sentences:  He is remembered, among other things, for Schmalhausen's law, which states that a population at its limit of tolerance in one aspect is vulnerable to small differences in any other aspect.Ivan Ivanovich Schmalhausen was born in Kiev, Russian Empire (now Ukraine) on April 23, 1884 to Luise Schmalhausen (Luisa Ludwigovna Schmalhausen) and Johannes Theodor Schmalhausen (1849–1894).His father was one of the founders of Russian paleobotany.