TASK DEFINITION: Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.
PROBLEM: Fact 1: All life relies on a relatively narrow range of pH, or acidity. 
Fact 2: Biochemical reactions are catalyzed by enzymes that have very narrow ranges of optimum pH values.

SOLUTION: All life relies on a relatively narrow range of environment partly do to need of Biochemical reactions being catalyzed by enzymes.

PROBLEM: Fact 1: Introns are regions that do not code for proteins. 
Fact 2: Introns are found in eukaryotes.

SOLUTION: eukaryotes have regions that do not code for proteins.

PROBLEM: Fact 1: an animal usually requires a warm body temperature for survival. 
Fact 2: Mammals are warm blooded animals.

SOLUTION:
Mammals require warm body temperature for survival.