1. Announcements September 11, 2006 Study Abroad Program Africa/Asia/Middle East Open House Wednesday, Sept. 13 3:30 - 5:30 PM 101 International Studies Building

2. Announcements September 11, 2006 New handout available for students taking the course for honor’s credit. (additional assignment choice added) Make sure you come talk to me before starting your assignment!

3. Announcements September 11, 2006 Schedule for next week: Monday (Sept 18th) - brief review of what you need to know for first exam. Wednesday (Sept 20th) - first exam Friday (Sept 22) - no class

4. Which of these age distributions has a Type III survivorship curve? A BC Type III survivorship curve Very high mortality among the young

5. Which of these age distributions has a Type III survivorship curve? A Type III survivorship curve Very high mortality among the young

6. Type I survivorship curve Survival is high until old age Examples: Dall sheep Humans in developed countries

7. Type II survivorship curve Mortality is spread evenly among all age groups Example: Many species of birds

8. Type 1 Type 2 or 3

9. Carrying Capacity —Number of individuals of a species that can be indefinitely sustained in a given area.

10. Environmental Resistance Environmental Resistance—Any factor (limiting factor) in the environment influencing carrying capacity. Four main factors: –Raw material availability –Energy availability –Waste accumulation and disposal –Organism interaction

11. Logistic Equation Note: This equation is provided only to help. You do not need to memorize it. You will not be asked about the equation on a test.

12. Causes of population crashes Population size can sometimes overshoot carrying capacity Environmental resistance factors can change, lowering carry capacity When population > carrying capacity, death rates > birth rates Population crashes!!

13. Example 1: bacterial population crash due to toxic waste accumulation

14. Example 2: Population cycling due to organism interaction Hare population: birth rate limited by food availability death rate determined by predators, food Lynx population: birth and death rate determined by food availability (hares)

15. Example 2: Population cycling due to organism interaction Start: both have low population density Hares – high food, low predators = pop increase over next generations Lynx – as hares increase, more food = pop increase Hares – when high pop density, increased competition for food and increased predation = low birth rate & high death rate = sharp pop decrease Lynx – when high pop density and few hares, low food = low birth rate & high death rate = sharp pop decrease Back to start

16. Population Cycles

17. Remember: Several factors influence population growth rate: BirthrateDeath rate Sex RatioAge Distribution ImmigrationEmigration But, there are also additional things about the individuals that influence how the population grows

18. Life history traits – characteristics of an individual that influence survival and reproduction Age at maturity 11 - 20 years 3-6 years Atlantic Salmon African elephant 2 months House Mouse

19. Life history traits – characteristics of an individual that influence survival and reproduction Atlantic Salmon African elephant House Mouse 1 calf every 3-8 years 1,500 to 8,000 eggs once 5-8 young every month Number of offspring produced

20. Life history traits – characteristics of an individual that influence survival and reproduction Atlantic Salmon African elephant House Mouse Number of reproductive events ~3 - 10 1~6-12

21. Life history traits – characteristics of an individual that influence survival and reproduction Atlantic Salmon African elephant House Mouse Lifespan 60 - 70 years3-6 years ~2 years

22. How do the following life history traits affect the rate of reproduction? Age at maturity # offspring # reprod. events life span 2 momanyone long 2 yrfewmany short 2 momanymanylong 2 yrmanymanylong

23. K-strategists: Remember that “K” is Carrying Capacity long lived produce few offspring parental care Reproductive strategies and population fluctuations

24. –controlled by density-dependent limiting factors factors more severe as population increases example: food K-strategists: stable populations at carrying capacity (K) examples: humans (in theory), deer, lions Reproductive strategies and population fluctuations

25. Gypsy moth caterpillars Remember that “r” is population growth rate r = b - d r-strategists: small short life many offspring Reproductive strategies and population fluctuations

26. Gypsy moth caterpillars r-strategists: rarely reaches K little or no parental care Reproductive strategies and population fluctuations

27. Gypsy moth caterpillars –good at using temporarily abundant resources r-strategists: controlled by density-independent limiting factors: weather, pond drying Reproductive strategies and population fluctuations

28. Points to know: Understand the three types of survivorship curves. What factors influence population growth rates? What are some life history traits? Know the difference between K- and r- strategists and what kind of limiting factors each has.

29. Human Population Issues I Lecture Objectives Understand past and current human population growth trends and their impacts Understand the factors that affect human population growth Understand how social and political issues influence these factors

30. Human population growth Long lag phase, then exponential growth

31. Currently… 6.2 billion humans on Earth –tripled since 1900; 7.8 billion expected by 2025 Overall, 1.3% annual growth rate –54 years to double population if not decreased

32. Currently… Countries vary greatly in actual growth rate

33. Why should we care about human population growth rates? Human population growth contributes to: Famine Economic disparities increase, leading to increased political unrest Environmental degradation Water & air pollution Extinction of species Carrying capacity of Earth???????

