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
Logistic growth
How does evolution affect life history traits?
Life history trait:
Reproductive strategies:
Typically occurs in
Much more common. Typically
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.