1. Go to Section: 5–1How Populations Grow A. Characteristics of Populations B. Population Growth C. Exponential Growth D. Logistic Growth Section 5-1 Section Outline

2. Go to Section: 5-1 How Populations Grow Population - group of organisms belonging to a single species that lives in a given area. 3 Characteristics of any Population 1.Geographic distribution – area inhabited by population 2.Density - # per unit of space 3.Growth rate – how fast it grows

3. Go to Section: Population Growth Four factors that influence population size 1.Birth – duh. 2.Mortality - death 3.Emigration – out of an area 4.Immigration – into an area When these factors are balanced = no growth (negative or positive) What factors would increase size? Decrease size?

4. Go to Section: What environmental factors influence these? Birth and immigration? –Abundance of resources (food, mates, shelter) –Organisms reproduce and move into the area for the resources Mortality and emigration? –Resources on the decline –Organisms faced with dilemmas Adapt to other resources Death/extinction Move out - emigrate

5. Go to Section: Exponential Growth Bacteria reproduce on average every 20 minutes In a matter of 1day, one bacteria reproduce into…. –4720000000000000000000 bacteria –mass of bacteria size of earth in 3 days Represented with a “J-curve © ” Only occurs under ideal conditions (unlimited resources/no predation)

6. Go to Section: Exponential Growth Chart

7. Go to Section: Logistic Growth Normal growth curves Populations that grow exponentially use resources exponentially! –“carrying capacity” –The limit to which any population ceases to grow due to depletion of resources Run out of food Nowhere to live

8. Go to Section: Number of Yeast Cells Time (hours) Carrying capacity Section 5-1 Figure 5-4 Logistic Growth of Yeast Population

9. Go to Section: Population Growth can be represented bycharacterized by represented by which cause a Exponential growth Logistic growth Falling growth rate S-shaped curve Limits on growth No limits on growth J-shaped curve Constant growth rate Unlimited resources Section 5-1 Concept Map

10. Go to Section: Name That Resource! A situation that causes the growth of a population to decrease is called a limiting factor. Some limiting factors depend on the size of the population. Other limiting factors affect all populations in similar ways, regardless of the population size. Section 5-2 Interest Grabber

11. Go to Section: 1.Imagine a small island that has a population of five rabbits. How might each of the following factors affect the rabbit population? a. climate b. food supply c. predation 2.Now imagine another small island that has a population of 500 rabbits. How would the same factors affect this population? 3Which of the factors depend on population size? Which factors do not depend on population size? Section 5-2 Interest Grabber continued

12. Go to Section: 5–2Limits to Growth A.Limiting Factors B.Density-Dependent Factors 1.Competition 2.Predation 3.Parasitism and Disease C. Density-Independent Factors Section 5-2 Section Outline

13. Go to Section: Limiting Factors Factors that influence negative population growth can be anything from…. –Climate –Predators –Food availability –Parasites –Human influences Clearing of forests – destroy natural habitat

14. Go to Section: Density-Dependent Factors Any factor that is influenced by the density of the population. Competition –When populations become crowded, resources are used up at a faster rate. –Occurs within species as well as among groups of species. –Species that compete will change to ease the competition –Drives evolution Ex: plants and sunlight (canopies/black walnut)

15. Go to Section: Growth of Aphids Exponential growth Steady population size Peak population size Rapid decline Steady population size Section 5-2 A Density-Dependent Limiting Factor

16. Go to Section: Predation –Predator-prey relationship – regulation of populations by predators –Most effective population control “technique” –Ex: wolves and moose in Isle Royale –Graph usually fluctuates often over time Predator and prey charts are inverse of each other 60 50 40 30 20 10 0 195519601965197019751980198519901995 2000 1600 1200 800 400 0 2400 MooseWolves

17. Go to Section: Parasitism and Disease Disease and parasites very effective –Ability to spread directly related to density of population Higher density = faster spread = higher death rate –May be what eventually causes human population decline Ex: Bubonic plague

18. Go to Section: Density – Independent Factors Factors not caused by population size –Climatic change –Human disturbances Damming rivers, clearing forests Most populations will shrink in response –Unless these events are recurring or large in magnitude

19. Go to Section: How Fast Are We Growing? Until about 500 years ago, the world’s human population remained fairly stable. Then, as advances in medicine, agriculture, and technology occurred, the human population began growing very rapidly. Today, the world’s human population is greater than 6 billion people, and it continues to grow, but at a slower rate. Section 5-3 Interest Grabber

20. Go to Section: 1.The human population is increasing by about 1.4 percent each year. Assume that the population is 6 billion (6,000,000,000). How large will the population be in one year? 2.If the human population continues to grow at a rate of 1.4 percent per year, the population would double in size (to 12 billion people) in only 51 years! What effect might this increase in population have on the environment and on other people? Section 5-3 Interest Grabber continued

21. Go to Section: 5–3Human Population Growth A.Historical Overview B.Patterns of Population Growth 1.The Demographic Transition 2.Age Structure C.Future Population Growth Section 5-3 Section Outline

22. Go to Section: Historical Overview Populations of humans were regulated by the same limiting factors influencing other animals. –Harsh climate –Food supply –Predators 50% infant mortality rate as soon as 500 years ago. 8500 years ago – agriculture –Now instead of nomads, humans domesticated in one area –Increased the food supply –Coupled with high birth rate already, population increased

23. Go to Section: Agriculture begins Plowing and irrigation Bubonic plague Industrial Revolution begins Section 5-3 Human Population Growth

24. Go to Section: Patterns of Population Growth Human populations will cease to grow exponentially because of lack of resources. Today’s limiting factors: –Disease –Famine –War Demography – study of human populations Examine: –Birth rates –Death rates –Age structure Can predict future trends in growth or decline of population

25. Go to Section: Demographic Transition When the demography shifts in a population –Go from high birth rate/high death rate to…. –Low birth rate/low death rate How does a society do that? Occurred in the United States, Japan, and Europe Africa, S. America, and Asia, still have exponential growth….world overall still growing exponentially.

26. Go to Section: United States Demographic Transition

27. Go to Section: U.S. PopulationRwandan Population Males Females Section 5-3 Figure 5-13 Age Distribution

28. Go to Section:

30. What Can Age Structure Diagrams Tell Us? Trends by…. –Age group –Gender –Birth rate –Life Expectancy Overall quality of life

31. Go to Section: Future Population Growth By 2050 population may increase to 9 billion Growth rate will slow to 0.43% from 1.4% currently and 2.1% in the ’60’s. Some feel this is very bad for the environment Others feel technology and changes in society will allow us to cope.

32. Go to Section: Internet Links from the authors on the gray wolf Interactive test For links on populations, go to www.SciLinks.org and enter the Web Code as follows: cbn-2051.www.SciLinks.org For links on population growth, go to www.SciLinks.org and enter the Web Code as follows: cbn-2053.www.SciLinks.org Go Online