1. Who, What, Where, When and Why? Science (scientia : to know)

6. The Scientific Method: A model for problem solving that follows a well defined procedure

8. Defining the Problem What is causing limb mutations in Amphibians?

9. Collecting Information w Amphibian skin is permeable to substances in the water, air and land. w Amphibians start their life in water and end up land; they are exposed to many threats w Increased UV radiation is getting through a thinning ozone layer. w Retinoic acid occurs in vertebrate embryos and influences the development of limbs. w Trematode cysts have been found clustered in developing limb buds.

10. Hypotheses w Increased UV radiation is damaging the genes directing limb development (R. Mc Kinnell) w Chemicals in the water, acting either singly or together, are penetrating the frog’s skin causing mutations. w Abnormally high concentrations of retinoic acid and similar chemicals are affecting limb development at the tadpole stage. (J. Bantle) w Trematode cysts are splitting developing limb buds in multiple places. (S. Sessions)

11. Testing the Hypotheses w Tissue samples are observed under the microscope. Searching for damaged chromosomes. (Mc Kinnell) w Tadpoles are incubated for 72 hours in a solution containing an insecticide that was subjected to UV radiation. (Previous tests indicate that certain insecticides are transformed into retinoid like compounds in the presence of UV radiation. J. Bantle) w Plastic beads are surgically implanted into developing limb buds. The beads mimic trematode cysts. The tadpoles are allowed to develop under normal conditions. (S. Sessions)

12. Conclusions w No visible genetic damage was determined with the technique used by Mc Kinnell. Other techniques will be applied to retest the hypothesis. w Bantle concluded that insecticides can be transformed into chemicals (when subjected to UV radiation) that can cause mutations like those observed. w Sessions showed that plastic beads inserted into developing limb buds can cause mirror image duplications. Actual cysts need to be implanted into developing limb buds and analyzed.