1. Population Ecology

2. How do Ecologist study populations?
Geographic range
Density and distribution
Random
Uniform
clumped
Growth rate
Age structure

3. Population growth Birth rate versus Death rate
Immigration versus emigration

4. Exponential growth Larger the population grows, the faster it grows
Organisms that reproduce rapidly
Organisms that reproduce slowly
Organisms in new environments
“j” shaped curve

6. Population Questions
Your rich uncle has just died and has left you 1 billion dollars. If you accept the money you must count it for eight hours a day at the rate of one dollar per second. When you are finished counting, the billion dollars will be yours and only then may you begin to spend it.
Do you accept your uncle’s offer? Why or why not?
How long would it take to count a billion dollars at this rate? How long would it take to count a million dollars at the same rate?

7. Doubling time
Bacteria multiply by division. One bacterium becomes two, two become 4, 4 become 8… For some bacteria, the time for this division process is 1 minute.
If you put one of these bacterium in a bottle at 11:00pm, the entire bottle will be full at 12am. When would the bottle be half full?

8. Logistic growth “s” shaped curve
As resources become limited, population growth slows or stops, leveling off at the carrying capacity.
Follows exponential growth
Carrying capacity – max. number of individuals of a particular species that a particular environment can support

10. Limiting factors to population
Separately or together, limiting factors determine the carrying capacity of an environment for a species.
Competition
Predation
Parasitism and disease
Unusual weather
Natural disaster

11. Density dependent vs. Density independent
Density dependent limiting factors affect density (# of organisms per unit area) when density reaches a certain level.
Competition, predator/prey, parasitism
Density independent factors – occur regardless of population size
Weather, natural disasters

12. Human Population Tends to increase Exponential growth
Less predators/disease
Improved nutrition, sanitation, medicine and health care
Exponential growth
Thomas Malthus predictions, population can only be limited by war, famine and disease

14. Patterns of human growth
Demography – scientific study of human populations.
use birthrates, death rates and age structure to predict growth or decline
Demographic transition
Change from high birthrates and death rates to low birthrates and death rates.
Japan, US and Europe have completed the transition
South America, Africa and Asia are in stage 2