Population Change

Chapter 8 Population Change http://www.peterrussell.com/Odds/WorldClock.php

Do Now • What is Population Ecology? • What are some Principles of Population Ecology?

Principles of Population Ecology • Deals with the number of individuals of a particular species that are found in an area & how & why those numbers change over time. • Used in Forestry, agriculture, animal husbandry, and wildlife management.

Principles of Population Ecology • Population ecologists ask: • 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?

Principles of Population Ecology 20 / 25 m2 20 / 100 m2 • Population Density: • Not enough to know just how many. • Need to know per unit area.

Do Now: Principles of Population Ecology • How have immigration and emigration affected your local population? • HINT: consider impacts on education (K-postsecondary), housing, transportation, the workforce, social services, the local economy, and the local political climate,

Principles of Population Ecology • How Do Populations Change in Size? • On a global scale (closed system):

Principles of Population Ecology • How Do Populations Change in Size? • On a local scale (open system):

Principles of Population Ecology Death rate Growth rate Birth rate • How Do Populations Change in Size? • Global scale: r = b – d

Principles of Population Ecology Death rate Growth rate Emigration rate Birth rate Immigration rate • How Do Populations Change in Size? • Local scale: r = (b – d) + (i – e)

Hypothesize: : Your employer makes you this offer, Would you rather make: 0.01¢ a day that grows exponentially for 30 days $75 an hour working 30 days 8 hours a day?

Hypothesize: Your employer makes you this offer, Would you rather make: 0.01¢ a day that grows exponentially for 30 days $75 an hour working 30 days 8 hours a day? $75/hour x 8 hours= $600/day x 30days = $18,000/30days

Hypothesize: Your employer makes you this offer, Would you rather make: 0.01¢ a day that grows exponentially for 30 days Day $ 1. 0.01 2. 0.02 3. 0.04 4. 0.08 5. 0.16 6. 0.32 7. 0.64 8. 1.28 9. 2.56 10. 5.12 11. 10.24 12. 20.48 13. 40.96. 14. 81.92 15. 163.84 Day $ 27 671,088.64 1,342,177.28 2,684,354 $5,368,709.12

Principles of Population Ecology • Maximum Population Growth- • under ideal conditions = intrinsic rate of increase (aka biotic potential) J-shaped curve (exponential growth)

Do Now: Principles of Population Ecology • Explain why cockroach populations will not • expand indefinitely and take over the entire • world. • Include in your discussion appropriate • definitions of population growth terminology • such as: exponential growth, logistic • growth, carrying capacity, and resistant • factors.

Do Now: ANSWERSPrinciples of Population Ecology • Cockroaches populations exhibit exponential growth, that is accelerating population growth that occurs when optimal conditions allow a constant reproductive rate over a period of time. • When the cockroach population grows exponentially, the larger the population gets, the faster it grows (J curve). • However, environment resistance factors limit growth of the population. • These factors include such unfavorable environmental conditions as the limited availability of food, water, shelter, and other essential resources (resulting in increased competition) as well as limits imposed by disease and predation. • As the number of individuals in a population increases, so does environmental resistance, which acts to limit population growth. Because the environment sets limits, cockroach population growth is transformed from exponential growth into logistic growth. • In the logistic growth pattern, the population of roaches would level at the carrying capacity appropriate for the local environment. The carrying capacity is the maximum number of individual of a given species that a particular environment can support for an indefinite period, assuming thee are no changes in the environment.

Principles of Population Ecology • Environmental Resistance- • Exponential growth cannot occur forever. • The larger the population the faster it ____ ? • What factors prevent it from doing so? Grows S-shaped curve (logistic growth)

Principles of Population Ecology • Overshooting the carrying capacity can lead to a population crash.

Do Now: Reproductive Strategies • Please provide the 2 Life History Strategies. • List the their characteristics.

Do Now: Answers Reproductive Strategies K-selected vs. high growth rate slow growth rate small body size large body size early maturity late maturity short life span long life span large broods small broods little / no parental care high parental care • Life History Strategies r-selected

Reproductive Strategies • Survivorship

Do Now: Reproductive Strategies • Identify the two most extreme types of reproductive strategies and make a distinction between the traits that would characterize these extremes. • Give an example of an organism that illustrates each strategy.

