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: moss causes chemical weathering. 
Sentence2: If the moss was completely dried then it is dead.

SOLUTION: moss

PROBLEM: Sentence1: a compass is used for determining direction. 
Sentence2: magnets can be used to determine direction.

SOLUTION:
determining