ChapterPoupulationsPPT教学课件

1、第1页/共51页第2页/共51页 1.How many populations of organisms do you have in your envelope? In your partners envelope?Each envelope represents a community of organisms, and each color of paper clip in each envelope represents a single population. Therefore, each student should have three populations represen

2、ted. 2.Choose one of the populations in one of the envelopes. How might this population grow in size?The population (some paper clips) could reproduce, or some could move from the partners envelope into the other envelope (immigration). 3.How might this same population decrease in size?The populatio

3、n (some paper clips) could be thrown away (death), or some could move from the partners envelope into the other envelope (emigration).第3页/共51页Chapter 5 Outline51 How Populations GrowA. Characteristics of PopulationsB. Population GrowthC. Exponential GrowthD. Logistic Growth52 Limits to GrowthA. Limi

4、ting FactorsB. Density-Dependent Factors1. Competition2. Predation3. Parasitism and DiseaseC. Density-Independent Factors53 Human Population GrowthA. Historical OverviewB. Patterns of Population Growth1. The Demographic Transition2. Age StructureC. Future Population Growth 第4页/共51页51 How Populations

5、 GrowA. Characteristics of PopulationsB. Population GrowthC. Exponential GrowthD. Logistic GrowthCharacteristics of a Population1- Geographical Distribution2- Density3- Growth Rate1- Geographical Distribution-area inhabited by a population-could be as small as a few cubic centimeters like a bacteria

6、 or as large as millions of kilometers like killer whales第5页/共51页2- Population Density the number of individuals per unit How organisms are dispersed can be important Three patterns of dispersal are random, clumped, and uniform第6页/共51页3- Growth Rate- 3 factors that affect a populations size- number

7、of births- number of deaths- number of individuals entering and leaving a populationA population will increase or decrease in size depending on the number added or removed from itA population will grow if: Birth Rate Death Rate(# of individuals born) (# of individuals who die) A population will stay

8、 the same if: Birth Rate = Death RateA population will decline if: Birth Rate Death RateIndividuals entering and leaving the population will also increase or decrease a populations sizeImmigration- movement of individuals into an area (increase population)Emigration- movement of individuals out of a

9、n area (decrease population)第7页/共51页Population Growth123451. Initial growth- birth (natality) is high2. Exponential growth3. Carrying capacity- steady state4. Decline- increase in death rate5. Extinction第8页/共51页In 20 minutes the population is 2In 40 minutes the population is 4In 1 hour: the populati

10、on is 8In 2 hours: 64In 3 hours: 512In one day: 4,720,000,000,000,000,000,000Exponential Growth If a population has abundant space and food, protection from predators and disease then the organisms in the population will multiply and the population will increase Under ideal conditions with plenty of

11、 nutrients, heat, moisture, & light a bacteria can reproduce by splitting in half within 20 minutes producing 2 bacteria The pattern of growth is a J-shaped curve and the population is undergoing exponential growth Exponential growth occurs when the individuals in a population reproduce at a constan

12、t rate第9页/共51页1 million500,000100One yearPopulation sizeAt first, the number of individuals increases slowly, over time the population becomes larger and larger until it approaches an infinitely large size Under ideal conditions with unlimited resources, a population will grow exponentially第10页/共51页

13、Logistic Growth Exponential growth doesnt continue in natural populations for very long If a new species of organism is introduced into a new environment, at first the population grows slowly, then exponentially, eventually the population growth slows down (the size has not dropped, but the populati

14、on is growing slower) As resources become less available, the growth of a population slows or stops forming an S-shaped curve- logistic growth Logistic Growth occurs when a populations growth slows or stops following a period of exponential growth Birth rate decreases and death rate increases第11页/共5

15、1页Carrying Capacity When growth levels off The population is not growing Carrying capacity- the largest number of individuals that an environment can supportWhen a population overshoots the carrying capacity, then limiting factors may come into effect A balance between environmental factors must exi

16、st for a population to survive For example: Producers = consumers Water use = Rainfall第12页/共51页PopulationGrowthcan berepresented bycharacterized bycharacterized byrepresented bywhich cause aExponentialgrowthLogisticgrowthFallinggrowth rateS-shapedcurveLimits ongrowthNo limits on growthJ-shapedcurveC

