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.

Q: Sentence1: harming an animal species causes that animal 's population to decrease. 
Sentence2: Oil spill sare harmful to animals and the enviroment.

A: harming
****
Q: Sentence1: Sex hormones are chemical messengers that control sexual development and reproduction. 
Sentence2: Androgens are male sex hormones.

A: Sex
****
Q: Sentence1: Cell division is more complex in eukaryotes than prokaryotes. 
Sentence2: Eukaryotes have more complex mitosis than prokaryotes.

A:
complex
****