Aging

Aging is the gradual biological change over time that increases vulnerability to many diseases and functional decline. It occurs across organisms and involves interacting changes at molecular, cellular, and physiological levels.

Cellular senescence: A state in which cells permanently stop dividing while remaining metabolically active. Senescent cells accumulate with age and can release signals that disrupt nearby tissues.
Lifespan: The duration of an organism’s life, often measured from birth to death. Aging describes change over time; lifespan measures how long that process lasts.
Calorie restriction: A sustained reduction in energy intake without malnutrition. It extends lifespan in several model organisms and is studied as a possible aging intervention.
Antagonistic pleiotropy: An evolutionary hypothesis that genes beneficial early in life can have harmful effects later. It explains how natural selection can favor traits that contribute to aging after reproduction.
Telomere: A repetitive DNA-protein structure that protects the ends of linear chromosomes. Telomere shortening during repeated cell division can trigger senescence in some cells.
Healthspan: The portion of life spent in good health and without major disability. Aging can shorten healthspan even when lifespan changes little.
Rapamycin: A drug that inhibits mechanistic target of rapamycin signaling and suppresses immune activity. Rapamycin extends lifespan in several animal models, motivating trials of its effects on aging.
Disposable soma theory: An evolutionary theory that organisms allocate limited resources between reproduction and bodily maintenance. It explains aging through trade-offs between reproductive investment and long-term repair.
DNA damage: A physical or chemical alteration to DNA that can disrupt its structure or sequence. Damage accumulates with age when cellular repair does not fully restore genomes.
Homeostasis: The regulation of internal conditions within ranges compatible with biological function. Age-related loss of regulatory resilience makes it harder to restore stable internal conditions.

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