AP Environmental Science 8.12 LD₅₀

Practise LD₅₀ questions by comparing toxicity data, identifying safer substances and calculating pesticide doses from concentration and body mass.

Exam points

identify the governing concept or relationship in the problem
justify the result with equations, diagrams or contextual evidence

Covered syllabus points

EIN-3.A—Define lethal dose 50% (LD₅₀)

[Maximum number: 1]

Questions 19-20 refer to the information below. In the 1960s and 1970s the Texas horned toads and lizards were found all over Central and North Texas. However, in 1977 the Texas horned lizard was put on the threatened species list because of many reasons, one being the invasion of the invasive species, the fire ant. The fire ant pushed out the harvester ants (big red ant), which was the majority of the horny toad's/lizard's diet. In addition, farmers began to use pesticide to get rid of the fire ants, an action that also killed the red ants.

In toxicology, many pesticides, like those used to control the fire ant, are tested according to the $\mathrm{LD}_{50}$ levels. $\mathrm{LD}_{50}$ levels are best described by which of the following?

The level that kills 50 pests in 50 minutes

The level that kills 50 pests out of 500

The level that kills the pests but leaves 50 percent of the predators alive

The level that kills 50 percent of the pest population of a particular species

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Covered syllabus points

8.12 Lethal Dose 50% (LD₅₀) question 1