34. What factors influence human population growth? Same as for other species: Birth rate Death rate Sex ratio Age distribution Immigration/emigration Density Study of these for humans called demography

35. Birth rates and Death rates

36. Sex Ratio Humans have roughly 1:1 sex ratio Total Fertility Rate – number of children a woman has during lifetime Replacement Fertility = 2.1 children/female/lifetime (leads to zero population growth in long term)

37. Age Distribution If total fertility rate immediately = 2.1, population would still increase for 20 years! “Aging population” fewer young, productive workers

38. U.S. Age Distribution over time “Baby boom” changes major societal concerns Housing, schools, supplies for children University education, large young workforce Child care, luxury items, productive working years Retirement, elderly heath care

39. Immigration/Emigration Of 1.1 % increase in U.S. pop, 0.5% is due to immigration Mexico loses an estimated 250,000 people per year to emigration Millions of people want to emigrate from war-torn, poverty-stricken countries to more stable, developed countries

40. Population Density Number of people per unit land area As density increases, more severe impacts on environment Density (people per sq mile*) India 733.2 China 320.9 US 68.7 Russia 22.7 *not all square miles equally productive

41. Population Density Distribution of people within countries also important. 47% of world’s population in cities, expected to increase to 60% by 2025 Problems with dense populations in cities: –Water transported long distances –Wastes difficult to get rid of –Decreased air quality –Large burden on local environment –Social unrest due to economic disparity

43. Social & political factors influence human population growth What determines how many children a woman has? What policies do countries have on population growth? Immigration?

44. Major social factors affecting birth rates 1. Cultural role/status of women –In male-dominated societies, traditional role of women is to marry & have children –Women not educated, encouraged to marry young –Lack of education makes women dependent on husband, children Women in developed countries educated, have option to delay marriage or not marry

45. Major social factors affecting birth rates 1. Cultural role/status of women, cont. –Early marriage = more child-bearing years = more children –% of births by 15-19 year olds: Africa 17% Latin America 16% All developed countries 3%

46. Major social factors affecting birth rates 2. Desires of women & access to birth control –Women in less-developed countries have more children than they want –Often little access to birth control, education on how to use –Religious views on birth control (http://www.cnn.com/2004/LAW/03/01/church.contraceptives.ap/index. html) However, women in less-developed countries want more children than women in developed countries. WHY?

47. Economic value of children In less-developed countries: Guard against high infant mortality Security in old age Labor force = desire for more children In developed countries: High probability of survival Large economic expenditure not put into retirement plan Increase labor by parents = desire for less children

48. Most important factors affecting population growth rates 1.Development of/access to modern birth control 2.Education of women

49. Political policies on population growth Encouraged in some countries (U.S., European) by subsidies: –Paid maternity leave –Guaranteed jobs –Childcare –Tax deductions –Birth bonus (Canada) Need younger workers to support aging populations

50. Political policies on population growth Discouraged in other countries with varying degrees of success China: 1. Due to slow economic growth, PRC began first population control measures in 1955 2. Campaign begun in 1971 - Raised legal age of marriage to 23 for women, 25 for men in rural areas and 25,28 in urban areas 3. One child limit started in 1978 4. Contraception and abortion readily available and widely used. Result: Current total fertility rate of 1.8

51. Political policies on population growth India: 1. Little government intervention until recently 2. Emphasizing improving quality of life - Decrease infant mortality to decrease desire - Encourage education for women Result: Current total fertility rate of 3.2 children (goal of 2.1 by 2010)

52. Effect of different policies Pop size (mil) % growth rate# added/year (mil) China1280.70.78.96 India1049.51.717.84 This is not an endorsement of the methods used by PRC to reduce births!!

53. Political policies on immigration Countries with low birth rates (European, Japan, China) may face shortage of workers without immigration Emigrants want to move to developed countries to improve standard of living –Tremendous pressure on Europe and N. America to accept immigrants –Significant numbers of immigrants can strain social systems

54. How many total children do you want to have? 1) 0-1 2) 2-3 3) 4-5 4) > 5

55. Points to know 1.Know the past, present, and projected future world population of humans 2.Know the human issues for each of the 6 factors that affect population growth rate 3.Why do women have more children in male-dominated societies and less children in developed countries? 4.What two changes have caused/will cause the greatest decrease in population growth rates? 5.How have political policies in China and India changed their population growth rates? 6.How do political policies on immigration affect growth rates? Why do many people want to emigrate?