3Population DynamicsStudying how populations change in size, density, age distribution, and population distribution.Size: number of individualsDensity: how many are in a certain areaAge distribution: proportion of each age groupPopulation distribution: how the organisms arrange themselves in their habitat
4Population Distribution Clumping: Most common. Safety in numbers, social interaction, mating and caring for young, resources are clumpedMostcommon.Uniform: Not as common. Used because of scarcity of resourcesRandom: Quite rare. Can be hard to determine between truly random or largely “clumpy”
5What goes up must come down Increases in population: through birth or immigrationDecreases in population: through death or emigration.Change in PopulationBirths + ImmigrationDeaths + EmigrationNote: You should know difference between Immigration & Emigration!
6Age StructureWhat is expected to happen if a large % of the population is under the age of 10?What is expected to happen if a large % of the population is over the age of 65?What is expected to happen if there is an equal distribution in age?Growth will remain stable, then increase in yearsGrowth will decreaseGrowth remain stable
7What stage are you?Prereproductive stage: Those not through puberty; reproductively immature.Reproductive stage: Those who are capable of reproductionPostreproductive stage: Organisms that are too old to reproduce.Note: while males are capable of reproduction longer, “survival of the fittest” can prevent them from breeding once they are too old.
8Old Bio Stuff Abiotic vs. Biotic Factors That limit population growth Living factorsReproduction ratesFood supplyHabitatResistance to diseaseAbility to adapt to changeNot livingSunlightTemperatureClimateChemical environment
9(environmental resistance) POPULATION SIZEGrowth factors(biotic potential)Favorable lightFavorable temperatureFavorable chemical environment(optimal level of critical nutrients)AbioticBioticHigh reproductive rateGeneralized nicheAdequate food supplySuitable habitatAbility to compete for resourcesAbility to hide from or defendagainst predatorsAbility to resist diseases and parasitesAbility to migrate and live in otherhabitatsAbility to adapt to environmentalchangeDecrease factors(environmental resistance)Too much or too little lightTemperature too high or too lowUnfavorable chemical environment(too much or too little of criticalnutrients)Low reproductive rateSpecialized nicheInadequate food supplyUnsuitable or destroyed habitatToo many competitorsInsufficient ability to hide from or defendInability to resist diseases and parasitesInability to migrate and live in otherInability to adapt to environmentalBiotic potential = growthEnvironmental resistance = decrease
10A population will increase if…. A) Natality decreasesB) Mortality increasesC) Biotic potential increasesD) The environmental resistance increases
11A population will increase if…. A) Natality decreasesB) Mortality increasesC) Biotic potential increasesD) The environmental resistance increases
12Any of these would take place for answer C. Favorable lightFavorable temperatureFavorable chemical environment(optimal level of critical nutrients)AbioticBioticHigh reproductive rateGeneralized nicheAdequate food supplySuitable habitatAbility to compete for resourcesAbility to hide from or defendagainst predatorsAbility to resist diseases and parasitesAbility to migrate and live in otherhabitatsAbility to adapt to environmentalchangeAny of these would take place for answer C.Biotic potential = growth
13Exponential or Logistic Growth Curve? “Boom and Bust”“Boom then stable”
14Environmental resistance Logistic GrowthWill see exponential growth at first introduction to new environment. Video to follow this lecture.Then, growth will be limited by environmental factors and will follow carrying capacityS shapedPopulation size (N)Time (t)Carrying capacity (K)Environmental resistanceBioticpotentialExponentialgrowth
16Going up…Intrinsic rate of increase (r) is the rate the population would grow if it had unlimited resources.Can be seen as the “boom” of the population.r species: reproduce early in life, reproduce often, have many offspring each time.
17Coming down…Overshoot occurs when the population “booms” and is too great for the resources to supportOvershoot is followed by dieback, or the sudden decrease in populationReproductive time lag: the amount of time it takes for the birth rate to fall and death rate to rise. If the time lag is too long, environmental damage can occur which further limits the carrying capacity.
24Population DensityDensity-dependent controls: Limits populations that are too high.Examples: competition for food, shelter, water; disease; parasites, predationDensity-independent controls: Decreases population regardless of size.Examples: weather, temperature, natural disasters, habitat destruction, chemical changes in the environment
25Who’s in control here? Top-down control: (Predator Controls Prey) Structure of lower trophic levels depends on effect of consumers at high trophic levels.Bottom-up control: (Prey Controls Predator)Structure depends on prey availability and nutrient content from low trophic levelsExample: Hare population is controlled either by the lynx killing it (top-down) or by large numbers of hare using up their food source (bottom-up)
26Let’s talk about sex…old bio stuff Asexual reproduction: does not require sperm/egg. Mitosis – cell splitting. Bacteria reproduce this way. Only 3% of all species use this formSexual reproduction: requires sperm/egg, but not necessarily intercourse/copulationDisadvantages:Males don’t give birthIncreased chance of genetic defect/errorCourtship and mating rituals can be complexAdvantages: (get your mind out of the gutter!)Genetic variety/diversityParents can divide responsibilities
27What species are you? Carrying capacity K species; experience Number of individualsTimeCarrying capacityK species;experienceK selectionr species;r selection
29Species r-selected Species K-selected Species Found at bottom of population curveReproduce early in lifeReproduce frequentlyLarge numbers of offspringLittle to no parental careBoom and bust populationsExamples:FrogsCockroachDandelionsMiceMost insectsFound at top of population curveReproduce later in lifeReproduce less frequentlyHave less offspring at one timeLower infant mortalityLogistic graph (stable at top)Examples:HumansElephantsWhalesLong-living plants (oaks, rain forest trees)
36R-selected Species or K-selected species? HINT: The Capybara is the largest rodent in the world
37Percentage surviving (log scale) Survivorship CurvesEarly loss: high infant mortality (fish, frogs)Constant loss: death rate even among all ages (song birds)Late loss: low infant mortality (humans, elephants)Percentage surviving (log scale)100101AgeEarly lossConstant lossLate loss
38Isolation isn’t best… Problems when small, isolated populations exist. Founder effect: small group is geographically isolated. May not have the genetic diversity to survive (coloring, fur cover, etc)Demographic bottleneck: only a few surviving individuals may not have the genetic diversity to rebuild the populationGenetic drift: some individuals breedmore and dominate the gene pool(wolves)Inbreeding: related individuals in anarea mate. Can increase geneticdefects.
40Oops! I did it again… Past mistakes that need to be stopped: Reducing biodiversity by destroying, fragmenting and degrading habitats
41Oops! I did it again… Past mistakes that need to be stopped: Reducing biodiversity by simplifying natural ecosystems (monocultures – one type)
42Oops! I did it again… Past mistakes that need to be stopped: Unintentional strengthening of pest species and anti-biotic resistant bacteria
43Oops! I did it again… Past mistakes that need to be stopped: Elimination of natural predators (wolves, cougars, buffalo, eagles)
44Oops! I did it again… Past mistakes that need to be stopped: Over-harvesting renewable resources
45Oops! I did it again… Past mistakes that need to be stopped: Interfering with natural cycles in natural
46Oops! I did it again… Past mistakes that need to be stopped: Over dependence on fossil fuels
474 Guidelines for a Sustainable Future Our lives and economies are dependant on the earth and sun. They don’t depend on us.Everything is interconnected.You can’t change only one thing in natureWe cannot sustain our civilization if we deplete the natural capital. We must live off the biological interest of that capital.
48Population Control Solar Energy Nutrient Recycling Biodiversity PRINCIPLESOFSUSTAINABILITYNutrientRecyclingBiodiversity