What is a Bioassay?

Bioassay   A bioassay involves the use of biological organism to test for chemical toxicity. Canaries are used by coal miners as a way to test for high levels of methane (an odorless gas)

Used by the FDA   Bioassays are used to test drugs and skin care products before being “okayed” by the FDA.

QoD – In Science Notebooks 1. What is a bioassay? Use complete sentences. 2. What do we always wear for safety in the laboratory?

Using Bioassays for Environmental Research5 BIOASSAYS  Dose/Response Bioassays are used to: Estimate toxicity to humans and other organisms. Estimate toxicity to humans and other organisms. Estimate maximum concentrations of specific chemicals allowed to discharge into bodies of water. Estimate maximum concentrations of specific chemicals allowed to discharge into bodies of water. Investigate hazardous waste sites. Investigate hazardous waste sites.

6 Bioassay Species  3 organisms are often used Daphnia Daphnia Duckweed Duckweed Lettuce Seeds Lettuce Seeds  Expose organisms to chemicals and measure how they respond.

Using Bioassays for Environmental Research7 Bioassay Species  Lettuce Seeds In Petri dishes with test samples In Petri dishes with test samples After 5 day check for: After 5 day check for: germination (sprouting) germination (sprouting) radicle length (length of the sprout) radicle length (length of the sprout)

Using Bioassays for Environmental Research8 CONCENTRATION VS. DOSE  LD 50 the Dose that is Lethal for 50% of the test organisms. Used for Daphnia Used for Daphnia  TC 50 the Concentration that causes a 50% drop in growth or health of the test organisms (Toxic Concentration). Used for seeds (they may not die, just not sprout) Used for seeds (they may not die, just not sprout)

Using Bioassays for Environmental Research9 An Introduction To Experimental Design  The Manipulated Variable in an experiment represents the factor that you vary while keeping everything else constant.

10 An Introduction To Experimental Design  The Responding Variable (Dependent Variable) in an experiment represents what we measure (what we expect to vary depending on the manipulated variable). Radicle Length

Using Bioassays for Environmental Research11 An Introduction To Experimental Design  The control is the untreated group, used for comparison with the treatment groups.

Using Bioassays for Environmental Research12 An Introduction To Experimental Design  Replicates (trials) are groups of organisms exposed to identical conditions. The more replicates the better. The more replicates the better.

Safety   Always wear your gloves and glasses   No eating or drinking   No horseplay!