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: coal is used for generating heat by burning. 
Fact 2: Thus, the food is cooked by heat generated internally.
coal can be used to cook food.

Fact 1: Sponges have specialized cells called collar cells. 
Fact 2: Collar cells are the work horses of the sponge.
Sponges have specialized cells that are work horses.

Fact 1: Insects may live in large colonies and have complex social behaviors. 
Fact 2: Insect colonies Insect colonies are families because all members are close relatives.

Insects have more social behaviors because all family members are close relatives.