4.5: Problems with Pesticides pg. 142
Key Concepts:
1. Pesticides are used to reduce crop losses due to insects, weeds, and other pests.
2. Pesticides have ecological costs.
Pollution
When pesticides are applied, some is carried away by wind to other areas causing sair, soil, or water pollution. Ground water can be contaminated, affecting drinking water for humans and damaging food webs.
Non-target Organisms
The target organisms are not the only organism that may be affected by pesticides. Bees used for pollinating may be killed by insecticides even if they are not the target organism.
Bioaccumulation
Bioaccumulation: is the concentration f a substance, such as a pesticide, in the body of an organism.

Pesticide can accumulate inside organisms. This occurs because the organism cannot break them down chemically or remove as waste. The chemical build up in concentration within the organism’s tissue or organs. Most of these chemical are not water soluble, but dissolves into the fats or oils of an organism.
Birds, bald eagles, and peregrine falcons have declined in numbers because of the pesticide DDT that has accumulated in their bodies. DDT affects the egg shells strength. DDT was banned in 1985.
Bioamplification
Bioamplification: is the increase in concentration of a substance, such as a pesticide, as it moves higher up the food chain or food web.
This occurs when the pesticide becomes more concentrated and moves up the food chain to other levels. When an organism eats another organism which has bioaccumulation they the pesticide concentration is passed on to the consumer.
Resistance to Pesticides
Over long periods of pesticide use, organisms can become resistant to them.
The resistance can be passed on from one generation to another.

Figure 2: Resistance to Pesticides
Check Your Learning:
Questions 1 – 7, pg. 143
Wrap Up:
- Although pesticide use has its benefits, it can also cause harm.
- Pesticides can pollute the air, water, and soil.
- Pesticides can harm species that are not the intended target.
- Pesticides can build up in the bodies of individual organisms and be passed along the food chain.