam it's the central example of pest control's trade-off: higher crop yields versus pest resistance and environmental harm (Topic 5.6).

### Do pesticides stop working over time?

Yes. Because the pests that survive a spraying are the ones with resistance genes, they breed and pass that resistance on, so the population becomes harder to kill with each generation. This is artificial selection, and it's exactly why the AP exam links pesticides to resistance.

### What's the difference between a pesticide and a herbicide?

A herbicide is one type of pesticide, the kind that kills weeds. Pesticide is the broad umbrella that also includes insecticides, fungicides, and rodenticides, so every herbicide is a pesticide but not every pesticide is a herbicide.

### What are the alternatives to pesticides on the AP exam?

The two big ones are Integrated Pest Management (IPM), which combines biological and chemical controls to slow resistance, and genetically engineered crops, which build pest resistance into the plant itself. GE crops carry the drawback of reduced crop genetic diversity (EK EIN-2.G.2).

### How are pesticides tested on the AP Environmental Science FRQ?

FRQs ask you to weigh benefits against drawbacks, like the 2021 FRQ Q2, which stated pesticides can be both beneficial and harmful. You typically need to name a benefit (increased yield), a drawback (resistance, non-target deaths, or groundwater pollution), and explain resistance as artificial selection.

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