1. Bellwork
Explain the changes in both numbers and rates of growth in the following population growth curves

2. Exponential vs. Logistic Growth
Exponential growth occurs when resources are not limiting.
Logistic growth occurs when resources become more and more limiting as population size increases.

3. Category 4: Population and Resource Use

4. Population
Population Biology
Human Population

5. Characteristics of Populations
In terms of dispersion, individuals of a population can be clumped*, uniform, or randomly distributed.

6. 2Population Dynamics & Carrying Capacity
Population size is governed by births, deaths and migration
[Population Change] = [Births + Immigration] –[Deaths + Emigration]
Population Change = (B + I) – (D + E)
If the number of individuals added by births & immigration are balanced by those lost by deaths & emigration then there is zero population growth;

7. Population growth
Populations vary in their capacity for growth, also known as biotic potential
The intrinsic rate of increase (r) is the rate at which a population will grow if it had unlimited resources.

8. Population Growth
As long as there is a plentiful supply of resources populations grow
If we put some bacteria cells in a culture – the bacteria reproduce exponentially
As the population grows, so too does the rate of growth

9. Population Growth This is an example of positive feedback
The curve produced is sometimes called a J- curve
The J-curve assumes there is no limit on resources

10. Population Growth
Darwin calculate that if you started with 2 elephants and exponential growth, after 700 years the world population of elephants would be 19,000,000
This obviously has not happened

11. Population Growth
The size of a population is limited by available resources and competition for them
This results in a maximum size that an environment can sustain
The Carrying Capacity (K)

12. Population Growth
The carrying capacity is around 120 bacterial cells/mL
Negative feedback operates keeping the population around the Carrying Capacity

13. Population Growth This produces an S curve (logistic growth)
Limiting factors resulting from an increased population provide negative feedback which reduces the growth rate
Food, water, living space,
sunlight, etc

14. Population Growth
Lag phase: population grows slowly (environmental adaptation)
Exponential or Log phase: population grows rapidly exploiting a plentiful resource supply (maximal growth)
Stationary phase: population growth reaches a plateau – the maximum population size under the environmental conditions

15. Population Regulation
Factors that regulate population size can be categorized as DENSITY-INDEPENDENT or DENSITY-DEPENDENT
Density-Independent– effect does not vary with population density
Weather, climate, fire, volcano
Density-Dependent– effect varies with population density
infectious disease, competition, predation, waste accumulation, stress from crowding
Negative feedback that leads to stability of populations

16. Population Regulation
Factors that regulate population size can be categorized as INTERNAL or EXTERNAL
Internal factors – arise from within the population itself
fertility rates, breeding territory size, intraspecefic competition for food, genetic disease, competition for mates
External factors – affect populations from outside the population
predation pressure, parasitism, disease, climate change, interspecific competition

17. Exceeding the Carrying Capacity
Reindeer introduced to a small island off of Alaska in the early 1900s exceeded the carrying capacity, with an "overshoot" followed by a "population crash" in which the population was totally decimated by the mid–1900s.

18. Exceeding the Carrying Capacity
During the mid–1800s sheep populations exceeded the carrying capacity of the island of Tasmania. This "overshoot" was followed by a "population crash". Numbers then stabilized, with oscillation about the carrying capacity.

19. Population Curves in Nature
Population cycles for the snowshoe hare & Canadian lynx are believed to result because the hares periodically deplete their food, leading to first a crash of the hare population & then a crash of the lynx population.

20. Population Regulation
What regulates population?

21. Population Regulation
Until the 1940s, the British population of Peregrine falcons had remained fairly constant—about 820 breeding pairs
Limited by available nest sites (same places each year)
Average brood size was about 2.5 fledged young each summer
Come the next breeding season, the population was back to about 820 pairs
Equilibrium

22. Population regulation
Mosquitoes are plentiful in the summer months
When autumn sets in, the populations crash
Boom and bust

23. Population Regulation
Some species are very good at taking full advantage of any opportunity
Locust populations can explode
They swarm in the thousands, eat everything in their path, and eventually outstrip their food supply
Boom and bust

24. Population Regulation
The species described previously demonstrated either an equilibrium or boom and bust population growth
From this, two types of life strategies can be identified:
Equilibrium or K strategy species
Opportunist or r strategy species

25. Population Regulation
What are K and r?
The two variables that define a population curve
K = carrying capacity
r = growth rate (intrinsic rate of increase) r

