2274. This #kanjipuzzle is about evolution. Start with one character, add a few strokes, and get another, then repeat. 一 -> ? -> ? -> ? -> 室

一 -> 十 -> 土 -> 至 -> 室  

一  ICHI, ITSU, hito(tsu) - one

十  JUU, tou, to - ten

土  DO, tsuchi - earth, soil

至  SHI, ita(ru) - utmost, arrive, lead to

室  SHITSU, muro - room