Chapter 6Chapter 6

Population DynamicsPopulation Dynamics

Objective 1 & 2Objective 1 & 2

Appreciate the potential of Appreciate the potential of exponential growthexponential growth

Draw a diagram of the J and S curves Draw a diagram of the J and S curves and explain what they meanand explain what they mean

What is Exponential What is Exponential Growth?Growth?

Exponential growthExponential growth

Exponential growth is said to follow Exponential growth is said to follow an an exponential lawexponential law; the simple-; the simple-exponential growth model is known exponential growth model is known as the Malthusian growth model. as the Malthusian growth model.

For any exponentially growing For any exponentially growing quantity, the larger the quantity quantity, the larger the quantity gets, the faster it grows. An gets, the faster it grows. An alternative saying is 'The rate of alternative saying is 'The rate of growth is directly proportional to the growth is directly proportional to the present size' present size'

Exponential GrowthExponential Growth

We are familiar with geometric growth in the We are familiar with geometric growth in the context of compound interest. You put $1000 in a context of compound interest. You put $1000 in a savings account. Suppose that the account pays savings account. Suppose that the account pays 4 percent interest annually. How much will you 4 percent interest annually. How much will you have in the bank after 10 years?have in the bank after 10 years?

The basic equation for growth is YtThe basic equation for growth is Yt = = Y0(1+r)tY0(1+r)t

where Y0 is the initial amount ($1000 in this where Y0 is the initial amount ($1000 in this example), r is the growth rate expressed as a example), r is the growth rate expressed as a decimal (.04 in this example), and t is the number decimal (.04 in this example), and t is the number of years of growth (10 in this example). The of years of growth (10 in this example). The amount you will end up with after 10 years is amount you will end up with after 10 years is $1000(1 + .04)10 = $1480.24.$1000(1 + .04)10 = $1480.24.

Which is Which?Which is Which?

Which Type of Growth is Which Type of Growth is which?which?

Geometric growthGeometric growthon a graphon a graph

Population growth Population growth rate is expressed rate is expressed as a fraction: as a fraction: the population is the population is calculated by calculated by multiplying multiplying

(J curve results)(J curve results)

SLOW AT FIRST, SLOW AT FIRST, THEN HUGE THEN HUGE GAINS!!!!!!!!!!GAINS!!!!!!!!!!

Arithmetic growthArithmetic growth

The population is The population is growth at a growth at a constant constant amount per amount per time. (linear time. (linear curve results)curve results)

STEADY RISE IN STEADY RISE IN POPULATIONPOPULATION

Are both found here?Are both found here?

What does this graph say?What does this graph say?

What is a J CURVE?What is a J CURVE?

Short gains earlyShort gains early Big gains laterBig gains later Population is meeting/exceeding Population is meeting/exceeding

biotic potentialbiotic potential Theoretical unchecked growthTheoretical unchecked growth This is real for some populations This is real for some populations

(bacteria in particular…..but not (bacteria in particular…..but not ALWAYS!)ALWAYS!)

J curveJ curve

What is an S CURVE?What is an S CURVE?

The result of a population growth The result of a population growth that has experienced environmental that has experienced environmental resistance.resistance.

NOTE: what happens to the NOTE: what happens to the influence of Env. Resistance as the influence of Env. Resistance as the population approaches the carrying population approaches the carrying capacity?capacity?

S curveS curve

What factors can we glean What factors can we glean fromfrom

the S (Sigmoidal) curve?the S (Sigmoidal) curve? All populations have some limits.All populations have some limits. Reading a S curve can reveal those Reading a S curve can reveal those

limits or at least give you an idea limits or at least give you an idea that are limits to look for.that are limits to look for.

What limited our growth for so What limited our growth for so long????long????

Objective #3Objective #3

Who was Thomas Malthus and what Who was Thomas Malthus and what did he say about population growth?did he say about population growth?

