Key Terms
Population
All individuals of a species in a given area that can interact.
Population size (N)
Total number of individuals in the population.
Population density
Number of individuals per unit area or volume.
Demography
Statistical study of population changes over time; includes birth rates, death rates, and life expectancies.
Direct count
Most accurate; often not logistically feasible.
Life table
Divides a population by age group and shows mortality rates and life expectancy at each interval.
Mortality rate formula
(Number dying in interval / Number surviving at start of interval) x 1000
Life history
The pattern of energy allocation across growth, maintenance, and reproduction over an organism's lifetime. Shaped by nat
Energy budget rule
Organisms must balance energy intake against the demands of metabolism, reproduction, and parental care. Spending energy
Semelparity
Reproduces once, then dies. Most energy dumped into one reproductive event.
Iteroparity
Multiple reproductive events over a lifetime.
Carrying capacity (K)
Maximum population size the environment can sustainably support.
Three phases of the S-curve
1. Exponential growth phase: population is small; resources are abundant 2.
Definition
Mortality factors that affect population regardless of density.
Age structure
The proportion of a population at each age range. Displayed as population pyramids.