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: Any antigen that causes an allergy is called an allergen. 
Fact 2: Asthma attacks are caused by allergies.
Allergens can trigger asthma attacks.

Fact 1: Soil can be depleted of nutrients. 
Fact 2: For the nonrenewable resources, depletion means extraction of the available natural resources.
soil nutrition can be extracted.

Fact 1: Many consumers feed at more than one trophic level. 
Fact 2: Consumers are heterotrophs that feed on tissues of other organisms.

Heterotrophs may eat other organisms at more than one trophic level.