Chapter 5 Populations

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)

5. 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

6. 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

7. 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

8. 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)

9. 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

10. 5-3 Human Population Growth • Human Population- Dot Video

11. 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

12. 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

13. 6-1 A Changing Landscape • Human Influences • Hunting and gathering, agriculture, industry and urban development have all affected the natural activities of ecosystems around the world • Agriculture • The practice of farming and raising domesticated animals for food • Monoculture- growing the same crop on a large plot year after year • Green Revolution- the effort to develop larger quantities and better quality crops to feed growing population

14. Industrial Growth and Urban Development • Industrial Revolution in the 1800s- machines and factories led to the modern life we know • Many of our activities now need energy to power our machines which uses fossil fuels- coal, oil, and natural gas

15. 6-2 Renewable and Nonrenewable Resources • Tragedy of the Commons • I. Classifying Resources • Renewable Resources- can be regenerated or replenished by natural cycles- • These can still be overused and become limited • Ex. Trees, fish, water, soil • Nonrenewable Resources- cannot be regenerated and once used are gone forever • Ex. Coal, oil and natural gas

16. II. Sustainable Development • A way of using natural resources without depleting them or causing long term environmental harm • Takes into consideration how the natural ecosystem functions as well as how the human economic system operates

17. Resources JIGSAW! Split into groups and each group teaches about their resources! • III. Land • IV. Forest • V. Fishery • VI. Air • VII. Freshwater

18. 6-3 Biodiversity • One of Earth’s greatest natural resources • Many different species have provided us with food, industrial products, and medicines such as antibiotics, painkillers, heart drugs, antidepressants, and anticancer drugs. • Threats to biodiversity: • Altering habitats • Hunting species to extinction • Introducing toxic compounds into food webs • Introducing foreign species to new environments

19. 6.4 The Future • Ozone layer-limits our exposure to damaging UV rays from the sun, which can cause cancer, damage eyes, and decrease resistance to disease. • In 1974 it was shown that chlorofluoro-carbons, or CFCs, could damage the ozone layer. • CFCs were banned for use as propellants in aerosol cans, and the levels of chlorine in the atmosphere are falling.

20. Global climate change is a concern: • Global warming is the increase in the Earth’s average temperature range. 1998 was the warmest year since record-keeping began. • Is global warming a result of a larger, natural cycle or human actions? • Carbon dioxide levels have risen for the past 200 years, so the natural greenhouse effect has been intensified. • Recent models suggest that by 2050 the average global surface temperature will increase by 1 to 2 degrees Celsius.

21. Possible Effects of global warming: • 1. flooding of coastal areas • 2. some areas will see more droughts • 3. new organisms may live in areas where they once could not, or some may not be able to live where they once did.