1 / 49

5-2 What Limits the Growth of Populations?

5-2 What Limits the Growth of Populations? . Concept 5-2 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources. . Most Populations Live Together in Clumps or Patches (1).

zulema
Download Presentation

5-2 What Limits the Growth of Populations?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 5-2 What Limits the Growth of Populations? • Concept 5-2 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

  2. Most Populations Live Together in Clumps or Patches (1) • Population: group of interbreeding individuals of the same species • Population distribution • Clumping • Uniform dispersion • Random dispersion

  3. Most Populations Live Together in Clumps or Patches (2) • Why clumping? • Species tend to cluster where resources are available • Groups have a better chance of finding clumped resources • Protects some animals from predators • Packs allow some to get prey

  4. Population of Snow Geese Fig. 5-11, p. 112

  5. Generalized Dispersion Patterns Fig. 5-12, p. 112

  6. Populations Can Grow, Shrink, or Remain Stable (1) • Population size governed by • Births • Deaths • Immigration • Emigration • Population change = (births + immigration) – (deaths + emigration)

  7. Populations Can Grow, Shrink, or Remain Stable (2) • Age structure • Pre-reproductive age • Reproductive age • Post-reproductive age

  8. Some Factors Can Limit Population Size • Range of tolerance • Variations in physical and chemical environment • Limiting factor principle • Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance • Precipitation • Nutrients • Sunlight, etc

  9. Trout Tolerance of Temperature Fig. 5-13, p. 113

  10. No Population Can Grow Indefinitely: J-Curves and S-Curves (1) • Size of populations controlled by limiting factors: • Light • Water • Space • Nutrients • Exposure to too many competitors, predators or infectious diseases

  11. No Population Can Grow Indefinitely: J-Curves and S-Curves (2) • Environmental resistance • All factors that act to limit the growth of a population • Carrying capacity (K) • Maximum population a given habitat can sustain

  12. No Population Can Grow Indefinitely: J-Curves and S-Curves (3) • Exponential growth • Starts slowly, then accelerates to carrying capacity when meets environmental resistance • Logistic growth • Decreased population growth rate as population size reaches carrying capacity

  13. Logistic Growth of Sheep in Tasmania Fig. 5-15, p. 115

  14. 2.0 Population overshoots carrying capacity Carrying capacity 1.5 Population recovers and stabilizes Population runs out of resources and crashes Number of sheep (millions) 1.0 Exponential growth .5 1800 1825 1850 1875 1900 1925 Year Fig. 5-15, p. 115

  15. 2.0 Population overshoots carrying capacity Carrying capacity 1.5 Population recovers and stabilizes Population runs out of resources and crashes Number of sheep (millions) 1.0 Exponential growth .5 1800 1825 1850 1875 1900 1925 Year Fig. 5-15, p. 115

  16. Science Focus: Why Do California’s Sea Otters Face an Uncertain Future? • Low biotic potential • Prey for orcas • Cat parasites • Thorny-headed worms • Toxic algae blooms • PCBs and other toxins • Oil spills

  17. Population Size of Southern Sea Otters Off the Coast of So. California (U.S.) Fig. 5-B, p. 114

  18. Case Study: Exploding White-Tailed Deer Population in the U.S. • 1900: deer habitat destruction and uncontrolled hunting • 1920s–1930s: laws to protect the deer • Current population explosion for deer • Spread Lyme disease • Deer-vehicle accidents • Eating garden plants and shrubs • Ways to control the deer population

  19. Mature Male White-Tailed Deer Fig. 5-16, p. 115

  20. When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash • A population exceeds the area’s carrying capacity • Reproductive time lag may lead to overshoot • Population crash • Damage may reduce area’s carrying capacity

  21. Exponential Growth, Overshoot, and Population Crash of a Reindeer Fig. 5-17, p. 116

  22. Population overshoots carrying capacity 2,000 1,500 Population crashes Number of reindeer 1,000 Carrying capacity 500 0 1910 1920 1930 1940 1950 Year Fig. 5-17, p. 116

  23. Species Have Different Reproductive Patterns (1) • Some species • Many, usually small, offspring • Little or no parental care • Massive deaths of offspring • Insects, bacteria, algae

  24. Species Have Different Reproductive Patterns (2) • Other species • Reproduce later in life • Small number of offspring with long life spans • Young offspring grow inside mother • Long time to maturity • Protected by parents, and potentially groups • Humans • Elephants

  25. Under Some Circumstances Population Density Affects Population Size • Density-dependent population controls • Predation • Parasitism • Infectious disease • Competition for resources

  26. Several Different Types of Population Change Occur in Nature • Stable • Irruptive • Population surge, followed by crash • Cyclic fluctuations, boom-and-bust cycles • Top-down population regulation • Bottom-up population regulation • Irregular

  27. Population Cycles for the Snowshoe Hare and Canada Lynx Fig. 5-18, p. 118

  28. 160 Hare Lynx 140 120 100 80 Population size (thousands) 60 40 20 0 1845 1855 1865 1875 1885 1895 1905 1915 1925 1935 Year Fig. 5-18, p. 118

  29. Humans Are Not Exempt from Nature’s Population Controls • Ireland • Potato crop in 1845 • Bubonic plague • Fourteenth century • AIDS • Global epidemic

  30. Chapter 6 The Human Population and Its Impact

  31. 6-1 How Many People Can the Earth Support? • Concept 6-1 We do not know how long we can continue increasing the earth’s carrying capacity for humans without seriously degrading the life-support system that keeps us and many other species alive.

  32. Core Case Study: Slowing Population Growth in China: A Success Story • 1.3 billion people • Promotes one-child families • Contraception, abortion, sterilization • Fast-growing economy • Serious resource and environmental problems

  33. Crowded Street in China Fig. 6-1, p. 125

  34. Human Population Growth Continues but It Is Unevenly Distributed (1) • Reasons for human population increase • Movement into new habitats and climate zones • Early and modern agriculture methods • Control of infectious diseases through • Sanitation systems • Antibiotics • Vaccines • Health care • Most population growth over last 100 years due to drop in death rates

  35. Human Population Growth Continues but It Is Unevenly Distributed (2) • Population growth in developing countries is increasing 9 times faster than developed countries • 2050 • 95% of growth in developing countries • 7.8-10.8 billion people • Should the optimum sustainable population be based on cultural carrying capacity?

  36. Human Population Growth Fig. 1-18, p. 21

  37. 2.5 2.0 1.5 Average annual global growth rate (percent) 1.0 0.5 0.0 1950 1970 1990 2010 2030 2050 Year Fig. 6-2, p. 127

  38. Population Time Line: 10,000 BC - 2042 Figure 3, Supplement 9

  39. Annual Growth Rate of World Population, 1950-2010 Fig. 6-2, p. 127

  40. Where Population Growth Occurred, 1950-2010 Fig. 6-3, p. 127

  41. 10 9 8 7 World population (in billions) 6 5 4 Population in less-developed countries 3 2 1 Population in more-developed countries 0 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 Year Fig. 6-3, p. 127

  42. Five Most Populous Countries, 2010 and 2050 Fig. 6-4, p. 127

  43. 2010 China 1.3 billion India 1.2 billion United States 310 million Indonesia 235 million Brazil 193 million 2050 India 1.7 billion China 1.4 billion United States 439 million Pakistan 335 million Indonesia 309 million Fig. 6-4, p. 127

  44. 11 UN high-fertility variant (2008 revision) U.S. Census Bureau (2008 update) UN medium-fertility variant (2008 revision) 10 IIASA (2007 update) UN low-fertility variant (2008 revision) 9 World population (in billions) 8 7 6 2010 2020 2030 2040 2050 Year Fig. 6-A, p. 128

  45. Science Focus: Projecting Population Change • Why range of 7.8-10.8 billion for 2050? • Demographers must: • Determine reliability of current estimates • Make assumptions about fertility trends • Deal with different databases and sets of assumptions

  46. World Population Projections to 2050 Fig. 6-A, p. 128

  47. Science Focus: How Long Can The Human Population Keep Growing? • Thomas Malthus and population growth: 1798 • Overpopulation and overconsumption • Will technology increase human carrying capacity? • Can the human population grow indefinitely?

  48. Natural Capital Degradation: Altering Nature to Meet Our Needs Fig. 6-B, p. 129

  49. Natural Capital Degradation Altering Nature to Meet Our Needs Reducing biodiversity Increasing use of net primary productivity Increasing genetic resistance in pest species and disease-causing bacteria Eliminating many natural predators Introducing harmful species into natural communities Using some renewable resources faster than they can be replenished Disrupting natural chemical cycling and energy flow Relying mostly on polluting and climate-changing fossil fuels Fig. 6-B, p. 129

More Related