26. K strategists Low reproductive rate Large investment in parental care
Late maturity
Slow growth
Large organisms
Late successional species
Niche specialists
Require stable environment
S—shaped curve
NC Zoo
Bomassa born 8/4 and Apollo born 8/31
Juma born 7/6

27. R strategists High reproductive rate Low investment in parental care
Early maturity
Rapid growth
Small organisms
Pioneer species
Generalists
Rapidly adapt to environmental variation
J—shaped curve

28. K and r strategists The reality is more of a continuum
Most organisms are located between the two extremes of this continuum and many show characteristics of both strategies

29. Survivorship
If survivorship is plotted for different species, three generalized types of life curve form
Type 1 (late loss) – Survivorship is high, most mortality later in life span
Type 2 (constant loss)– Constant mortality throughout life span
Type 3 (early loss)– High mortality early in life, low survivorship into late life span

31. Family Population Gather the following information:
Make a list of your living family members starting with your grandparents
Find out the year they were born and indicate if they are male or female
Include all of the brothers and sisters of your parents and everyone in your generation (brothers, sisters, cousins)

32. Bellwork
Tally your table’s totals for males and females at each age group
We will then combine the whole class data

33. Age Structure Diagrams
Show the proportion of the population at each age level
Three main age categories:
Prereproductive (ages 0-14)
Reproductive (15-44)
Postreproductive (45+)

34. Age Structure Diagrams

36. Edwards A1

37. Baby-Boom Generations
How can Age Structure Diagrams be used to make population and economic projections?
Baby-Boom Generations
Creates social and economic changes that ripple through a society for decades
Competition for jobs; political clout; retirement benefits and needs

38. What are the effects of population decline?
Rapid pop. decline can lead to severe economic and social problems
A sharp rise in proportion of elderly will lead to a large share of medical care, social security and other costly social services
Labor shortages

39. Human Population Dynamics
World Population (7 min)

40. Human Population History

41. Human Numbers Through Time
Click for interactive

42. Estimated Human Population Growth

43. Factors Affecting Human Population Size
Population change = [births + immigrations] – [deaths + emigration]
Zero Population Growth (ZPG) – when births plus immigration equal deaths plus emigration
Crude Birth or Death Rate - # births or deaths /1,000 people
U.S. CBR – 13.83
U.S. CDR – 8.38

44. World Population Rate of World's Population Change (%)
(Birth Rate – Death Rate)/1000 people x 100
Average Annual population growth rate
1.2% (global)
.963 (U.S.)
World Population = 7 billion (video)
China and India - 37% of world's population
U.S. – 4.5% of world's population
Population Clocks

45. World Population

46. Global Fertility Rates (2 types)
1. Replacement Level Fertility
number of children a couple must bear to replace themselves (2.1 in developed countries and 2.5 in developing countries)
greater than 2 because some female children die before reaching their reproductive years
Population Momentum – The continued growth of a population after reaching replacement level resulting from a large number of people entering their childbearing years

47. Global Fertility Rates (2 types)
2. Total Fertility Rate (TFR)
most useful for projecting future population change
the average number of children a woman will have during her childbearing years
2000
World – 2.9 (1.3 developed, 3.2 developing)
U.S. – 2.1
2011
World – 2.46
U.S. – 2.06

48. Global Fertility Rates

49. Total fertility rate (children born/woman)

50. U.S. Growth
US - highest fertility rate and highest immigration rate of any industrialized country – Why?
1.66 million more births than deaths; 800,000 legal immigrants; 300,000 illegal immigrants
***Because of the high per capita rate of resource use in the US, each addition to the US pop. has an enormous environmental impact!!

51. U.S. Growth Reasons for Projected Growth:
392 million by more than a 50 percent increase from the 1990 population size
Reasons for Projected Growth:
Large number of baby-boom women still in child-bearing years
Increase in number of unmarried mothers (incl. teenagers)
Continued higher fertility rates for women in some racial and ethnic groups than for Caucasian women
High levels of legal and illegal immigrants (43% of US pop. growth)
Inadequate family-planning services

52. What factors affect Birth and Fertility Rates?
Average level of education and affluence
Importance of children as part of the labor force
Urbanization
Cost of raising and educating children
Educational and employment opportunities for women
Infant mortality rate
Average age at marriage
Availability of private and public pension systems
Availability of legal abortions
Availability of reliable methods of birth control
Religious beliefs, traditions and cultural norms

53. What factors affect death rates?
Decline in the CDR (crude death rate) has led to the rapid incr. in world's pop. People started living longer!
“It's not that people stopped breeding like rabbits; it's just that they stopped dying like flies” (UN)

54. 2 Indicators of Overall Health
Life expectancy (the avg. number of years a newborn infant can expect to live)
75 years (developed countries)
64 years (developing countries)
U.S years (2011)
Angola – 38.76
What is your life expectancy?

