Population Growth Chapter 14, sections 3, 4, and 5

Density Population density is a measurement of the number of individuals living in a defined space. # of individuals / area = population density

Geographic Dispersion Population dispersion is the way in which individuals of a population are spread out in an area. Uniform dispersionRandom dispersionClumped dispersion

Population Disperson Clumped: individuals may live close together for mating, protection, food Uniform: territoriality / competition for limited resources cause individuals to live at specific distances from each other Random: individuals spread randomly within the area

Survivorship Curves Number of surviving members over time

Survivorship Curves – Type I Type I (i.e. – humans): –Common for large mammals –Low infant mortality –Population generally survives to old age –Most parents care for young (protection of young ensures they survive to adulthood

Survivorship Curves – Type II Type II Curves –Birds, small mammals, some reptiles –Survivorship is roughly the same throughout organism’s life (equal chance of living and dying)

Survivorship Curves – Type III Type III –High birth rate –High infant mortality rate –Invertebrates, fish, amphibians, plants –Many will die from predation –Some will survive to adulthood

Changes in Population Size Increase in Population Size –Immigration – movement of individuals INTO a population –Birth – additional individuals born Decrease in Population Size –Emigration – movement of individuals OUT of population –Death – individuals dying

J Curves (Exponential Growth) Exponential Growth Curve –Occurs when resources are abundant –Rapid growth occurs –Can occur when non- native species is introduced to environment –Often crashes when population outstrips resources

S Curves (Logistic Growth) Logistic Growth Curve: –Brief period of slow growth –Brief period of exponential growth –Leveling off at a stable size

Carrying Capacity Maximum number of individuals of a particular species that the environment can normally and consistently support. This can change with changes in environmental conditions When capacity suddenly drops, the population can crash Carrying capacity

Limiting Factors: Factors that limit the size of a population Two types: –Density – Dependent (generally biotic) –Density – Independent (generally abiotic)

Types of Limiting Factors Density Dependent: those whose impact worsens as the density of the population increases –Competition –Predation –Parasitism and disease Density Independent: those whose limiting impact happens regardless of the population density –Unusual weather –Natural disasters –Human activities

Predator – Prey Populations of predators and their prey are closely linked – as the prey population rises, the predator population rises shortly after….then the prey population decreases and shortly after, the predator population decreases