Do Now: Answers Reproductive Strategies Populations described by r selection have traits that contribute to a high population growth rate. Weeds, such as dandelions, and insects, such as mosquitoes, are examples of “r” strategists. Distinguishing traits typical of r strategists include: small body size, early maturity, short life spans, large broods and little or no parental care of offspring. These organisms live in unpredictable environments where the probability of long-term survival is low. In populations described by K selection, traits maximize the chance of surviving in an environment where the number of individuals is near the carrying capacity of the environment. Characteristics of K strategists include: long life spans with slow development, delayed reproduction, large body size, and a low reproductive rate with high parental obligations to offspring. Tawny Owls, humans, elephants, and redwood trees are all examples of the “K” strategists.

Do Now: Principles of Population Ecology • Describe an example of a density- dependent and independent population factor.

Do Now: ANSWERPrinciples of Population Ecology • Describe an example of a density- dependent and independent population factor.

Factors that Affect Population Size • Density-Dependent Factors- • Factors that influence population growth when its density is high. • Predation, competition, disease.

Factors that Affect Population Size • Density-Independent Factors- • Regardless of population density, influences population growth. • Weather, fire.

Factors that Affect Population Size • Density-Dependence and Boom-or-Bust Population Cycles

Do Now: ANSWERS • Who was Thomas Malthus and what were his ideas about human population growth? Was he correct or not? Justify your answer.

Do Now: ANSWERS • Thomas Malthus was a 19th century British economist who was one of the first people to recognize that the human population cannot increase indefinitely. • He correctly pointed out human population growth is not always desirable because it can exceed the food supply resulting in famine, disease and war. Since Mathus’s time, the human population has increased from 1 to 6 billion. • Scientific advances have allowed food production to keep pace with population growth. Malthus may ultimately be correct in his ideas because we do not know if our increase in food production is sustainable.

Factors that Affect Population Size • Case-in-Point: Predatory Prey Dynamics on Isle Royale

Do Now: Factors that Affect Population Size • Discuss the factors that have regulated the moose population on Isle Royale. Your discussion should include the following terms: Predator-prey dynamics, density dependence, density independent factors.

Do Now: ANSWERFactors that Affect Population Size • On the island of Isle Royale, the moose population is preyed on by wolves. Prior to the introduction of predators on Isle Royale, the moose population was controlled by the supply of vegetation and viral diseases, which are both density dependent factors. • In addition, the density independent factor of severe winters killed the old and the young moose alike. When wolves were introduced, the predator – prey dynamics between the wolf and moose populations became the primary regulating factor of the moose population.

Factors that Affect Population Size • Case-in-Point: Predatory Prey Dynamics on Isle Royale

Factors that Affect Population Size East end of island West end of island

Factors that Affect Population Size example of small annual growth example of large annual growth

Factors that Affect Population Size

The Human Population • Human population size

The Human Population • Current Population Numbers • In 2004 = ~6.4 billion • Check out: • http://www.census.gov/main/www/popclock.html

Question about Human Population • The world population increased by 82 million from 2003-2004. Why has this occurred if the birth rate has declined during the past 200 years?

Question: ANSWER about Human Population • Due to advances in modern medical technologies; Vaccines, antibiotics, advances in medical facilities has led to a dramatic decrease in death rates.

The Human Population • Current Population Numbers • Rapid growth primarily due to drop in death rates

The Human Population • Projecting Future Population Numbers • When will zero population growth occur?

Do Now: Demographics of Countries • Describe at least three factors that determine whether a nation is classified as a developed or developing country?

Do Now: Answers Demographics of Countries • Describe at least three factors that determine whether a nation is classified as a developed or developing country? • life expectancy • health care system • educational system, esp. opportunities for women • amount of infrastructure • global vs local market economy • use of technology • degree of industrialization • standard of living • literacy rate • birth rate • death rate, esp. infant mortality rate • per capita GDP • degree of urbanization

Demographics of Countries • Most Populous Countries Insert Table 8.1

Demographics of Countries • Developed vs. Developing Countries Demographics Insert Table 8.2 (note reconstruction)

Population Change