Population Dynamics

1. Population Dynamics

2. Objectives • The student will investigate and understand dynamic equilibrium within populations, communities, and ecosystems. • Key concepts include: • interactions within and among populations including carrying capacities, limiting factors, and growth curves;

3. Population Dynamics Population: all the individuals of a species that live together in an area Demography: the statistical study of populations, make predictions about how a population will change

4. 3 Key Features of Populations • Size • Density • Dispersion • (clumped, even/uniform, random)

5. 3 Key Features of Populations 1. Size: number of individuals in an area

6. 3 Key Features of Populations Growth Rate Birth Rate (natality) - Death Rate (mortality) How many individuals are born vs. how many die Birth rate (b) − death rate (d) = rate of natural increase (r).

7. Factors That Affect Future Population Growth Immigration + + - Population Mortality Natality - Emigration

8. Population Dynamics Addition of individuals to populations Removal of individuals from populations

9. 3 Key Features of Populations 2. Density: measurement of population per unit area or unit volume Formula: Dp= N Pop. Density = # of individuals ÷ unit of space S

10. Factors that Affect Density Immigration- movement of individuals into a population Emigration- movement of individuals out of a population

11. Factors that Affect Density Density-dependent factors-Biotic factors in the environment that have an increasing effect as population size increases Ex. disease competition parasites

12. Humans Are Not Exempt from Nature’s Population Controls • Ireland • Potato crop in 1845 • Bubonic plague • Fourteenth century • AIDS • Global epidemic (pages 161-162)

13. Factors that Affect Density Density-independent factors-Abiotic factors in the environment that affect populations regardless of their density Ex. temperature storms habitat destruction drought

14. Density-Independent Factors (e.g., weather) Good Times! (in Australia)

15. 3 Key Features Populations • 3. Dispersion: describes their spacing relative to each other • clumped • even or uniform • random

16. clumped even (uniform) random

17. Clumped Dispersion of Population Clumped dispersion implies some sort of cohesive force, e.g., either individuals seek other individuals out, or individuals are limited in where then can reside

18. Uniform Dispersion of Population Uniform dispersion implies some sort of antagonistic interaction, e.g., either individuals actively repel other individuals

19. Random Dispersion of Population Random dispersion implies a minimum of interspecific interactions that impact where individuals reside

20. Other Factors That Affect Population Growth Limiting factor-any biotic or abiotic factor that restricts the existence of organisms in a specific environment. • EX.- Amount of water Amount of food Temperature

21. Limiting Factor- Zone of Tolerance Few organisms present None Few organisms present None Many organisms present

22. Other Factors that Affect Population Growth Carrying Capacity-the maximum population size that can be supported by the available resources There can only be as many organisms as the environmental resources can support

23. No Population Can Continue to Increase in Size Indefinitely Biotic Potential = Intrinsic growth rate: Maximum potential for growth –occurs where there is unlimited resources

24. Logistic Growth of a Sheep Population on the Island of Tasmania, 1800–1925 Oscillations about K (the carrying capacity)_

25. Exponential Growth, Overshoot, and Population Crash of a Reindeer Irruptive Population Curve

26. Population Cycles for the Snowshoe Hare and Canada Lynx Boom and Bust Population Curve

27. 2 Life History Patterns • r Strategists • short life span • small body size • reproduce quickly • have many young • little parental care • Ex: cockroaches, weeds, bacteria

28. 2 Life History Patterns • K Strategists • long life span • large body size • reproduce slowly • have few young • provides parental care • Ex: humans, elephants

29. Idealized Survivorship curves

30. Survivorship Curves Three types of survivorship curves • late loss (Type I) Example: Humans • constant loss (Type II) Examples: Birds, Fish • early loss (Type III) Example: Mice

33. How is Population Data Gathered? Births minus Deaths Immigration and Emigration 1,345 – 645= 700 natural increase Age structure Diagrams • Tag and Recapture

34. The Human Population • Define the following vocabulary a. Total fertility level b. Replacement level fertility c. Infant mortality rate d. Doubling time e. Zero population growth

35. The Human Population • Who was Thomas Malthus and what did he predict?

36. Human Population Growth

37. Human Population Growth

38. World Human Population http://www.census.gov/ipc/www/worldpop.html

39. U.S. Human Population http://eire.census.gov/popest/archives/pre1980/popclockest.txt

40. Time unit Births Deaths Natural increase Year 130,013,274 56,130,242 73,883,032 Month 10,834,440 4,677,520 6,156,919 Day 356,201 153,781 202,419 Hour 14,842 6,408 8,434 Minute 247 107 141 Second 4.1 1.8 2.3

41. http://www.ibiblio.org/lunarbin/worldpop -

42. What is the formula for finding growth rate? r = b – d r = 26/1000 - 5/1000 r = 0.026 – 0.005 = 0.021 or 2.1% per year OR (the easy way) r = 26/10 - 5/10 r = 2.6 - .5 = 2.1 or 2.1% per year Growth Rate

43. Doubling Time • Rule of 70 – determines the number of years it will take a country’s population to double. Doubling time = 70/%growth rate Growth rate = 70/doubling time • Let’s practice: A country’s growth rate is 1.5%. How many years will it take that country’s population to double? 70/1.5 = 46.7 years

44. How do population pyramids help us learn about population?

45. Population pyramids are used to show information about the age and gender of people in a specific country. Male Female There is also a high Death Rate. In this country there is a high Birth Rate Population in millions This population pyramid is typical of countries in poorer parts of the world (LEDCs.)

46. In some LEDCs the government is encouraging couples to have smaller families. This means the birth rate has fallen.

47. Male Female In this country the number of people in each age group is about the same. Population in millions The largest category of people were born about 40 years ago. In this country there is a low Birth Rate and a low Death Rate. This population pyramid is typical of countries in the richer parts of the world (MEDCs.)

48. Male Female Population in millions In the future the elderly people will make up the largest section of the population in this country. In this country the birth rate is decreasing. This is happening more and more in many of the world’s richer countries.

49. Male Female Population in thousands This country has a large number of temporary workers. These are people who migrate here especially to find a job.

50. Population pyramid for Mozambique. Population pyramid for Iceland.