True or false: even single celled organisms have a circulatory system similar to humans.

False

A single-celled organism doesn't need a circulatory system as human do. Since they are singular, they can interact with their environment directly. Unlike them, a multicellular organism like a human has a part where their cells can't get oxygen or food directly, thus need to be supplied by the circulatory system. Some of the cells also well differentiated so it only accept a certain processed food. 

Where is the picture at

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature