Presentation on theme: "1. Which of the following statements about conventional life tables is NOT true? They were first used by life insurance companies to estimate human survival."— Presentation transcript:
1 1. Which of the following statements about conventional life tables is NOT true? They were first used by life insurance companies to estimate human survival patternsThey show the age-specific death rates for a populationThey are used to predict population growthThey can be used to construct survivorship curvesThey are often constructed by following a cohort from birth to death.
2 2. To measure the population density of monarch butterflies occupying a park, 100 butterflies are captured, marked with a small dot on a wing, and then released. The next day, another 100 butterflies are captured, including the recapture of 20 marked butterflies. One would correctly estimate the population to be200050001000200500
3 - POPULATION GROWTH To predict how populations will increase or decrease,need a mathematical model.+births-DENSITYdeaths
4 Models of Population Growth: 1) Exponential Growth Model- assumes continuous breedingassumes during each and every time intervalthere is a possibility of births and deaths
5 Exponential Growth Model Change in population size (N) during a fixed time interval (t):N/ t = (b - d)Nb = births, d = deaths, N = current population size(b – d) = rr = the “intrinsic rate of natural increase” or the “per capita rate of increase”
6 Exponential Growth Model dN/dt = rmaxNrmaxN allows us to calculate the number of newindividuals added to a population in each generation:if rmax > 0, the population is growingif rmax < 0, the population is decliningif rmax = 0, the population is stable
7 Exponential Growth Example Ifb = 30/1000 = .03d = 10/1000 = .01rmax = b – d=rmax = .02N = 10,000ThendN/dt = rmaxN = .02(10,000) = 200 new individualsN2 = 10,200if we do this again, N3 = 10, new, etc.
16 The exponential growth model describes the increase in population size of a population that is not constrained by resources or space. The graph shows the elephant population in Kruger National Park, which appears to have been reproducing exponentially from 1900 to From this graph, you can tell thatA) none of the elephants died.B) a female elephant living around was more likely to have a baby than a female elephant living around 1920.C) the elephants adapted to the new park conditions around 1955.D) the vegetation the elephants eat could support more than 5,000 elephants.E) the more elephants there are, the more tourists will visit the park.Answer: d
18 When will we reach our carrying capacity and what factors will limit our growth?
19 Estimates of world carrying capacity range from 10-15 billion, though very difficult to estimate.One recent technique: “Ecological footprint”compares supply vs demand forecologically productive areas
20 Ecological FootprintEcological footprint measures the amount of arable land, pasture, forest, ocean, built-up land, and fossil energy land needed to support one person
21 Most ecologists agree that people should not be using more than 1 Most ecologists agree that people should not be using more than 1.7 ha of resources if they want to be sustainable. People in the United States use an average of 10 ha. This implies thatA) the ecological footprint concept is flawed.B) the U.S. has more land than other countries do.C) U.S. rates of resource consumption are too high.D) U.S. people are happier.E) U.S. people are less likely to emigrate.Answer: c
22 Ecological Footprint Relative to Ecological Capacity 161412108642New ZealandAustraliaCanadaSwedenWorldChinaIndiaAvailable ecological capacity (ha per person)SpainUKJapanGermanyNetherlandsNorwayUSAEcological footprint (ha per person)U.S. is in ecological deficit – we have an ecological footprint of 8.4 ha / person (it takes 8.4 ha to support us) but we have only 6.2 ha per personCountries in red are in ecological deficit;Countries in black still have resource surpluses