To conduct their experiment, the researchers collected L. peronii eggs from a natural stream.  After the eggs had hatched, tadpoles were raised in artificially constructed 2 L containers in a laboratory.  All containers were filled with 1 L of filtered tap water, and the water was changed every other day.  Thirteen tadpoles were placed in each container, and the tadpoles were exposed to a 12-hour light: 12-hour dark photoperiod.  All tadpoles were fed thawed spinach daily.  The researchers randomly placed the tadpoles into containers exposed to one of four treatments, with nine replicates of each treatment, as follows: Low UVBR (<6.0 kJ/m2), low temperature (15OC) Low UVBR (<6.0 kJ/m2), high temperature (26OC) High UVBR (>70.0 kJ/m2), low temperature (15OC) High UVBR (>70.0 kJ/m2), high temperature (26OC) The researchers recorded the number of tadpoles still alive out of the original 13 in a container (percent survival) at different time periods.  Their results at

To conduct their experiment, the researchers collected L. peronii eggs from a natural stream.  After the eggs had hatched, tadpoles were raised in artificially constructed 2 L containers in a laboratory.  All containers were filled with 1 L of filtered tap water, and the water was changed every other day.  Thirteen tadpoles were placed in each container, and the tadpoles were exposed to a 12-hour light: 12-hour dark photoperiod.  All tadpoles were fed thawed spinach daily. 

The researchers randomly placed the tadpoles into containers exposed to one of four treatments, with nine replicates of each treatment, as follows:

1. Low UVBR (<6.0 kJ/m²), low temperature (15^OC)
2. Low UVBR (<6.0 kJ/m²), high temperature (26^OC)
3. High UVBR (>70.0 kJ/m²), low temperature (15^OC)
4. High UVBR (>70.0 kJ/m²), high temperature (26^OC)

The researchers recorded the number of tadpoles still alive out of the original 13 in a container (percent survival) at different time periods.  Their results at Week 4, showing the averages for each treatment, are shown below.

Figure 1.  Graph of results for effects of temperature and UVB radiation on tadpole survival

Questions

1. Identify all independent variables in the experiment (include units).
2. Identify all dependent variables in the experiment (include units).
3. Describe three standardized conditions in the experiment.
4. Interpret the data in the graph shown in Figure 1. Be sure to address all of the treatments, if a treatment had an obvious effect or not, and what kind of effect it was.