17、onstantgrowth rateUnlimitedresources第13页/共51页What can limit growth?52 Limits to GrowthA. Limiting FactorsB. Density-Dependent Factors1. Competition2. Predation3. Parasitism and DiseaseC. Density-Independent FactorsLimiting Factors Any factor that causes population growth to decrease Limiting factors

18、, such as availability of food, disease, predators, or lack of space, will cause population growth to slow Under these pressures, the population may stabilize in an S-shaped growth curve第14页/共51页J curveS curveCarrying capacityExponential growthTimePopulationDISEASESPACEPREDA-TORSFOOD0Characteristics

19、 of Population Growth第15页/共51页Density-Dependent Limiting Factors A limiting factor that depends on population size is a Density-dependent limiting factor Density-dependent factors include disease, competition, predators, parasites, and food. Disease, for example, can spread more quickly in a populat

20、ion with members that live close together. Density dependent factors create an S-shaped curveOrganism Interactions Limit Population Size Population sizes are limited not only by abiotic factors, but also are controlled by various interactions among organisms that share a community.第16页/共51页第17页/共51页

21、第18页/共51页Predation affects population size Predation is a density-dependent factor When a predator consumes prey on a large enough scale, it can have a drastic effect on the size of the prey population Populations of predators and their prey are known to experience cycles or changes in their numbers

22、 over periods of time第19页/共51页Competition within a population Competition is a density-dependent factor When only a few individuals compete for resources, no problem arises When a population increases to the point at which demand for resources exceeds the supply, the population size decreases Compet

23、ition can also occur between members of different species- this creates evolutionary change The two species competing are under stress to change in way that decrease competition- eventually evolving to occupy separate niches第20页/共51页Predation affects population size The data in this graph reflect th

24、e number of hare and lynx pelts sold to the Hudsons Bay Company in northern Canada from 1845 through 1935.Lynx and Hare Pets Sold to the Hudsons Bay CompanyNumber of organisms in thousands)Times (in years)LynxHare第21页/共51页MooseWolves The periodic increase in the moose population is quickly followed

25、by a rise in the number of wolves. This increase in the number of wolves increases the number of moose captured by their predator and the moose population drops. The wolf population will then decrease after the moose numbers drop because the wolves are less able to find food. The predator prey cycle

26、 can be repeated indefinitely.第22页/共51页Parasitism and Disease Parasites can also limit a populations size-density-dependent As the # of individuals , parasites which then causes the # of individuals to Parasites are similar to a predator in that they take nourishment at the expense of their host As

27、a population increases in size, disease is more common because individuals are in closer contact with one another第23页/共51页Density-independent limiting factors and population growth Density-independent factors can affect all populations, regardless of their size Most density-independent factors are a

28、biotic factors, such as temperature, storms, floods, drought, and major habitat disruption第24页/共51页Density-Independent Factors Density-independent factors create a boom-and bust curve (exponential growth followed by a sudden collapse) Examples: Weather- a drought kills grass Human activity: deforest

29、ation- destroys habitat Seasons: a severe winter regulates insect population第25页/共51页Boom-and-Bust CurveTimePopulation Density第26页/共51页Limitations on Population Growth第27页/共51页Reproduction Patterns In nature, animal and plant populations change in size. Biologists study the factor that determines po

30、pulation growthan organisms reproductive pattern, also called its life-history pattern A variety of population growth patterns are possible in nature- R strategists and K-strategists第28页/共51页Rapid life-history patterns- R Strategists rapid life-history patterns are common among organisms from change

31、able or unpredictable environments rapid life-history organisms have a small body size, mature rapidly, reproduce early, and have a short life span第29页/共51页Slow life-history patterns K-strategists large species that live in more stable environments usually have slow life-history patterns. reproduce

32、and mature slowly, and are long-lived. They maintain population sizes at or near carrying capacity第30页/共51页Demography Demography, the study of human population size, density and distribution, movement, and its birth and death rates Demography examines the characteristics of human populations and att

33、empts to explain how those populations will change over time Demographic transition- a change in a population from high birth and death rates to low birth and death rates; Examples- United States and Japan 53 Human Population Growth A. Historical Overview B. Patterns of Population Growth1. The Demog

34、raphic Transition2. Age Structure C. Future Population Growth 第31页/共51页AgriculturebeginsPlowingand irrigationBubonicplagueIndustrialRevolutionbeginsHuman Population GrowthAgriculture beginsPlowing and irrigationBubonic plagueIndustrial Revolution BeginsUntil about 500 years ago, the population grew

