Hi. I noticed that the graph is not attached in your post. I researched further and found the similar item and the graph. Here is my answer to your question.
The conclusion is that a lizard's body temperature is about the same as the temperature of its environment.
It could be pollution from a wastewater treatment plant , an industrial plant that have entered the pond or elements from septic tanks, stormwater coming in from farms, urban areas and residential homes and even from rainfall, When the climate is warmer , right temperature, and sunlight
Newton’s 2nd law:
f=ma
force = mass x acceleration
A spring surface. hope that helped