Survival curve

from Wikipedia, the free encyclopedia

A survival curve is the graphical representation of the death rate (mortality) of a population over time. Survival curves are mainly used in biology and clinical studies .

The survival curves for five different creatures ( human , elephant , crow , crocodile and dandelion ).
The survival curves of different mouse populations as a function of the calorie reduction .

description

The number of observed individuals is usually plotted on the ordinate (y-axis). In biology, a logarithmic division of the ordinate is usually used. Usually a linear percentage scale in clinical trials. The time is plotted on the abscissa (x-axis). In most cases with a linear scale. The data for a survival curve can be taken from a life table , for example .

There are three fundamentally different types of survival curves in biology:

  • Type I is characterized by a very low death rate for young and middle-aged individuals. Before reaching the range of the maximum life span, i.e. at an advanced age, the death rate then rises sharply. This type of survival curve is extremely rare in the wild. It is found in some animal species in captivity and in modern humans in industrialized nations.
  • With type II, the death rate is the same at any age. This shape of the curve can be observed , for example, in many bird species such as the white stork .
  • Type III is characterized by a very high mortality rate at a young age. In contrast, it decreases significantly in middle and old age. This curve can be observed in all living things with a very high number of offspring, such as frogs and dandelions . One speaks of living beings with an r-strategy (see: Reproduction strategy ). This type of survival curve is most common in nature.

These three types are idealized. They only approximate real survival curves. The American ecologist Edward Smith Deevey (1914–1988) made significant contributions to the survival curves of a number of animal species .

There are differently modified forms of survival curves in clinical studies. One of them is, for example, the Kaplan-Meier survival curve .

further reading

Individual evidence

  1. ^ MW Nabors and R. Scheibe: Botany. Pearson Education, 2007, ISBN 3-827-37231-3 , p. 628. Limited preview in Google Book Search
  2. ^ NA Campbell and JB Reece: Biology. Pearson and Benjamin Cummings Verlag, 2005, ISBN 0-805-36777-2 , pp. 1177f
  3. ↑ a b W. Nentwig et al.: Ecology compact. Verlag Springer, 2009, ISBN 3-827-42304-X , p. 68. Restricted preview in the Google book search
  4. ^ CR Townsend et al.: Ecology. Verlag Springer, 2009, ISBN 3-540-95896-7 , p. 193. Limited preview in the Google book search
  5. ^ Edward S. Deevey: Life Tables for Natural Populations of Animals . In: The Quarterly Review of Biology . tape 22 , no. 4 , December 1, 1947, ISSN  0033-5770 , p. 283-314 , doi : 10.1086 / 395888 , PMID 18921802 ( uchicago.edu [accessed March 27, 2018]).

Web links