Organism

An organism is an individual living system that maintains itself through coordinated biological processes and performs the functions associated with life.

Cell: The smallest structural and functional unit of life, bounded by a membrane and capable of carrying out biological processes. In cellular life, cells are the basic units that compose an organism.
Cellular respiration: The set of processes by which cells extract usable energy from organic molecules. It shows how organisms convert food molecules into energy for cellular work.
Virus: An infectious entity made of genetic material and a protein coat that replicates only inside host cells. Viruses reproduce through host machinery but lack the independent metabolism typical of organisms.
Model organism: A species studied extensively to understand biological processes that may apply to other organisms. Model organisms let researchers investigate life processes in tractable, well-characterized systems.
Origin of life: The study of how life first arose from nonliving chemistry on the early Earth or elsewhere. Explaining life’s emergence may clarify which features make an entity an organism.
Tissue: A group of similar or coordinated cells that performs a shared function in a multicellular organism. Tissues organize cells into functional layers of an organism’s body.
Gene expression: The process by which information in a gene is used to produce a functional RNA or protein. Gene expression supplies many of the molecules that build and regulate an organism.
Prion: An infectious misfolded protein that propagates its shape by inducing misfolding in other proteins. Prions can spread and cause disease without cells, genes, or metabolism.
Species: A taxonomic unit used to group organisms by shared characteristics and evolutionary relationships. Species classification organizes the diversity of organisms into named biological groups.
Artificial life: The study and creation of systems that reproduce or simulate features of living systems. Artificial life tests whether organism-like functions can arise outside natural biology.

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