55. 2 Indicators of Overall Health
2. Infant mortality rate - the number of babies out of every 1000 born each year that die within 1 year
The single most important measure of a society's quality of life –it reflects the general level of nutrition and health care

56. U.S. Infant Mortality Rate
deaths/1,000 live births
These rates are high because:
inadequate health care (poor women)
drug addiction (among pregnant women)
high birth rate among teenage women
Babies born to teenage women are more likely to have low birth weights – the most important factor in infant deaths
US – highest teenage pregnancy of any industrialized country

57. Should we reduce births?
Can we provide enough food, energy, water, sanitation, education, health care, and housing for twice as many people if the world pop. continues to grow?
Can we provide adequate standard of living for twice as many people without causing massive environmental damage?
Some say the Earth is already overpopulated
Others say the Earth could support billion people if everyone existed at a minimal survival level (grain diet only, cultivate all arable land, mine the Earth's crust to a depth of 1 mile)

58. Reducing Births Through Economic Development
Demographic Transition (a hypothesis of population change): As countries become more industrialized, first their death rates and then their birth rates decline
4 stages:

59. Demographic Transition
Pre-industrial stage – harsh living conditions, high IMR, DR, BR - growth is small

60. Demographic Transition
2. Transitional stage – industrialization begins, rise in food production, improved health care, lower DR, high BR, pop. grows rapidly (2.5-3%/year) – Developing countries

61. Demographic Transition
3. Industrial stage – industrialization is widespread. BR drops and approaches the DR. Better access to birth control, reduced IMR, incr. job opportunities for women, high cost of raising children, HS and college educations. Pop. grows but at a slower rate.

62. Demographic Transition
4. Post-industrial stage – BR declines further, equals (ZPG)
37 countries (mostly western Europe, 12% of world's pop.) are in this stage.

63. Ways to Reduce Births Family Planning Economic Rewards and Penalties
How many children and when to have them
Contraceptives (55% drop in TFR in developing countries)
Economic Rewards and Penalties
higher taxes, other fees, elimination of tax deductions for a third child, lose health care benefits, food allotments and job options
Work best if they encourage rather than mandate
Empowering Women
Education, jobs, rights

64. Hans Rosling : On Global Population Growth (10 minutes)

65. Limits to Growth How do we estimate carrying capacity for a species?
Examine requirements of given species
Examine resources available to given species
For Humans….
How deep is the barrel?

66. Limits to Growth Why is this difficult to estimate for humans?
Range of resources used is too great (MEDC vs LEDC)
Resource requirements vary according to lifestyles
Resource requirements differ from time to time and population to population
When a resource becomes limiting, we show great ingenuity in substituting one resource for another
Technological developments give rise to continual changes in the resources required and available for consumption

67. Limits to Growth Why is this difficult to estimate for humans?
3. Human populations regularly import resources from outside immediate environment
Enables them to grow beyond local boundaries
Increases their carrying capacity (but decreases it somewhere else!)

68. Limits to Growth
So what factors are used to determine human carrying capacity?
Rate of energy and material consumption
Level of pollution
Extent of human interference in global life-support systems
Affect reuse and recycling have on reducing these impacts/increasing carrying capacity

69. Population Practice Problems
The United States has a population of 3.15 billion and a growth rate of 0.9 percent. How long will it take our population to double?

70. Population Practice Problems
The United States has a CBR of 14 per 1,000 and a CDR of 8 per 1,000. What is the natural annual percent increase of our population?
Why is this different than the growth rate?

71. Population Practice Problems
Mexico has a population of 116,221 thousand. Last year, they experienced 2,163 thousand births, 574 thousand deaths, and -348 thousand net migrants. What was its net annual percentage growth rate?

72. Population Practice Problems
The current global human population is about 7 million and is growing at a rate of 1.2%. If the world population were to grow at this rate for the next year, approximately how many people would be added?