35、slowly. Agriculture and industry made life easier and safer.第32页/共51页Human Population We are growing exponentially Due to technological advances: medicines, a dependable food supply, and sanitation The death rate is decreasing and the life expectancy is increasing The human population will eventuall

36、y reach its carrying capacity第33页/共51页Population Distribution Per Age Range for Several CountriesAgeStable growthRapid growthSlow growthMaleFemaleReproductive yearsPopulation (percent of total for each country)Age Structure Population growth depends on how many people of different ages make up a giv

37、en population Demographers can predict future growth using age-structure diagrams Age-structure diagrams graph the number of people in each age group第34页/共51页U.S. PopulationRwandan PopulationAge Structure第35页/共51页Ch.6-2: Human Impact on the Environment Air Greenhouse effect Trapping of heat by gases

38、 in the Earths atmosphere (carbon dioxide) This may lead to global warming- increase in the Earths temperature from the rapid buildup of carbon dioxide and other greenhouse gases Acid Rain Burning of fossil fuels release nitrogen and sulfur into the atmosphere which combined with water form nitric a

39、nd sulfuric acid Acid Rain kills plants Smog Mix of chemicals in the air from automobile exhaust Affects the respiratory system especially those with asthma第36页/共51页Emissions to AtmosphereNitrogen oxidesSulfur dioxideChemical TransformationNitric acidSulfuric acidPrecipitationAcid rain, fog,snow, an

40、d mistDry FalloutCondensationparticulates, gasesIndustryTransportationOre smeltingPower generationSection 6-2 The Formation of Acid Rain第37页/共51页Human Impact of the Environment Water Excessive nutrients can cause an increase in algae growth and depletion of oxygen for other organisms Over harvesting

41、 of fish has reduced the number of fish 第38页/共51页Human Impact of the Environment Land Erosion The wearing away of surface soil by water and wind Desertification The combination of farming, overgrazing, and drought in dry climates which turn productive areas into deserts Deforestation The loss of for

42、ests which leading to severe erosion and changes in soil properties Deforestation erosion water pollution and desertification第39页/共51页Consequences If humans continue to alter the environment, they will have to deal with the results Examples: fossil fuels combustion, habitat destruction, deforestatio

43、n, ozone layer destruction, global warming Human Overpopulation results in: Worldwide malnutrition Increased disease Increased pollutionHumans need to learn to be a part of nature not apart from nature!第40页/共51页Ch. 6-3: Biological Diversity Ecosystem diversity- variety of habitats, communities, and

44、ecological processes in the living world Species diversity- the number of different species Genetic diversity- sum total of all the different forms of genetic information carried by all organisms living on Earth today Biodiversity increases as you move toward the equator. Areas around the world diff

45、er in biodiversity Biodiversity can bring stability to an ecosystem.Biodiversity is one of the worlds greatest resources第41页/共51页Variations within a species also helps protect against disease or parasite Genetically different individuals within a species have a better chance of resisting disease Exa

46、mple: world cheetah population reduced by a single virus Tree plantation has same type of trees (single species) vulnerable to disease, etc.- spread easily Diversity among individuals in a population is important to resistance of population as a whole (genetically different) Biological diversity cau

47、ses ecological stability第42页/共51页Adaptations- changes in response to factors in the environment (physical and behavioral changes) Slow process that takes place over many generations Organisms can be specialized to occupy a specific niche Advantages The more specialized an organisms method of obtaini

48、ng food and life requirements are (NICHE), the less competition they will have with other species (they have a better chance of surviving) Example: anteater with long snout can reach into ant hills Disadvantages If there are changes in the environment, organisms may not be able to adapt fast enough

49、in response Example: Koala bears eat only Eucalyptus trees第43页/共51页InsectsBacteriaFungiPlantsProtistsOther Animals54.4%4.2%18%3.4%0.3%19.7%Species Diversity第44页/共51页Loss of Biodiversity Extinction is the disappearance of a species when the last of its members dies Extinction is a natural process and

50、 Earth has experienced several mass extinctions during its history A species is considered to be an endangered species when its numbers become so low that extinction is possible第45页/共51页Threats to Biodiversity Complex interactions among species make each ecosystem unique Changes to habitats can therefore threaten organisms with extinction Human activity can reduce biodiversi