1. Ecology II: Communities and Populations

2. Population: the total number of a certain species in a given area

3. 3 Characteristics of Populations

4. 1. Geographic Distribution

5. 2. Population Density

6. 3. Growth Rate

7. I. Population Growth Affected by 3 Factors:

8. 1. Number of Births

9. 2. Number of Deaths

10. 3. Number of Individuals entering or leaving

11. Population Dynamics

12. Wolves in Yellowstone

14. Size, Distribution, Density

15. Size -Fluctuates constantly -Influenced by many factors -Growth = - (b-d) (i-e)

16. Distribution -Provides clues about environmental/social factors that affect populations 3 Types: 1.Clumped 2.Uniform 3.Random (rare)

17. Density -Number of individuals per unit area -May indicate resource availability

18. II. Population Demographics - The study of how population factors change over time

19. A. Density Dependent Factors -Affects populations as density varies Ex. -disease -predation -Limiting Resources 1.Food (nutrients) 2.Water 3.Space 4.Habitat

20. B. Density Independent Factors -Often abiotic -Natural disasters -Non-communicable disease

21. Population Growth Curves

22. Exponential Growth: populations reproduce at a constant rate Occurs when resources are unlimited

23. Logistic Growth: slowing or stopping of population growth after exponential growth Occurs when resources become scarce

24. Carrying Capacity: the largest number of individuals that an environment can support

25. Decline Phase: the population crash due to several causes Causes for Decline: 1.Stress 2.Disease susceptibility 3.Predation 4.Competition 5.Parasitism

26. Sampling: estimating size and density Forms: 1.Quadrat: small section of land, count individuals, extrapolate 2.Transect: a line across different areas 3.Mark-and-recapture: Catch as many as possible, mark them, repeat, marked/new total

27. III. Human Population Growth

28. History: -population grew slowly for thousands of years -disease kept the population low -most of history – 50% of children died -500 years ago human population began growing -invention of agriculture -increased food supply -improved sanitation, health care -exponential growth

30. Reasons for growth:

31. 1. Invention of Agriculture

32. 2. Increased food supply

33. 3. Improved sanitation and healthcare