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The two theories; non-adaptive, and adaptive, are used to explain the evolution of senescence, which is the decline in reproduction with age. [8] The non-adaptive theory assumes that the evolutionary deterioration of human age occurs as a result of accumulation of deleterious mutations in the germline. [8]
Senescence (/ s ɪ ˈ n ɛ s ə n s /) or biological aging is the gradual deterioration of functional characteristics in living organisms. Whole organism senescence involves an increase in death rates or a decrease in fecundity with increasing age, at least in the later part of an organism's life cycle.
Such an ageing process may include qualitative and quantitative changes and includes diminished or defective synthesis of collagen and elastin in the dermis. [citation needed] Extrinsic ageing of skin is a distinctive declination process caused by external factors, which include ultra-violet radiation, cigarette smoking, air pollution, among ...
[4] [5] [6] This process is known as "replicative senescence", or the Hayflick limit. Hayflick's discovery of mortal cells paved the path for the discovery and understanding of cellular aging molecular pathways. [7] Cellular senescence can be initiated by a wide variety of stress inducing factors.
In biogerontology, the disposable soma theory of aging states that organisms age due to an evolutionary trade-off between growth, reproduction, and DNA repair maintenance. [1] Formulated by British biologist Thomas Kirkwood , the disposable soma theory explains that an organism only has a limited amount of resources that it can allocate to its ...
In life history theory, evolution works on the life stages of particular species (e.g., length of juvenile period) but is also discussed for a single organism's functional, lifetime adaptation. In both cases, researchers assume adaptation—processes that establish fitness. [5]
This is an accepted version of this page This is the latest accepted revision, reviewed on 2 February 2025. Biological process of getting older This article is about ageing specifically in humans. For the ageing of whole organisms including animals, see Senescence. For other uses, see Ageing (disambiguation). Part of a series on Human growth and development Stages Gamete Zygote Embryo Fetus ...
Aging is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. The hallmarks of aging are the types of biochemical changes that occur in all organisms that experience biological aging and lead to a progressive loss of physiological integrity, impaired function and, eventually, death.