Population Ecology  Size – represented by N  Density – number of individuals per area – 100 buffalo/km 2  Dispersion – how individuals are distributed – Clumped, uniform or random  Age structure – abundance of individuals at each age. Allows for predictions

Dispersion Patterns

Age structure diagrams

Survivorship Curves  Type I – most individuals survive to middle age. Then mortality is high. Humans  Type II – length of survivorship is random. Hydra  Type III – most die young (oyster)

Survivorship Curves

Population Growth 1. Biotic potential – growth rate of the population under ideal conditions Age at reproductive maturity Age at reproductive maturity Clutch size Clutch size Frequency of reproduction Frequency of reproduction Reproductive lifetime Reproductive lifetime Survivorship of offspring Survivorship of offspring

Carrying Capacity 2. Carrying capacity – the maximum number of individuals that can be sustained in a habitat 3. Limiting factors – factors that prevent a population from reaching its biotic potential Density dependent factors – increase as density increases. Ex. Parasites, competition, toxic waste, predation Density dependent factors – increase as density increases. Ex. Parasites, competition, toxic waste, predation Density independent factors – natural disasters Density independent factors – natural disasters

Growth Patterns  Exponential growth – reproductive rate is always above zero – J-shaped curve  Logistic Growth – when limiting factors restrict population size

Exponential Growth

Logistic Growth

Predator/Prey

Life Strategies  r-selected species – exhibits rapid growth – quickly invade a habitat, reproduce, then die. Many offspring, small, require little parental care. Ex. Insects  K-selected species – size remains constant, small numbers of offspring, extensive parental care. Ex. Humans, elephants