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.
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Question: Sentence1: Specialization occurs when competing species evolve different adaptations. 
Sentence2: evolving different adaptations increases survival.

Answer: adaptations


Question: Sentence1: Fish are the first known true chordates. 
Sentence2: Fish are the first known animal with a backbone.

Answer: Fish


Question: Sentence1: Ice ages buried the planet in snow and ice for millions of years at a time. 
Sentence2: climate change can bury the planet in snow.

Answer:
snow