Leben

Leben, the German noun for life, denotes the condition that distinguishes living organisms from inanimate matter. In biology, life is commonly characterized by a set of criteria: organization into cells, metabolism, growth, reproduction, response to stimuli, homeostasis, and the capacity to evolve.

Origins: Most scientists locate the origin of life on Earth in the distant past, roughly 3.5 to 4 billion years ago, arising from chemical evolution that produced self-replicating systems. While the exact pathways are unknown, hypotheses include RNA world and metabolism-first models.

Diversity and categories: Life on Earth encompasses a wide range of organisms, from single-celled prokaryotes to multicellular plants and animals. A common dichotomy is prokaryotic versus eukaryotic life. Viruses challenge simple criteria for life because they depend on hosts for replication; whether they are alive depends on the definition used.

Processes and features: Living systems maintain order and function through metabolism and energy flow, typically via photosynthesis or respiration. They grow and reproduce, respond to environmental changes, and may migrate or adapt. Evolution by natural selection shapes diversity and complexity over generations.

Beyond biology, discussions of Leben intersect philosophy, ethics, and artificial life. Questions about consciousness, value of life, and the potential for non-terrestrial or synthetic life continue to inform science, theology, and policy. The study of Leben thus spans empirical research and conceptual inquiry.