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: Echinoderms use pheromones to communicate with each other. 
Sentence2: Echinoderms are known for their round symmetry.
Echinoderms

Sentence1: Water is essential for all life on Earth. 
Sentence2: H2O is needed for all life on Eartth.
Earth

Sentence1: Dates are provided for the recognized eras and periods of geologic time. 
Sentence2: Macroevolution above the level of the species is evolution over eras and periods.

eras