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Survivorship Curves

Survivorship Curves. Survivorship Curve:. A graph that represents the data in a life table , an age-specific summary of the survival pattern of a population. It plots the proportion or the number of survivors in the population for every age.

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Survivorship Curves

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  1. Survivorship Curves

  2. Survivorship Curve: • A graph that represents the data in a life table, an age-specific summary of the survival pattern of a population. • It plots the proportion or the number of survivors in the population for every age. • Answers questions like: How long do we live? How long do individuals in other species live? Do most individuals in a particular population die young or live to an old age?

  3. Idealized Survivorship Curve Specific points allow exact number of survivors to be visible Types I, II, and III all have varying life spans and survivorship curves compare them

  4. Types of Survivorship Curves • Type I: flat at the start, reflecting low death rates during early and middle life. Drop steeply past a certain threshold as death rates increase among older age groups. Examples: humans and many large mammals

  5. Types of Survivorship Curves • Type 2: Intermediate with a constant death rate over an organism’s life span. Examples: squirrels and other rodents, vertebrates, some lizards and some annual plants

  6. Types of Survivorship Curves • Type 3: High death rates when young but it flattens out as death rates decline for those few individuals who survived early on. Examples: long-lived plants, many fishes, marine invertebrates, oysters

  7. Determinants of Population Size In Populations not experiencing emigration or immigration, the determinants are… • Reproductive rate • Survivorship

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