Presentation on theme: "Populations Population- the number of individuals of a species that inhabit a particular area at the same time."— Presentation transcript:
1 PopulationsPopulation- the number of individuals of a species that inhabit a particular area at the same time.
2 2 characteristics of populations Population DensityPopulation dispersal
3 Population DensityThe number of individuals of a population that inhabit a certain area (land or water)Example) there is a population of 10 million people in los angelesGive 3 examples of population density
4 Population DispersalHow individuals in a population are dispersed or spread out in an area.
5 3 ways populations can be dispersed 1. Random- location of organisms is random and not dependent on other members of the speciesEx) dandelion seeds being randomly spread in a fieldVERY RARE
6 2. Clumping – Individuals of a population clump or flock together 2. Clumping – Individuals of a population clump or flock together ** most common kind**Ex) fish swim in schools or groupsIn this kind of dispersion animals “clump” near resources
7 3. Uniform- members of population are 3. Uniform- members of population are uniformly spread out in region or arearesults from competition for resources, members of a population need to spread out because of limited resourcesFarmers create artificial uniform distribution
8 Factors Controlling Distributions In eastern Connecticut, The Black-capped Chickadee’s moves its geographic range south in winter (summer left, winter right; darker colors are denser populations) because its physiological need for a warmer climate is better met there.WinterSummer
9 You do!What are two important characteristics of populations- explain eachName and describe three kinds of population dispersion & explain themPopulation density and dispersalRandom, uniform, clumpingPopulation density and dispersalClump, uniform, random
10 Population Growth Questions we need to be able to answer How do populations grow?What determines if populations grow or not?What patterns are there for population growth?
11 2 Factors that regulate population growth Density-dependent factors- certain factors limit growth. These include disease and availability of food and living space. As populations increase, mortality increasesDensity-independent factors- other factors influence populations regardless of their size. These include storms, forest fires, geologic events, minimum winter temperatures and snowfall amounts.
13 Two main kinds of populations: r and K Strategists/organisms r-selected/ r-strategistK-selected/k-strategistReproduce early in lifeHigh reproductive growthDon’t care for young(bacteria, amoebas)Reproduce late in lifeHave few youngDevote much time and energy to survival of youngHumans, tigers, dogs
14 Words and concepts we need to know: Biotic Potential-The amount that a population would grow if there were unlimited resources in the environmentAre there unlimited resources in an environment? What keeps populations from reaching their biotic potential?
15 Resources ARE limited in ecosystems so populations DO NOT reach their biotic potential. Organisms reach “carrying capacity”
16 Carrying Capacity (K)The maximum population size that can be supported by the available resources in an area.Different ecosystems have different Carrying capacities for different species because all species have different requirements for life!
17 You doIn a forest what populations would have a high carrying capacity? WhyWhat is the difference between biotic potential and carrying capacity?Give an example of an r-strategistGive an example of a K-strategistWhat species would have a lower carrying capacity- why?
20 1. Lag phase- population grows slowly 2.Exponential Phase- population grows rapidly/ exponentially (growth exceeds death rate)3.Stationary Phase – Population stops growing and stays relatively stable. (equal numbers of birth and death)4.Death phase- more members are dying than being born or moving in (immigration) so the population is decreasing
22 RULE OF 70The rule of 70 tells us how long it will take a population to double in sizeFormula divided by the current growth rateExample) The growth rate of a population is 5% per year. How long will it take for the population to double70/5= The population will double in.
23 PracticeUS population =311 million, growth rate is How long will it take US to double?World population is 7 billion growth rate is 1.2 How long till we double?What happens then?
24 Patterns of Population Growth 1. Logistic Population Growth- population grows fast at first then becomes stable and remains at carrying capacity- S shaped curve
25 Population cycles in ecosystems In nature populations generally follow one of two patterns
26 Boom and Bust cycleCommon among r-strategists Rapid increase followed by rapid decrease- cyclical
28 Predator Prey CyclePopulations of predator and prey influence each otherPrey population grows rapidlyPredator population grows after prey is establishedPrey begin to die outPredators die outCycle continues.
29 Find the doubling rate for a population that has a growth rate of 1.5 What two cycles of population growth exist in natureName the 4 stages of population growth and give an example of each
33 Notes in bold: How do populations change Immigration – movement of people or species into a populationEmmigration – movement of people or other species out of a population** In general these are not significant factors in population size& DO NOT affect global population ***
34 Fertility Rates Replacement level fertility (RLF) Number of children a couple must have to replace themselves2.1 in developed countries (DCs) in some less-developed ones (LDCs)Have to take infant mortality into account
35 *** TFR = most significant addition to human population****** Total Fertility Rate The number of children a woman will bear during her lifetime.Total Fertility Rate is decreasing globally however world population is still increasing.*** TFR = most significant addition to human population******
36 Projected Birth Rates by Region Which one of these countries is experiencing the most population growth?
38 Goal Total fertility rate = replacement rate Still does not equal zero population growth because of people living longer
39 Factors that affect the growth rate of Human Populations Anything that impacts TFR (total fertlility rate) impacts population growth.Examples>Availability of birth controlDemand for children in the labor forceUrbanization (rural communities have children for labor)Base level of education for womenReligious beliefs, customs and traditions
40 You do – with your partners and be ready to share in ______ Identify and describe two factors that affect TFR(total fertility rate)Explain the difference between TFR and RLF (replacement level fertility)
41 Factors not related to TFR that affect population DEATH RATE ALSO AFFECTS population!!!!The reason the worlds population has grown in the past 100 yrs is due more to later death rate than higher birth rate
42 Why are people living longer? Industrial Revolution improved standard of livingClean waterBetter sanitation (fewer diseases)Dependable food supplyBetter health care
43 2 generalization about population The more industrialized or developed the nation the longer the life spanOverall health of a population can be estimated by looking at lifespan AND mortality rate of infants.Life span: Afghanistan = 44yrs. Japan = 80yrsInfant Mortality: Afghanistan=121/1000US= 6/1000
44 You do! – think pair share What are two generalizations you can make about populations?Why are people living longer?
45 Endangered/extinction The reason so many big cats (and other species) are endangeredHabitat destroyedPrey diesPredator has no foodSpecies without food go extinct