APES 3.3 Survivorship Curves
Enduring Understanding:
- Populations change over time in reaction to a variety of factors
Learning Objective:
- Explain survivorship curves.
Essential Knowledge:
- A survivorship curve is a line that displays the relative survival rates of a cohort â a group of individuals of the same age â in a population, from birth to the maximum age reached by any one cohort member. There are Type I, Type II, and Type III curves.
- Survivorship curves differ from K-selected and r-selected species, with K-selected species typically following a Type I or Type II curve and r-selected species following a Type III curve.
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\ Type I
- Deaths occur at limit of biological life span
- low mortality at birth, high probability of surviving to old age
- humans - advancement in nutrition, prenatal care, disease prevention/cures, have allowed for longer life spans
- annual plants, elephants, humans
\ Type II
- death rate always uniform for any organism at any age
- still K-selected for the most part
- predation is primary means of death, affecting all age ranges
- reach adult stages quickly
- rodents, songbirds, perennial plants
\ Type III
- Death prevalent for younger members of species, often by predation and habitat loss
- death rates decline with age
- little to no care for babies
- species tend to have large numbers of offspring, reproduce for majority of their lifetime
- sea turtles, oysters, trees
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