instruction:
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.
question:
Sentence1: Populations Populations are subsets of a species. 
Sentence2: Gene flow occurs when individuals move into or out of a subset of a species.
answer:
species


question:
Sentence1: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: Common fossils include plant fossils like ferns.
answer:
plant


question:
Sentence1: bacteria cause food to spoil. 
Sentence2: Food poisoning occurs when spoiled food is eaten.
answer:

spoil