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Longevity is difficult to measure in wild animals and values for captive specimens may not be representative.
Summary of Sections 6.1 and 6.2
Survival plots summarize the mortality pattern of a particular species. Those of closely related species can differ greatly.
Summary of Sections 6.1 and 6.2
Ageing (senescence) is an intrinsic cause of death; extrinsic factors from the environment include starvation, disease, predation and accidents.
Summary of Sections 6.1 and 6.2
Organisms that produce many offspring at an early age have shorter lives than similar species that delay reproduction, i.e. there is a trade-off between longevity and reproduction.
Summary of Sections 6.1 and 6.2
Life histories can be characterized as mixtures of properties that maximize population growth rate or carrying capacity.
Summary of Section 6.3
Theory predicts that long-lived iteroparous organisms can increase their fitness by limiting or delaying reproduction in early life. In species in which reproductive success is strongly correlated with body size, breeding may be delayed until large body size has been achieved.
Summary of Section 6.3
A cost of delayed breeding is a reduced probability of surviving to breed at all. In some species, these effects have led to marked differences in the life history and longevity of males and females.
Summary of Section 6.3
Observational and experimental evidence reveal a trade-off between survival and reproduction: the energetic and other costs of reproduction reduce annual survival and thus longevity.
Summary of Section 6.3
As individual animals get older, they acquire skills that increase their reproductive success, and they invest more in reproduction; however, in older individuals these effects are countered by reproductive senescence.
Summary of Section 6.3
Within their lifespan, organisms may limit their reproductive effort in one year and so increase their reproductive success in subsequent years.
Summary of Sections 6.3
Longevity and reproductive strategy vary within a species as well as
differing between species. Some of the differences are genetic.
Summary of Sections 6.4 and 6.5
Artificial selection for longevity in short-lived laboratory animals increases
mean lifespan by as much as twofold.
Summary of Sections 6.4 and 6.5
Frequent experience of internal fertilization per se, as well as the trade-off
between body maintenance and egg production, reduce the lifespan of
females that breed.
Summary of Sections 6.4 and 6.5
In some animals, there is a trade-off between reproductive success and immune function.
Summary of Sections 6.6 and 6.7
Secondary sexual characters may indicate a male’s capacity to resist parasites and pathogens.
Summary of Sections 6.6 and 6.7
Salmon have two alternative life histories determined in part by genes but also by growth and social status early in life.
Summary of Sections 6.6 and 6.7
A few other long-lived mammals as well as humans undergo menopause, a post-reproductive state about whose adaptive significance several hypotheses have been proposed.
Summary of Sections 6.6 and 6.7
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