TASK DEFINITION: Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
PROBLEM: Sentence1: Macroevolution occurs over geologic time above the level of the species. 
Sentence2: adding new genes with special capability occurs over geologic time above the level of the species.

SOLUTION: above

PROBLEM: Sentence1: With a spatula, fold in flour mixture. 
Sentence2: a sifter is used for separating flour.

SOLUTION: flour

PROBLEM: Sentence1: All animals are heterotrophs. 
Sentence2: All fish are heterotrophic.

SOLUTION:
heterotrophs