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CH. 4 POPULATION ECOLOGY. CH. 4.1 – POPULATION DYNAMICS Main Idea – populations of species are described by density-spatial distribution, and growth rate. QUESTION: What are some observations you can make about populations of insects over the course of a year? - PowerPoint PPT Presentation



  • CH. 4.1 POPULATION DYNAMICSMain Idea populations of species are described by density-spatial distribution, and growth rate.

    QUESTION: What are some observations you can make about populations of insects over the course of a year?

    Do the insects die out completely in winter?

  • POPULATION CHARACTERISTICSAll species occur in groups called populations.Each population have similar characteristics such as:DensitySpatial distributionGrowth ratePopulations are classified according to the characteristics above

  • POPULATION DENSITYPopulation density is the number of organisms per unit area.Population density is figured out by using this formula:Pop. Density = # individuals unit areaEx: 100 cheetahs in our 400 acre park=1 cheetah per 4 acres

  • SPATIAL DISTRIBUTION Dispersion is the pattern of spacing of a population within an area.3 main types of dispersion are:UniformClumped groupsRandom

    One of the primary factors in the pattern of dispersion is the availability of resources like food.

  • POPULATION RANGESNo population, not even humans, occupies all habitats in the biosphere.Some species have a very limited range, other species can have a vast distributionEX: honeycreeper only on 1 Hawaiian island, peregrine falcon on every continent, except Antarctica.Organisms adapt to the biotic and abiotic factors in their environmentLimitations to expanding your range can depend on whether you can adapt to the abiotic conditions found in the expanded range.Includes temperature range, humidity level, sunlight, etc.Biotic factors like predation, competitors, parasites, can make survival in the new location difficult.

  • POPULATION-LIMITING FACTORSLimiting factors are biotic or abiotic factors that keep a population from continuing to increase indefinitely.Changing the limiting factors will either increase or decrease a population.

    QUESTION: Imagine you are at a birthday party. How many people could come before there was not enough cake for everyone?

  • DENSITY-INDEPENDENT FACTORSDensity-independent factors are any limiting factors in the environment that does not depend on the number of members in the population per unit area.Usually abiotic factors such as weather events, such as: drought, flooding, extreme heat or cold, tornadoes, and hurricanesHumans can also unintentionally create alterations of the landscapeDams (changes water flow & T)Introduce non-native speciesAir, land, & water pollutionReduces resources because some are now toxic

  • DENSITY-DEPENDENT FACTORSDensity-dependent factors is any factor in the environment that depends on the number of members in a population per unit area.Density-dependent factors are usually biotic factors such as:PredationEx: Wolf/moose studyDiseaseOutbreaks of disease increase as populations so up because you are closer togetherParasitesOccurs similar to the affects of a diseaseCompetition Higher the population the less resources there are to go around

  • POPULATION GROWTH RATEPopulation growth rate will explain how fast a population grows.Factors that affect growth can be number of births & deathsEmigration which is when an individual will move out of the populationImmigration is when individuals move into a population

  • EXPONENTIAL GROWTH MODELExponential growth occurs when there are no limits placed on the population by the environment.Such as food, water, shelter, matesPopulation will grow slowly at first and then increase rapidlyGraph will have a J-shaped appearance.Growth will only slow when resources become limited

  • LOGISTIC GROWTH MODELLogistic growth occurs when the populations growth slows or stops following exponential growth.Population has reached the carrying capacityDevelops an S-shaped curved graphLogistic growth happens when there are less births than deaths or more emigration than immigration.

  • CARRYING CAPACITYCarrying capacity is the maximum number of individuals in a species that an environment can support for the long term.Limited by available energy, water, oxygen, and nutrientsOnce a population exceeds the carrying capacity you see more deaths than births Carrying capacity explains why populations tend to stabilizeCarrying capacity

  • QUESTION?Discuss together and come up with answer to the following question. Be prepared to support your answer with information from the text:Hypothesize what might happen to a population that has reached its carrying capacity if a competing species emigrated from the environment.

  • SECTION 4.2 HUMAN POPULATIONMAIN IDEA Human population growth will change over time.

    Your perception of human population growth might be different if you lived in one of the worlds largest cities such as Mexico City with a population of 17 million or in a small town such as Dellview, North Carolina, with a population of 16.QUESTION: No matter where you live, would you say that the total population is growing faster today or that it grew faster 50 years ago?

  • HUMAN POPULATION GROWTHDemography is the study of human population size, density, distribution, movement and birth and death rates.Demographers keep track of the population size and have charted the size over millions of years.Population in 2012 is estimated to reach 7 billion peoplePopulation in 2050 is estimated to reach 9 billionFigure 11 on pg. 100, what type of graph is shown?

  • TECHNOLOGICAL ADVANCESFor a long time environmental conditions kept the size of the human population at a constant number below the carrying capacity.Now we alter the environment that has changed the carrying capacityAgricultureFarm animalsTechnological advances and medicine have improved the survival rate for humansImprovements in shelter makes humans now less vulnerable to climate impact

  • HUMAN POPULATION GROWTH RATEHuman population is still growing, but the rate of growth has slowedReason for the decline in the rate of growth in the US is AIDS and voluntary population control

  • TRENDS IN HUMAN POPULATION GROWTHPopulation trends can be altered by events such as disease and war.Historical events have changed populations trends, such as the industrial revolutionHuman population growth is not the same in all countriesBut you will see similar population growth trends in similar economiesDemographic transition is the change in a population from high birth and deaths to low birth and deathsDeveloping countries add more people to the world population vs. industrial countries, pg. 103, Table 1

  • ZERO POPULATION GROWTHZero population growth (ZPG) occurs when births plus immigration equals deaths plus emigration.Estimated that the world population will reach zero population growth between 2020 with 6.64 billion people and 2029 with 6.90 billion people.

  • AGE STRUCTUREPopulations age structure is the number of males and females in each of 3 age groups: Pre-reproductive stageBefore age 20Reproductive stageBetween the ages of 20 & 44Post reproductive stageAfter age 44Represented by an age structure diagramLooks different Depends on if the country is experiencing rapid growth or zero population growth


  • HUMAN CARRYING CAPACITYHuman population will reach or exceed carrying capacityAs population reaches carrying capacity, areas will be become overcrowded and disease and starvation will occur.Technology continues to increase the level of carrying capacityDepends on how much resources are used by each personIndustrialized countries use more resources than developing countriesAs developing countries become industrialized, more demand is put on resources