1. What tools do scientists use to test the toxicity of different chemicals?

2. Outline Bioassay background (5 mins)
Activity 1: Sublethal effects of chemicals (15-20 mins)
Activity 2: Lethal effects of chemicals (15-20 mins)
Discussion (5-10 mins)

3. Teaching Standards Environmental science standards Biology standards
Recognize that humans are part of the global ecosystem and evaluate the effects of human activities on ecosystems
Biology standards
Assess how human activities such as pesticide use influence and modify the environment
Relate animal adaptations, including behaviors, to the ability to survive stressful environmental conditions

4. Bioassays What is a bioassay? What is a bioindicator?
What characteristics make a good bioindicator species?
Sensitivity
Representative of the system you are interested in?

5. Bioindicators

6. Daphnia Crustaceans- “water fleas” Filter feeders
Up to 1/4th of an inch in length-easily observable under dissecting microscope
Nearly translucent carapace
Sensitive to environmental changes
heart beat video

7. Acute vs Chronic effect Sublethal effects
Once we choose an indicator species, how do we measure the effects of a chemical?
Acute vs Chronic effect
Sublethal effects
Behavior
Heart rate-stimulants vs. depressants
Lethal effects
LD50
Sublethal effects
Fig 1. Effect of two insecticides on insect survival

8. Dose/concentration is important

9. Activity 1 Record baseline heart rate
Sublethal effects of chemicals on Daphnia magna
Record baseline heart rate
Add a single drop of each solution and measure change in heart rate
Ethanol, sugar solution, hot and cold water

10. Activity 1 Questions Which solutions showed an increase in heart rate?
Which solutions showed a decrease in heart rate?
Which solutions would you classify as stimulants? Depressants?

11. Lethal effects of chemicals on Daphnia magna
Activity 2
Lethal effects of chemicals on Daphnia magna

12. Activity 2 Questions What toxicant did you choose to test? Why?
Which toxicant concentration appeared to have little effect on the Daphnia?
Can you use the results of your bioassay to make predictions about the effect of this toxicant on humans?