What is Ecology?Ecology is the study of interactions between organisms and their environments. It can be studied at many levels including:IndividualsIndividual organismsPopulationsGroups of individual organism that interbreed with each otherCommunitiesPopulations of different species that interact with each other within a localeEcosystemsAll living organisms, as well as non-living elements, that interact in a particular areaIn your own neighborhood, which list below defines a biological community?The animals (including humans) as well as the plants living in your neighborhood.Population ecology is the study of how populations interact with their environments.Take home message:Mot ecological processes cannot be observed or studied within an individualRather, when studying them it is necessary to consider the entire group of individuals that regularly exchange genes in a particular localePopulation ecology examines features that cannot be studied on an individual organism, such as population size.Exponential GrowthOccurs when each individual produces more than single offspring necessary to replace itself.According to realistic (and moderate) estimates of birth and birth rates, a population of just 500 elk would grow to more than billion individuals within 80 years and eventually would cover the earth.Big Idea:Exponential growth is not really possible for long since a populations growth is limited by the environment (page 323)Density dependent factorsThe limitations on a populations growth that are a consequence of population densityThis ceiling on growth is the carrying capacity of the environment (page 322)Density dependent factors limit population sizeFood supplyHabitat for living and breedingParasite and disease riskPredation riskRealistically, biotic and abiotic factors in the environment limit the growth of a population.These limiting factors include:TemperatureWaterEnergy/ nutrient availabilityHuman Population: How high can it go??Very difficult to assess just how many resources each person needsEcological footprintsEvaluating how much land, how much food and water, and how much fuel, among other things, are necessary.Poverty in IndiaToo many people/ habitat overuse/ unequal distribution of resourcesResult: Environmental destruction and irreversible changes to ecosystems.Take home message:The world population is currently growing at a very high rate, but limited resources will eventually limit it, most likely at a population size between 7 and 11 billionHow many people can earth support?Why does the answer keep increasing?Development of agricultural technologies is one example of how carrying capacity can be increased.As we increase the carrying capacity of humans, we are decreasing the carrying capacity of other organismsFocus questionsHow has the earth’s changing environments/ climate impacted the human speciesGenographic project and human migrationsHow has human population impacted the ecology of the earth?Population size is also influenced by the way in which each type of organism lives: called Life HistoryThe vital statistics o the species — this includes the rate of population increase.Includes: age at first reproduction, probabilities of survival and reproduction at each age, litter size and frequency, and longevity.Variations in life histories:Big Bang reproductionReaches sexual maturity at one yearMates intensely over a three week periodMales die shortly after mating periodFast, intensive reproductive investmentReaches sexual maturity at one monthProduces litters of six to ten offspring every month.Slow, Gradual reproductive investmentReaches sexual maturity at one yearProduces about one offspring per year.Why all the variation?Is one strategy better than others for the survival of a species?There are many possible responses to the challenge of:When to reproduce,How often to reproduceHow much to reproduce.Life history tradeoffsReproduction and survivalBig bang reproducers such as salmon make a single exceptionally high investment in reproduction, then die shortly after.Survivorship curvesGraphs of the proportion of individuals of a particular age that are alive in a populationType 1 (Giant tortoise) — high survivorship until old age, then rapidly decreasing survivorshipType 2 (cedar waxwing) — survivorship decreases at a steady, regular paceType 3 (mackerel) — high morality early in life, but those that survive the early years live long lives.Age at time of reproductionA key factor determining longevity.Early reproduction will also favor early aging.Later reproduction will also favor later aging.Environmental risks and agingHigh hazard factorsIndividuals tend to reproduce earlierEarlier agingShorter life spansLow hazard factorIndividuals tend to reproduce laterLater agingLonger life spansIn environmental characterized by low morality risk, populations of slow aging individuals with long life spans evolve. In environments characterized by high morality risk, the opposite occurs.Hazard factors:High risk worldsDeath from external sourcesReproduce earlyLow risk worldsDeath from external sources lowTake home message:The rate of aging and pattern of morality in a species is determined by the hazard factor of that organisms environment.In environments characterized by low morality risk, populations of slowly aging individuals with long life spans evolveIn environments characterize by high morality risk, the opposite occurs.BIO 101 1nd Edition Lecture 20 Outline of Last Lecture II. Gene expressionIII. Inactivation of chromosomesIV. TranslationV. Cell-to-cell communicationVI. MutationsVII. CancerVIII.TelomeresOutline of Current Lecture IX. What is ecology?X. Density Dependent factorsXI. Poverty in IndiaXII. VariationCurrent Lecture What is Ecology?- Ecology is the study of interactions between organisms and their environments. It can be studied at many levels including:o Individuals Individual organismso Populations Groups of individual organism that interbreed with each othero Communities Populations of different species that interact with each other within a localeo Ecosystems All living organisms, as well as non-living elements, that interact in a particular area In your own neighborhood, which list below defines a biological community?- The animals (including humans) as well as the plants living in your neighborhood.  Population ecology is the study of how populations interact with their environments. Take home