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: Mammals conserve body heat with their hair or fur. 
Fact 2: Hair and feathers are both made of keratin.

SOLUTION: mammals conserve body heat with keratin.

PROBLEM: Fact 1: Urine leaves the body through a sphincter in the process of urination. 
Fact 2: Fluids in the urine eliminate metabolic waste products.

SOLUTION: Metabolic waste products can leave the body through a sphincter.

PROBLEM: Fact 1: Most invertebrates have a nervous system. 
Fact 2: Invertebrates are animals without a backbone.

SOLUTION:
Most animals without backbones have a nervous system.