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: Cells vary in size as well as shape, but all cells are very small. 
Fact 2: Basic unit of the plant body is the cell.
Basic units of the plant body vary in size as well as shape, but all are very small.

Fact 1: Courtship is behavior that is intended to attract a mate. 
Fact 2: Almost all animals display colors to attract a mate or to scare off a predator.
Courtship can be manifested by displays of color.

Fact 1: wind is used for producing electricity. 
Fact 2: We also need gas and electricity for heating and lighting.

Power is produced from wind which is needed for lighting.