BIOL 290 Lecture Notes - Lecture 15: Life Table, Demographic Transition, Survivorship Curve
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Demography:
• Statistical study of populations; predict population growth or
decline
• Age Distributions
• Number of individuals of each age class represented in the
population
• Age classes; by year, or by sections
• Age pyramids: shows what's happening now, and in the past
(modified by mortality events); tells story of birth and death and
shows survivors from the past (baby boom 50 years ago)
o Spain
o United States
o Pakistan; children highest age class
• Wide base: high birth rate; most of the population is children
• High natality and high mortality= stable population; pattern
between these two determine whether the population is growing,
decreasing or is stable
• Rio Grande cottonwoods
• No recruitments; step mortality: will die out
Life Table: An age specific summary of survival
• Life tables are often constructed by following the fate of a cohort
(in terms of survival)
• What's their risk of dying?; invented by insurance companies
• Cohort: A group of individuals of the same age (or stage)
• Life Table Definitions
o Survivorship: