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Chapter 5 Populations

Chapter 5 Populations. 5-1 How Populations Grow. I. Characteristics of Populations A. geographic distribution- or range describes the area inhabited by a population (ex. Few cubic centimeters of apple (bacteria) to millions of square kilometers of Pacific Ocean (whales)

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Chapter 5 Populations

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  1. Chapter 5Populations

  2. 5-1 How Populations Grow • I. Characteristics of Populations • A. geographic distribution- or range describes the area inhabited by a population (ex. Few cubic centimeters of apple (bacteria) to millions of square kilometers of Pacific Ocean (whales) • B. population density- number of individuals per unit area (ex. Tall saguaro cactuses and smaller desert plants)

  3. C. population growth- affected by number of births, deaths, and individuals entering and leaving population • immigration and emigration (ex. Otters/sea urchins/kelp/killer whales) • D. age structure- youth in a population is going to predict a more rapid growth (ex. US population vs. Rwanda population)

  4. II. Exponential growth • If a pop. has abundant space and food and is protected from predators and disease- the pop. size will increase indefinitely • Occurs when a population grows at a constant rate- starts slow then grows quickly • Called a J-shaped curve

  5. III. Logistic Growth • A. When resources become less available the growth slows or stops • B. The population reaches the carrying capacity which is the number of organisms that the particular environment can support • C. Called a S-shaped curve

  6. 5-2 Limits to Growth • Limiting factor- something that causes the population to decrease • I. Density-dependent limiting factors • A. Competition- when populations get crowded organisms compete for: • 1. food • 2. water • 3. space • 4. sunlight • 5. other essentials

  7. Density Dependent Limiting Factors • B. predation- ex. Chart of wolf and moose (p. 126) • C. parasitism and disease- like predators, parasites take nourishment often weakening and cause death (ex. Cordyceps fungus that infects insects)

  8. II. Density-independent limiting factors • A. Unusual weather- tornados, hurricanes • B. Natural disasters- fire, rain • C. Seasonal cycles- frost, drought • D. Human activities- damming rivers, clearing forest

  9. 5-3 Human Population Growth • Human Population- Dot Video

  10. A. The human population cannot keep growing forever because the earth and its resources are limited • B. Demography- study of human populations • 1. With advances in nutrition, sanitation and medicine more children survive and adults live longer • 2. As societies modernize, increase level of education, and raise their standard of living, families have fewer children

  11. 3. Demographic transition has occurred in the U.S., Europe, and Japan • 4. Much of today’s population occurs in 10 countries with India and China in the lead

  12. Chapter 6 (pg 152) Pollution • Biological magnification- concentrations of a harmful substance that increase in organisms at a higher trophic levels • DDT pesticide problem • Cheap, long activity, kills many types of insects, controls pests and mosquitoes • Hazardous: nonbiodegradable and organisms don’t eliminate it from their bodies • The pesticide remains in tissues of plants and passed to the herbivores and omnivores • Top predator fish-eating birds were affected the most, causing thin eggs shells and death of offspring and the threatening of their populations

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