Ecology: Populations

How are populations structured?

How are populations affected by the environment?

Where are we?

How populations grow: Theory

Organisms enter a population in 2 ways:

Organisms leave a population in 2 ways:

Model 1: Exponential Growth

The growth of a population continues indefinitely.

Assumes

Described by

(r): the “ “ how many offspring per individual in the population

As long as (r) is a positive value –

Higher (r) values will lead to

If (r) is 0,

If (r) is negative,

Model 2: Logistic Growth

The growth of a population decreases as the population approaches the

Models

The effect of (K) on (r)

Comparing exponential and logistic growth models for a population.

How populations grow: Reality

How are real populations structured?

Measuring population size – it can be difficult to do accurately!

Mark-Recapture method

Population Distribution – Individuals tend to be distributed in three major patterns:

Population Demographics

Demographics:

Demographic data can be arranged in tables

There are three major types of survivorship curves demonstrated in real populations:

How do real populations grow?

Exponential growth Typically occurs in

Logistic growth Much more common. Typically

How does evolution affect life history traits?

Life history trait:

Reproductive strategies:

Parental care

r-Selected vs K-Selected

How does the environment affect population growth?

The effect of population density on population growth.

Density Dependent Population Regulation

Human Population Growth – the underlying root of all anthropogenic ecological problems

Historical Human Growth Rate

The decrease in growth rate is not uniform across the globe.

As countries industrialize,

It is, as of yet,

Make sure you can …

… explain how populations can be mathematically modeled.

… describe relationships among all terms in population models.

… compare ideal populations to real-world populations.

… explain patterns of life-history, distribution and survivorship.

… explain the costs and benefits of particular life-history characteristic adaptations and strategies.

… describe historical and current trends in human population.