A group of individuals of the same species living in a defined geographical area Population

To manage population size To understand genetic basis of evolutionary change –Populations are evolutionary units –Evolution = change in allele frequency of populations Why study this?

In this lab, we want to determine: 1: What is the density of individuals in the population? 2: Is population size increasing or decreasing? Imagining we are sampling a motile population, we can use mark-and-recapture to answer these questions.

What is density? Population size (N) per unit area (surface or volume) EXAMPLES: 5,000,000 diatoms/m 3 20,000 barnacles/m trees/ha 18.9 deer/mi 2

Factors that determine density in real populations

Survivorship What is it?

Survivorship curves Type I (means what?) Type II (means what?) Type III (means what?)

Survivorship Curves Plot the number (or percent) of individuals in a cohort still alive at each stage 3 general types hypothesized

Survivorship curves provide some life history information Life history: Traits that describe an organism’s life story in its environment. e.g. age at first reproduction, number and size of offspring, lifespan, etc.

Modeling Population Growth Exponential growth: unrestricted growth due to abundance of resources (e.g. food/space). Logistic: at a certain number of individuals, or the carrying capacity (K), population growth levels off due to limited resources

Modeling Population Growth Exponential growth: What are some examples? Logistic: What are some examples?