Organismen

Organisms are living systems that carry out the processes necessary for life, such as metabolism, growth, and reproduction. They range from single-celled bacteria to multicellular plants, animals, and fungi. Although highly diverse, organisms share a set of characteristics that distinguish them from nonliving matter: organized structure, energy transformation, interaction with their environment, and the ability to pass on genetic information to offspring.

Most organisms are cellular. Prokaryotes, including bacteria and archaea, consist of simple, nucleus-free cells. Eukaryotes, which encompass plants, animals, fungi, and many protists, have complex cells with a nucleus and specialized organelles. The three-domain classification system groups life into Bacteria, Archaea, and Eukarya, with substantial variation within each domain.

Organisms store genetic material in DNA. Some viruses also use RNA genomes, but they rely on host cells for replication, so they are not universally classified as organisms. Organisms reproduce, either sexually, or asexually, and populations evolve over time through natural selection and mutation.

Metabolism provides energy and building blocks for growth. Autotrophs such as plants and some bacteria capture energy from sunlight or inorganic sources to synthesize organic compounds, while heterotrophs obtain energy by consuming other organisms or organic matter. Organisms regulate internal conditions (homeostasis) and respond to stimuli.

Organisms populate every habitat on Earth, from oceans to deserts to polar regions. Their interactions create ecosystems and drive biogeochemical cycles. The study of organisms—taxonomy, systematics, and evolutionary biology—aims to classify diversity and understand their relationships and history.