Analyzing Populations

Identify and describe the three ways to analyze population size

1. Counting = Works well for large visible relatively stationary organisms

2. Population Sampling = Grid out square meters randomly thought field, find average number of plants per square meter and multiply by square meter of field

3. Mark-Recapture Method = Set traps, count/mark/tag what you caught, release them, come back later and recapture

Population Growth Rate Equation

Change in population size over change in times equals birth rate minus death rate (add immigration and subtract emigration)

• dN = change in population size

• dt = change in time

• B = birth rate

• D = death rate

Survivorship Curve I

Most losses occur at older ages; most fatality for elderly; K-selected

Traits of K-Selected Species

• In Survivorship Curve I

• Longer life span

• Fewer offspring

• Iteroparity = multiple reproductions

• Parental care

• Larger sized animals

Survivorship Curve II

Equal chance of death at any time

Survivorship Curve III

Lots of offspring though most dies; those that survive live long; r-selected species

Traits of r-Selected Species

• Lots of offspring

• Semelparity = single reproduction

• No parental care

• Shorter life span

Exponential Growth

Slow initial growth (lag phase) then rapid increase of growth and will either experience a population crash or develop logistic growth

• R-selected species

• Survivorship Curve III

• Does not go on forever - will eventually hit a limiting factor

• Intrinsic rate of increase = maximum rate of reproduction

Conditions for Exponential Growth

• Ideal conditions for population

• All needed resources in abundance (food, water space)

• No predators, competition, disease, natural disaster

Exponential Growth Equation

Change in population size over change in time equals the maximum per Capita growth rate of a population times population size

• dN = change in population size

• dt = change in time

• r_^max = maximum per Capita growth rate of population

• N = population size

Cull the herd

Remove the weak, keeping remaining healthy and strong

Carrying Capacity (K)

The maximum number of organisms the population can sustain