Objectives:

1. Objectives: • To define and understand: • Population biology • Characteristics of populationspopulations grow • To estimate how pop’ns grow • initially w/ unlimited resources (exponential growth) • then as resources become limited (logistic growth) • What limits growth? • What are patterns in survivorship? • Trade-offs between growth, reproduction and parental care • Human population growth

2. Definition of Pop’ns = What are characteristics of the pop’n?

3. How is growth rate determined? Measuring pop’n size (N). Census/count individuals Δ N = (Δ B - D) + (Δ I - E) survival and reproduction are key factors that determine change in N Growth of pop’n = change in # of individuals over time; G • Must calculate birth and death rates (b & d) • Find the rate of increase = r • Use r to estimate pop’n growth (G) for one time period = r N

5. The biotic potential of pop’n • Depends on:

6. Age structure

7. Exponential growth implies unlimited resources • But, limits on pop’n growth exist • Carrying capacity (= K) • Environmental resistance • Logistic growth; G= r N [(K-N)/K] • What happens when N > K, N = K, N < K?

8. Density-dependent and density independent limiting factors: Pop’n may temporarily increase above carrying capacity Overshoot usually followed by a dramatic crash

9. Trade-off between births and density - as density increases births decrease

10. Size of pop’ns may fluctuate with regularity. • Usually caused by multiple factors • Snowshoe hare-lynx example:

11. Three types of survivorship curves Type I – Type III - Type II –

12. Trade-offs between: 1) frequency of reproduction, 2) # of offspring, and 3) parental care. • Big-bang reproduction • Repeatedreproduction

13. Human pop’n growing exponentially • Humans alter rate of increase; how? • Humans alter environmental resistance; how?

14. Largest countries: China, India, U.S. • Worldwide >6 b. today (r = 0.013) • In 2050 ~10 b? • Rapid growth in U.S. (1.8 % annually) • b and I • U.S. 300 m (~265 m 2003); now? • 2050, ~392 m