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: Dromaeosaurs are part of the theropod group of dinosaurs. 
Sentence2: Birds evolved from a group of bipedal dinosaurs that included Dromaeosaurs.
Dromaeosaurs

Sentence1: Ions are atoms or groups of atoms that carry a positive or negative electrical charge. 
Sentence2: An ion is formed after a neutral atom loses an electron.
Ions

Sentence1: Serious questions remain regarding what happens if endangered populations continue to decrease. 
Sentence2: harming an animal species causes that animal's species to become endangered.

endangered