Presentation on theme: "Intro to Chapter 16 – Human pops"— Presentation transcript:
1 Intro to Chapter 16 – Human pops Population Ecology(chapter sect 3 and 4)Intro to Chapter 16 – Human popsEach population hasA DensityA DispersionA Reproductive Strategy
2 PopulationA group of the same species of organism living in the same placeUnderstand food chains and food websWhat might effect the survival of THIS group of dolphins?
3 Characteristics of Populations 4 Major Characteristics of Populations:Geographic DistributionDensityGrowth RateAge Structure
4 1. Geographic Distribution Area inhabited by a population*remember, there are also ecological equivalents in similar ecosystems around the planet, but if they are not in the same habitat, they are NOT the same population!
5 Population dispersion Way in which individuals of a population are spread in an area or a volume3 types:Dispersion patterns -- page 437 in textbookClumped Uniform Random
11 3. Growth RateHow fast a population is growing/shrinking
12 Negative & Positive Growth Positive growth: net increaseTotal penguin population was 1200 at the beginning of the year, now is 1600.Negative growth: net decrease250 penguin chicks died during the year.
13 Biotic PotentialThe maximum rate at which the population of a given species can increase when there are no limits on its growth.“living” potentialIt is not possible for a population to increase FOREVER – there are limitations!
14 Factors affecting population growth Immigration:movement into an areaEmigration:movement out of an area***approach maturity & move out***shortage of resourcesBirth RateChange in # birthsDeath RateChange in # deaths***increase/decrease birth & death rates***birth = death?
15 Types of Population Growth Exponential GrowthLogistic Growth
16 1. Exponential Growth J-shaped curve reproduce at a constant rate Slowly at first, then larger until approaches infinitely large size.ideal conditionsunlimited resources
17 2. Logistic Growth S-shaped curve Carrying Capacity- How could growth Slow increase, larger increase when large number of resources, then slows when resources become less available, growth slows/stops, oscillates around carrying capacity.Carrying Capacity-largest # individuals environment can supportTells size of population when average growth rate reaches zero.How could growthslow or stop?
18 How population growth may slow: Birth rate decreasesDeath Rate IncreasesBoth occur at the same rateReason why these change Limiting factors
19 Limiting Factorscauses population growth to decrease
20 1. Density Independent Factors Do not depend on population sizeEx:Unusual weathernatural disastersseasonal cyclesdamming riversclear-cutting forests
21 2. Density-Dependent Factors depends on population size.CompetitionPredationParasitesDiseasesCompetitionPredationParasitesDiseaseslarger populations are more affected by density-dependent factors(orgs are closer together)
22 ApplicationQ1: Think about the black racer snake populations in Georgia. Once a pair of mice start reproducing, what would happen to the black racer snake populations, and why?
29 Interspecific Competition Competition between different species for the same resources.wildebeast and rhinovultures and hyenas
30 Intraspecific Competition Competition between members of same species for similar resources.heronslionsBunchgrass in Mojave Desert – roots compete
31 1b. Parasitism and Disease Parasite or disease-causing organism takes nourishment from host, weakens/kills hostspreads quicker w/ greater density.Wasp Cocoons This larval sphinx moth has been attacked by a parasitic wasp. The wasp inserted its eggs beneath the moth’s skin. After hatching, the wasp larvae fed on their host internally until they appeared as white cocoons on its back.
34 Demography Study of human population growth characteristics Looks at growth rate, age structure, geographic distributionCan tell if pop is growing by looking at the difference between the birth rate and the death rateIn US, death rate is declining, life expectancy is increasing, fertility rate is decreasing – WHY?
35 Age-Structure diagrams or Population Pyramids Describes how many individuals of different ages make up a populationPopulation Pyramids, or Age-Structure Diagrams, show age structure in a population.Populations with large numbers of young offspring have greater potential for rapid growth
37 Comparing Human Populations… Expansive Constrictive Near Stationary
38 Patterns of Population Growth… The Demographic transition- A change in a population from high birth and death rates to low birth and death rates.
39 Human Population on Earth Thomas Malthus – economist, late 1700’s*wrote an essay that stated that human population was growing faster than the Earth’s resource could supportToday’s human population exceeds 6 billion…
41 Carrying capacity and humans Carrying capacity for human pop has changed due to technologyDue to improvements in:Agriculture, transportation, medicine, sanitation
42 Nonrenewable vs. renewable resources Nonrewable – used faster than they formex. Coal and oilRenewable – cannot be used up or can replentish themselves over timeex. Wind energyIf not used carefully, renewable COULD become nonrenewableEx. Water – pollution often makes it unusable
43 U.S. uses more resources and produces more waste…. Than any other country on the planetex. 230 million tons of garbage/year (4.2 lbs per person per day)Ecological footprint:The amount of land necessary to produce and maintain enough food and water, shelter, energy, and wasteDepends on: amount and efficiency of resource use, and the amount and toxicity of waste producedSee textbook page 487 for world view