Which ideas are part of the organic theory of nations?

Borders do not exist permanently; states are organic and growing, and represent a temporary snapshot of the allegiances and identity of the people who inhabit a region.

The Organic Theory of geography -- or maybe more accurately, of geopolitics -- was proposed by German geographer Friedrich Ratzel in 1897.  He suggested that nations function similarly to living organisms.  The controversial part of his theory was that the way a living organism takes in nourishment to grow and thrive, strong nations naturally will nourish and expand themselves, taking in weaker nations or cultures around them.  Ratzel coined the term "Lebensraum" (German for "living space"), which originally, in his view, meant the space for a strong nationalist culture to grow.  His writings came only a few decades after the German Empire had been reborn as the "Second Reich" (second kingdom), a renewal of the older "Holy Roman Empire" of German states as they were linked together in the medieval era.  Ratzel's ideas about "Lebensraum" later were picked up by Hitler and the Nazis as a justification for expanding German territory and taking over neighboring countries.  Germany's expansion under the Nazis as the "Third Reich" led to World War II in Europe.