1. Population
Ch. 5

2. Characteristics of Populations
Geographic distribution
Population density
Growth rate

3. Population Size Affected by: Number of births Number of deaths
Number of individuals that enter or leave a population.
( immigration vs. emmigration)

4. Affecting Other Populations
Factors that limit one population in a community may also have an indirect effect on another population.
Ex: lack of water affects the growth of grass, reducing the number of seeds produced. The mice population have less food, the hawks have less food, and so on.

5. Exponential Growth
Exponential growth occurs when the rate of a population growth in each new generation is a multiple of the previous generation.
Bacteria growth: let’s look at it.
Will you work for pennies? Activity.
Growth rate = change in number of individuals
Time period

6. Logistic Growth
As resources become less available, the growth of a population slows or stops.
Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth.
Tutorial

7. Exponential Growth Meets the Real World
Limiting factor is any biotic or abiotic resource in the environment that limits the size of a population.
Carrying capacity is the number of individuals in a population that an environment can support over a long period of time.

8. Limiting Factors
Environmental factors such as food availability and temperature that affect an organism’s ability to survive in its environment are limiting factors.
Limiting factors can be biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms.

9. Limits on Population Growth
Limiting factors either cause a decrease in birth rate or an increase in the death rate.

10. Density-Dependent limiting factors
Factors become limiting only when the population density (# of org. per unit space), reaches a certain level.
Gypsy moths and zebra mussels
Ex:
Predation
Increase predators- decrease prey
Disease
More dense population- limited growth
Competition
Competing for resources

11. Density- Independent Limiting Factors
Factors that affect all populations in the same way, regardless of density.
Ex:
Weather
Seasonal Cycles
Natural Disasters
Human Activities

12. Human Population Growth
Human population was very slow for thousands of years.
Between 1650 and 1850 the population doubled, passing the 1 billion mark.
After 1850, it only took 80 years to double to 2 billion.
4 billion 45 years later.
It is estimated that the human population in now increasing 90 million people a YEAR.
Far more people are born than are dying. 3x as many.

13. Patterns of Population Growth
Demographic Transition- dramatic change in birth and death rates.
What do you think the trend is now with birth and death rates?
Age-structure diagrams- graph number of people in different age groups in the population.
What event is shown in the next age-structure diagram?

15. What is the future like for population growth?

16. Population Growth Review
Click on the following link and choose your text book. Review the links and take the self-test.
Ch. 5 Review