2 ObjectivesThe student will investigate and understand dynamic equilibrium within populations, communities, and ecosystems.Key concepts include:interactions within and among populations including carrying capacities, limiting factors, and growth curves;Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
3 Population DynamicsPopulation: all the individuals of a species that live together in an areaDemography: the statistical study of populations, make predictions about how a population will changeAlthough several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
4 3 Key Features of Populations SizeDensityDispersion(clumped, even/uniform, random)Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
5 3 Key Features of Populations 1. Size: number of individuals in an areaAlthough several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
6 3 Key Features of Populations Growth RateBirth Rate (natality) - Death Rate (mortality)How many individuals are born vs. how many dieBirth rate (b) − death rate (d) = rate of natural increase (r).Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
7 Factors That Affect Future Population Growth Immigration++-PopulationMortalityNatality-Emigration
8 Population Dynamics Addition of individuals to populations Removal of individuals from populations
9 3 Key Features of Populations 2. Density: measurement of population per unit area or unit volumeFormula: Dp= NPop. Density = # of individuals ÷ unit of spaceSAlthough several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
10 Factors that Affect Density Immigration- movement of individuals into a population Emigration- movement of individuals out of a population
11 Factors that Affect Density Density-dependent factors- Biotic factors in the environment that have an increasing effect as population size increases Ex. diseasecompetitionparasites
12 Humans Are Not Exempt from Nature’s Population Controls IrelandPotato crop in 1845Bubonic plagueFourteenth centuryAIDSGlobal epidemic
13 Factors that Affect Density Density-independent factors- Abiotic factors in the environment that affect populations regardless of their density Ex. temperaturestormshabitat destructiondrought
14 Density-Independent Factors (e.g., weather) Good Times!(in Australia)
15 3 Key Features Populations 3. Dispersion: describes their spacing relative to each otherclumpedeven or uniformrandomAlthough several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
16 clumped even (uniform) random Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.random
17 Clumped Dispersion of Population Clumped dispersion implies some sort of cohesive force, e.g., either individuals seek other individuals out, or individuals are limited in where then can reside
18 Uniform Dispersion of Population Uniform dispersion implies some sort of antagonistic interaction, e.g., either individuals actively repel other individuals
19 Random Dispersion of Population Random dispersion implies a minimum of interspecific interactions that impact where individuals reside
20 Other Factors That Affect Population Growth Limiting factor- any biotic or abiotic factor that restricts the existence of organisms in a specific environment.EX.- Amount of waterAmount of foodTemperature
21 Limiting Factor- Zone of Tolerance Few organisms presentNoneFew organisms presentNoneMany organisms presentAlthough several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
22 Other Factors that Affect Population Growth Carrying Capacity- the maximum population size that can be supported by the available resourcesThere can only be as many organisms as the environmental resources can supportAlthough several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
23 No Population Can Continue to Increase in Size Indefinitely Biotic Potential = Intrinsic growth rate: Maximum potential for growth –occurs where there is unlimited resources
24 Logistic Growth of a Sheep Population on the Island of Tasmania, 1800–1925 Oscillations about K (the carrying capacity)_
25 Exponential Growth, Overshoot, and Population Crash of a Reindeer Irruptive Population Curve
26 Population Cycles for the Snowshoe Hare and Canada Lynx Boom and Bust Population Curve
27 2 Life History Patterns r Strategists short life span small body size reproduce quicklyhave many younglittle parental careEx: cockroaches, weeds, bacteria
28 2 Life History Patterns K Strategists long life span large body size reproduce slowlyhave few youngprovides parental careEx: humans, elephants
40 Growth RateWhat is the formula for finding natural increase (growth rate)?r = b – dr = 26/ /1000r = – = 0.0210.021 X 100 = 2.1% per yearOR (the easy way)r = 26/10 - 5/10r = = 2.1or 2.1% per year
41 Doubling TimeRule of 70 – determines the number of years it will take a country’s population to double.Doubling time = 70/%growth rateGrowth rate = 70/doubling timeLet’s practice:A country’s growth rate is 1.5%. How many years will it take that country’s population to double?70/1.5 = 46.7 years
42 How do population pyramids help us learn about population?
44 Population in millions Population pyramids are used to show information about the age and gender of people in a specific country.MaleFemaleThere is also a high Death Rate.In this country there is a high Birth RatePopulation in millionsThis population pyramid is typical of countries in poorer parts of the world (LEDCs.)
45 In some LEDCs the government is encouraging couples to have smaller families. This means the birth rate has fallen.
46 Population in millions MaleFemalePopulation in millionsThe largest category of people were born about 40 years ago.In this country the number of people in each age group is about the same.In this country there is a low Birth Rate and a low Death Rate.This population pyramid is typical of countries in the richer parts of the world (MEDCs.)
47 Population in millions MaleFemalePopulation in millionsIn the future the elderly people will make up the largest section of the population in this country.In this country the birth rate is decreasing.This is happening more and more in many of the world’s richer countries.
48 Population in thousands MaleFemalePopulation in thousandsThis country has a large number of temporary workers. These are people who migrate here especially to find a job.
49 Population pyramid for Mozambique. Population pyramid for Iceland.
59 What is the Demographic Transition? The shift from high to low mortality and fertilityA sign of socio-economic progress?TimeNaturalincreaseBirth rateDeath rateNote: Natural increase is produced from the excess of births over deaths.The shift from high mortality and fertility to low mortality and fertility is known as the “demographic transition.”It is based on the experience of Western Europe, in particular England and Wales.This model was first described by the American demographer Warren Thompson in 1929.In 1945, Frank W. Notestein further developed this theory and suggested that there was a relationship between population change and industrialization. A debate continues questioning if population growth must decline for economic development or if economic progress (or industrialization) leads to slower population growth.In light of this debate, the completion of the demographic transition has come to be associated with socioeconomic progress.[FYI – The factors that drive childbearing trends—such as the economy, education, gender relations, and access to family planning—are numerous and complex. These same factors are signs of socioeconomic development.]
60 Demographic Transition Read pagesWhat is the definition of demographic transition?Identify the characteristics of each stage.Stage DescriptionFirst Stage – Pre IndustrialSecond Stage -- TransitionalThird Stage -- IndustrialFourth Stage – Post Industrial
61 Demographic Transition in Sweden and Mexico Sources: B.R. Mitchell, European Historical Statistics (1976): table B6; Council of Europe, Recent Demographic Developments in Europe 2001 (2001): tables T3.1 and T4.1; CELADE, Boletin demografico 69 (2002): tables 4 and 7; Francisco Alba-Hernandez, La poblacion de Mexico (1976): 14; and UN Population Division, World Population Prospects: The 2002 Revision (2003): 326.Births/Deaths per 1,0001750Compare the transitions between these two countries to the classic model.Why are the two countries so different?[A: The short answer is that Sweden’s transition occurred gradually over 150 years. Mexico experienced rapid declines in death rates due to rapid implementation of better health care and sanitation technologies. The result was that Mexico’s population boomed during this period. It took time for the decline in birth rates to catch up. At the same time, this boom created its own momentum as all these new families have children of their own. Eventually Mexico’s population will likely stabilize (or even shrink), but at a much greater overall population. This pattern was repeated in many nations in the 20th Century, fueling a global population explosion. However, we’re also seeing in several countries – including Sweden – birth rates have dropped below death rates leading to population decline in most of Europe, Japan, and some other nations.]