1. Lesson 4.3 Population Growth
From 1800 to today, the human population has grown from about 1 billion to more than 6.8 billion—an exponential rate of increase.

2. Lesson 4.3 Population Growth
Birth and Death Rates
A population’s relative birth and death rates (mortality and natality) affect how it grows.
Survivorship curves show how the likelihood of death varies with age.

3. Immigration and Emigration
Lesson 4.3 Population Growth
Immigration and Emigration
In addition to births and deaths, population growth is affected by immigration and emigration—individuals moving into and out of a population.
Migration, seasonal movement into and out of an area, can temporarily affect population size.

4. Calculating Population Growth
Lesson 4.3 Population Growth
Calculating Population Growth
Determined by the following equation: (birth rate + immigration rate) – (death rate + emigration rate)
Growing populations have a positive growth rate; shrinking populations have a negative growth rate.
Usually expressed in terms of individuals per 1000
Did You Know? Immigration contributes more than 1 million people to the U.S. population per year.

5. Lesson 4.3 Population Growth
Exponential Growth
Population increases by a fixed percentage every year.
Normally occurs only when small populations are introduced to an area with ideal environmental conditions
Rarely lasts long

6. Logistic Growth & Limiting Factors
Lesson 4.3 Population Growth
Logistic Growth & Limiting Factors
Growth almost always slows and stops due to limiting factors.
Limiting factors: Environmental characteristics slow population growth and determine carrying capacity.
Density-dependent: Influence changes with population density.
Density-independent: Influence does not change with population density.

7. Population Control Concept Map
Use the following words or phrases:
temperature
limiting factors
competition
habitat distribution
density-dependent
parasitism
disease
more intense as population increases
food supply
same regardless of population size
predation

8. Canadian Lynx vs. Snowshoe Hare
Rudolfo's Usenet Animal Pictures Gallery
Study done by Charles Elton.
Hare population underwent regular cycle, with 10 years between population peaks.
Peaks in lynx population cycle occurred near peaks of hare cycle.
Conclusion:
-More hares = More lynx
-Hare population decreases due to predation
-Lynx population decreases due to less prey
-Hare population rebounds as lynx population decreases
Problem: Hare populations on islands without lynxes still undergo regular cycles
Possible explanation: Lynx population depends on hare population, but hare population depends on other factors.
adapted from Odum, Fundamentals of Ecology, Saunders, 1953

9. Lesson 4.3 Population Growth
Biotic Potential
An organism’s maximum ability to produce offspring in ideal conditions
Many factors influence biotic potential, including gestation time and generation time.
Organisms with high biotic potential can recover more quickly from population declines than organisms with low biotic potential.

10. Bell Ringer
Get out your homework. I will come around and check it as you work today.

11. What to Turn In I will randomly collect one set from each group.
Procedure page with graph on back
Spread sheet
Limiting Factors table
Follow-up Questions and Conclusions
I will randomly collect one set from each group.

12. Bell Ringer
Place your homework on the front table.
Quiz today!!

13. Bell Ringer
Place your crosswords on the front table!