An example of a typical pioneer species, that is one that appears in the earliest stages of ecological succession, is

a. weeds.
b. spider.
c. oak tree.
d. humans.

Humans I think because they are big pioneers

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

Because people are wasting it