Friedrich Ratzel was a German geographer and ethnographer, born in 1844 and known for his contributions to the field of human geography. He is best recognized for developing the concept of Lebensraum, which refers to the idea that a nation requires territory to grow and thrive. His work laid the foundation for later geographical theories and influenced various disciplines, including political science and sociology. Ratzel's most notable publication, "Anthropogeographie," explored the relationship between human societies and their environments. He emphasized how geography shapes cultural and social development. His ideas have had a lasting impact on geography and have been both influential and controversial in the study of human-environment interactions.