1. Chapter 6 Population and Community Ecology

2. Nature exists at several levels of complexity

3. Population Ecology Populations are dynamic Difference is between inputs and outputs Why is population ecology important?

4. Factors that Regulate Population Abundance and Distribution Population size (N )- the total number of individuals within a defined area at a given time. In 1987, California Condor had N = 22 Population ecologists caught all 22, in 2009, N = 300

5. Factors that Regulate Population Abundance and Distribution Population density- the number of individuals per unit area at a given time. Helps scientists figure out if species is rare or abundant Management zones – typically more hunting/fishing licenses for area with high pop. density

6. Factors that Regulate Population Abundance and Distribution Population distribution- how individuals are distributed with respect to one another. Random – no pattern Uniform – common in territorial organisms, toxic plants Clumped – schooling fish, flocking birds, herd animals

7. Factors that Regulate Population Abundance and Distribution Population sex ratio- the ratio of males to females - Typically 50/50 - Helps predict number of offspring in the next generation

8. Factors that Regulate Population Abundance and Distribution Population age structure- how many individuals fit into particular age categories. - Helps predict how rapidly a population can grow.

9. Factors that Influence Population Size Density-dependent factors- the size of the population will influence an individual’s probability of survival. - Examples: amount of available food

10. Factors that Influence Population Size Gause’s experiment demonstrates how food supply controls population growth Limiting resources - Examples: food, water nest sites, nitrogen, phosphorus Carrying capacity (K)

11. Factors that Influence Population Size Density-independent factors- the size of the population has no effect on the individual’s probability of survival. - Example: tornado, hurricanes, floods, fires

12. Exponential Growth Model Growth rate- the number of offspring an individual can produce in a given time period, minus the deaths of the individual or offspring during the same period. Intrinsic growth rate- under ideal conditions, with unlimited resources, the maximum potential for growth.

13. Exponential Growth Model J-shaped curve- when graphed the exponential growth model looks like this.

14. Logistic Growth Model Logistic growth- when a population whose growth is initially exponential, but slows as the population approaches the carrying capacity. S-shaped curve- when graphed the logistic growth model produces an “S”.

15. Variations of the Logistic Model If food becomes scarce, the population will experience an overshoot by becoming larger than the spring carrying capacity and will result in a die-off, or population crash.

16. Reproductive Strategies K-selected species- the population of a species that grows slowly until it reaches the carrying capacity. Ex. elephants, whales, and humans. R-selected species- the population of a species that grows quickly and is often followed by overshoots and die-offs. Ex. mosquitoes and dandelions

18. Survivorship Curves