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.

Sentence1: Ribosomes are small organelles where proteins are made. 
Sentence2: Ribosomes are assembled inside the nucleus.
Ribosomes

Sentence1: Mitosis is cell division. 
Sentence2: mitosis often causes growth.
Mitosis

Sentence1: cutting down trees has a negative impact on an ecosystem. 
Sentence2: And, trees provide habitat for birds and animals.

trees