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.

Fact 1: Some viruses have an envelope of phospholipids and proteins. 
Fact 2: Viruses are enveloped by similar membranes.
viruses have similar membranes.

Fact 1: Air pollution harms the respiratory and circulatory systems. 
Fact 2: An example of an air pollution reaction is the production of photochemical smog.
Smog harms the respiratory and circulatory systems.

Fact 1: Male dogs use pheromones in urine to mark their territory. 
Fact 2: All animals emit pheromones to mate.

Male dogs use urine to mark their territory the same way as they find mates.