Population Ecology Chapter: 52

What you need to know! 1. How density, dispersion, and demographics can describe a population. 2. The differences between exponential and logistic growth models. 3. How density-dependent and density independent factors can control population growth.

Levels of Organization From small to large: From small to large: Organism (individual) Organism (individual) Population – group of organisms of the same species that interact with one another Population – group of organisms of the same species that interact with one another Community Community Ecosystem/Biome Ecosystem/Biome Biosphere Biosphere

Population Characteristics Size* (N) = total number of individuals Size* (N) = total number of individuals Density* = number of individuals per area or volume (100 buffalo/km2) Density* = number of individuals per area or volume (100 buffalo/km2) *Dynamic – births/deaths & migration *Dynamic – births/deaths & migration Dispersion = grouping of Dispersion = grouping of individuals in area Clumped (humans in cities) Clumped (humans in cities) Uniform (nesting penguins) Uniform (nesting penguins) Random (trees in a forest) Random (trees in a forest)

Demographics – Life Tables Demographics is the study of vital population statistics Demographics is the study of vital population statistics Life Tables are age-specific summaries of survival patterns of a population Life Tables are age-specific summaries of survival patterns of a population

Demographics - Survivorship Curves Graph of Life Table Graph of Life Table Idealized survivorship curves show 3 common patterns of the relationship between age and death: Idealized survivorship curves show 3 common patterns of the relationship between age and death: Type I = Long Life Type I = Long Life Type II = intermediate; little to no relationship between age and death Type II = intermediate; little to no relationship between age and death Type III = Infanticide with longevity after adolescence Type III = Infanticide with longevity after adolescence

Demographics – Reproductive Table A fertility schedule that includes the relationship between age and reproductive success A fertility schedule that includes the relationship between age and reproductive success

Life History Traits that impact reproduction and survival Traits that impact reproduction and survival 1. Maturation 2. Frequency of reproduction 3. Clutch size Fecundity is the combination of 2 & 3 Fecundity is the combination of 2 & 3 Two evolutionary patterns: 1. Semelparity (big-bang reproduction) One massive reproductive event followed by death One massive reproductive event followed by death 2. Iteroparity (repeated reproduction) Several reproductive events throughout lifetime Several reproductive events throughout lifetime

Exponential Growth Maximum growth in ideal conditions Maximum growth in ideal conditions

Logistic Growth Realistic Model of Growth Realistic Model of Growth Carrying capacity (K) is the maximum amount of life an ecosystem can support Carrying capacity (K) is the maximum amount of life an ecosystem can support Usually density dependent and/or limiting factors Usually density dependent and/or limiting factors Fluctuations common Fluctuations common

Logistic Model & Life Histories r-selected species: r-selected species: Quick reproduction time leads to rapid increase in number (semelparity) Quick reproduction time leads to rapid increase in number (semelparity) Widespread death when K is reached Widespread death when K is reached K-selected species: K-selected species: Steady population around K Steady population around K Small number of large offspring needing intensive parenting Small number of large offspring needing intensive parenting Multiple reproductive events in lifetime (iteroparity) Multiple reproductive events in lifetime (iteroparity)

Limiting Factors Anything that reduces population growth Anything that reduces population growth Density-dependent factors apply as populations increase in density: Density-dependent factors apply as populations increase in density: Competition: food, water, territory, etc. Competition: food, water, territory, etc. Health (disease, waste) Health (disease, waste) Predation Predation Intrinsic factors Intrinsic factors Density-independent (abiotic) Density-independent (abiotic) factors apply to all populations, factors apply to all populations, regardless of size regardless of size Weather Weather Climate change Climate change Natural disasters Natural disasters

Population Dynamics Complex interactions between biotic and abiotic factors that cause variation in the size of a population Complex interactions between biotic and abiotic factors that cause variation in the size of a population Population are not stable; they fluctuate Population are not stable; they fluctuate Metapopulation includes the migration between more than one population Metapopulation includes the migration between more than one population

Human Population

Age Structure