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: disease-causing microbes have a negative impact on the body. 
Sentence2: pathogens have a negative impact on the body.

A: body
****
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: Sperm had to swim from male to female reproductive organs for fertilization. 
Sentence2: If fertilized, the egg implants itself in the uterus.

A:
fertilization
****