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Population

Population. Chapter 8. Principles of Population Ecology. Population Ecology= the number of individuals of a particular species that are found in an area and how and why those numbers change over time. 1) How many are in the population? 2) Are its numbers increasing / decreasing?

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Population

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  1. Population Chapter 8

  2. Principles of Population Ecology • Population Ecology= the number of individuals of a particular species that are found in an area and how and why those numbers change over time. • 1) How many are in the population? • 2) Are its numbers increasing / decreasing? • 3) What is its pattern of reproduction? • 4) What is its pattern of mortality?

  3. Characteristics of a Population • Size • Number of individuals in the population at a given time. • Changes in response to changes in the environment. • Density • Number of individual’s/area • Varies with resources, habitat, climate, interaction with other species. • Age Structure • Percentage of each age group in a population. • Pre-reproductive, reproductive, and post-reproductive

  4. 20 / 25 m2 20 / 100 m2 Density • Not enough to know just how many. • Need to know per unit area.

  5. How Do Populations Change in Size? • On a global scale (closed system):

  6. How Do Populations Change in Size? On a local scale (open system):

  7. How do Populations Change in Size? • Global scale: Death rate Growth rate r = b – d Birth rate

  8. Rather than use total births and deaths (big #s!) calculations are done with : • Crude birth rate=# of births/1000 people • Crude death rate= # of deaths/1000 people

  9. Annual Growth Rate: AGRPopulation on a local scale r = (b – d) + (i – e) Emigration rate Growth rate Death rate Birth rate Immigration rate

  10. Annual Growth Rate (ARG) • % = (birth rate-death rate) x 100 • 1000 • Or ARG% = (birth rate-death rate) • 10

  11. Doubling time formula • DT=70/AGR% • Rule of 70% • A country will double its population • 70/2%= 35 A country with a 2% AGR will double its population in 35 years. • 70/.05%=140 years

  12. Example • Mayville Island is a paradise with few men and many fine women. Needless to say, the birthrate is VERY high. However, because the primary source of nutrition is soda, the death rate is also relatively high. Determine Crude birth rate (CBR), Crude death Rate (CDR), AGR, and Doubling time (DT). • Total Population 2005: 20,000 • Total Births 2005: 300 • Total Deaths 2005: 150

  13. Maximum Population Growth Without the influence of biotic and abiotic….all populations= J curve or exponential growth.

  14. Carrying Capacity (K) • How many organisms the land can support • Limit to the number of organisms that can live in an environment caused by abiotic and biotic limiting factors • Abiotic=light, temp, nutrients, weather • Biotic=reproductive rate, food/prey, hide/defend, disease resitant, adaptable • Limiting factors stop J curves • Populations fluctuate around carrying capacity and form S-curves (logistic growth)

  15. S-curve

  16. Crash-overshooting carrying capacity

  17. Reproductive Strategies R-Strategists K-Strategists • Many small offspring • Little prenatal care • Early reproductive age • Small adults • Adapted to unstable environments • High population growth rate (R) • Population size fluctuates wildly! Above and below carrying capacity (K) • Low ability to compete • Fewer, larger offspring • High prenatal care • Late reproductive age • Most live to reproductive age • larger adults • Adapted to stable climate • Lower population growth rate (R) • Population size is stable and close to carrying capacity (K) • High ability to cope

  18. Survivorship • Type 1: • The young do not easily die, most deaths occur at old age (k-strategists) • Type II: • Rare, death happens equally at all ages • Type III: • Common, most die at a young age. The lucky survive (r-strategists)

  19. Density Affects on Population • There are some environmental events that affect population the same regardless of density= Density independent (ex; earthquakes, fires, drought, etc.) • Some environmental events affect populations MORE if the population is dense= density dependent population control (competetion for resources, predation, disease)

  20. Density-Dependence and Boom-or-Bust Population Cycles

  21. Predator Prey Relationships

  22. Human Population http://ngm.nationalgeographic.com/7-billion?fs=traveler.nationalgeographic.com http://www.census.gov/main/www/popclock.html

  23. Case in Point • The African Problem • Most rapidly growing population on Earth, however, during the 1990’s many expects lowered growth due to the AIDS epedemic. • The birth rate is very high, but death rate is very high too. Life expectanct in Botswana was 60 in the 1980’s, it was 39 in 2002 • 7.5/10 people with AIDS live in sub-Saharan Africa. #1 cause of death • Cannot afford medicine, promiscuity, lack of education and protection

  24. Current Population NumbersRapid growth due to drop in death rate

  25. Most Populated Countries

  26. Fertility Rates • Replacement Fertility • Have kids to replace parents (2.1) • Total Fertility Rate (TFR) • Average # of children each woman has • 1.6 in developed countries • 3.3 in developing • 5.6 in Africa • World 2.8 • All higher in the 1950’s. Why?

  27. Factors that affect birth & fertility rates • Education & $$$ • Importance of children in labor force • Cost of raising & educating children • Average age of marriage • Availability of Birth Control

  28. US • Avg. Income $48,000 / family • Living in poverty 10% ( 7.7 million ) • Homeownership 66% • High School Diploma 80% • College Degrees 24% • Uninsured 11%

  29. China • Fast Facts • Population1,303,701,000 • CapitalBeijing; 10,849,000 • Area9,596,960 square kilometers(3,705,405 square miles) • LanguageChinese (Mandarin), Cantonese, other dialects and minority languages • ReligionTaoist, Buddhist, Muslim • Currencyyuan, also referred to as the Renminbi • Life Expectancy71 • GDP per CapitaU.S. $4,700 • Literacy Percent86

  30. http://www.youtube.com/watch?v=FDmPcSWE0WU

  31. U.S. has highest teenage pregnancy rate of developed nations. Why? • Does religious beliefs about contraception play a role in population?

  32. Demographic stages

  33. Demographics=deals with population statistics • Preindustrial Stage: Birth Rate and Death rate are high (many children, but many deaths due to poor medicine)= population grows slow! • Transitional Stage: Birth rate high and death rate is lower (more reliable food and water)= population booms • Industrial Stage: Birth Rate is lower and death rate is lower (less agriculture means less need for children, some birth control)= population grows slow • Post-industrial Stage: Birth rate and death rate are low (better education. Money, changing role of women)= population is stable or very slow growth.

  34. Age Structure

  35. Immigration and Nationality Act • Passed in 1952, now called “Immigration Reform and Control Act” (IRCA) • Abolished national quotas • Gave priority to : those with family members in U.S., those who can fill vacant jobs, and refugees seeking asylum • The U.S. legally accepts about 1 million immigrants per year • Estimate another 300,000 illegal immigrants enter each year.

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