The study of population vital statistic and how they vary with age
Life table
Age-specific summary of the vital statistics of a population
Cohort
A group of individuals in a population born about the same time
Survivorship (Ix)
Proportion of individuals born that survive to age x
Survivorship curves
Type I: Low death rates during early and middle life and a sharp increase in death rates later in life
Type II: Constant death rate over the life span
Type III: High death rates for the young; death rate steeply declines for survivors of early period die-off
Reproductive table
An age-specific summary of the reproductive rates in a population
Exponential population growth
Growth of a population with continuous generations in an ideal, unlimited environment, represented by a J-shaped curve when population size is plotted over time
Geometric population growth
Growth of a population with discrete generations in an ideal, unlimited environment
Discrete generations
Generations that have no overlap in reproduction
Populations have the potential to expand greatly when resources are abundant
Unregulated population growth in discrete time intervals = geometric growth
Unregulated population growth in continuous time intervals = exponential growth
Changes in population size
Births + Immigrants entering population - Deaths - Emigrants leaving population = Change in population size
Net reproductive rate (R0)
R0 < 1, population is decreasing
R0 = 1, population is stable
R0 > 1, population is increasing
Instantaneous growth rate or intrinsic rate of increase (r)
r < 0, population is decreasing
r = 0, population is stable
r > 0, population is increasing
Exponential population growth results in a J-shaped curve
Unregulated population growth is characteristic of populations that are introduced to a new environment or rebounding after drastic reduction by a catastrophic event or experiencing a pulse of new nutrients
Increasing population size gives rise to shortages in food and other limiting resources, greater intraspecific aggression, increased attention from predators, and greater risk of disease outbreaks, which can lower birth rates and elevate death rates