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What are the 3 types of Survivorship curves in Ecology?

Definition of Survivorship curve:

A survivorship curve is a graph showing the number or proportion of individuals surviving to each age for a given species or group

For making survivorship curves, ecologists identify a cohort, which is a group of individuals of the same species, in the same population, born at the same time.

It provides information regarding different population parameters like lifespan, survival rate, mortality rate of a particular population of a species.

Population ecologists have classified 3 types of  Survivorship curves Type I, Type II and Type III.

3 Types of survivorship curves

Type I (Convex curve)

  • Late loss, high mortality rate after reaching old agae
  • High survivorship throughout life till old age sets in
  • Majority reaches maturity
  • Typical of k selected species with very few offspring’s.  See r-selected vs k selected species

Eg: Elephants, Humans, annual plants

Type II (Diagonal curve)

  • Constant loss or death rate independent of lifespan
  • Independent of age

Eg: Birds, rodents, Hydra, perennial plants

Type III (Concave curve)

  • Early loss, high mortality during younger age
  • Low mortality after maturity,
  • Typical of r -selected species with numerous offspring’s

Eg: Oysters, Small fishes, trees, Insects

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