Thomas MalthusThomas Malthus 1818thth century Economist century Economist link to articlelink to article

““Elevated as man is above all other animals by Elevated as man is above all other animals by intellectual faculties, it is not to be supposed that the intellectual faculties, it is not to be supposed that the physical laws to which he is subjected should be physical laws to which he is subjected should be essentially different from those which are observed to essentially different from those which are observed to prevail in other parts of animated nature. He may prevail in other parts of animated nature. He may increase slower than most other animals, but food is increase slower than most other animals, but food is equally necessary to his support; and if this natural equally necessary to his support; and if this natural capacity of increase be greater than can be capacity of increase be greater than can be permanently supplied with food from a limited permanently supplied with food from a limited territory, his increase must be constantly retarded by territory, his increase must be constantly retarded by the difficulty of procuring the means of subsistence’. “the difficulty of procuring the means of subsistence’. “

Population OscillationsPopulation Oscillations

So what did he say?So what did he say?

Populations are cyclicPopulations are cyclic They will flux with the environmentThey will flux with the environment Famine, disease, war…all affect Famine, disease, war…all affect

populationpopulation

Europe: 0-2000 Europe: 0-2000

And the US?And the US?

Populations go thru one of two Populations go thru one of two types of growth:types of growth:

Irruptive or Malthusian Growth (unstable)Irruptive or Malthusian Growth (unstable)Peaks, diebacksPeaks, diebacks

OROR

Logistic growth (stable)Logistic growth (stable)Constantly changing rateConstantly changing rate

Be able to discuss Be able to discuss the pros and cons of each.the pros and cons of each.

Objective #4Objective #4

Discuss environmental resistance Discuss environmental resistance and discuss how it can lead to and discuss how it can lead to logistic or stable growthlogistic or stable growth

Malthusian StrategiesMalthusian Strategies

Low tropic levels, pioneer species, Low tropic levels, pioneer species, primary successionprimary succession

Move into disturbed environs, mature Move into disturbed environs, mature early, make many offspring, don’t care early, make many offspring, don’t care for them, rely on sheer numbersfor them, rely on sheer numbers

Insects, rodents, parasites, annual Insects, rodents, parasites, annual plantsplants

Limited by predators, Limited by predators, overshoot/diebacks, adapt quicklyovershoot/diebacks, adapt quickly

Extrinsic characteristics (pg. 129)Extrinsic characteristics (pg. 129)

Logistic StrategiesLogistic Strategies

Larger, live longer, mature more Larger, live longer, mature more slowly, produce less offspring, have slowly, produce less offspring, have fewer predators, care for offspring fewer predators, care for offspring longerlonger

Wolves, elephants, bears, primatesWolves, elephants, bears, primates intrinsic characteristics (pg. 129)intrinsic characteristics (pg. 129)

Objective #5Objective #5

Define fecundity, fertility, birth rates, Define fecundity, fertility, birth rates, life expectancy, death rates, life expectancy, death rates, survivorshipsurvivorship

FecundityFecundity

The physical ability to reproduceThe physical ability to reproduce

NatalityNatality

Producing of new individuals through Producing of new individuals through hatching, birth, germination or hatching, birth, germination or cloningcloning

fertilityfertility

A measure of the offspring producedA measure of the offspring produced

Birth RatesBirth Rates

Crude birth rates for many countries iCrude birth rates for many countries is declining…..s declining…..

Life expectancyLife expectancy

Life expectancy calculatorLife expectancy calculator

Living to 100Living to 100

Death ratesDeath rates Causes of  Death Number of Deaths Rate per 100,000 Causes of  Death Number of Deaths Rate per 100,000  15-24 years 15-24 years All causes All causes 32,69932,699   Accidents and adverse effects Accidents and adverse effects 13,87213,872 Motor vehicle accidents Motor vehicle accidents 10,62410,624 All other accidents and adverse effects All other accidents and adverse effects 3,248 3,248  Homicide and legal intervention Homicide and legal intervention 6,548 6,548  Suicide Suicide 4,3694,369 Malignant neoplasms, including neoplasms of lymphatic and hematopoietic Malignant neoplasms, including neoplasms of lymphatic and hematopoietic

tissuestissues1,6421,642   Diseases of heart Diseases of heart 920 920  Human immunodeficiency virus infection Human immunodeficiency virus infection 420 420  Congenital anomalies Congenital anomalies 387 387  Chronic obstructive pulmonary diseases and allied conditions Chronic obstructive pulmonary diseases and allied conditions 230 230  Pneumonia and influenza Pneumonia and influenza 197197   Cerebrovascular diseases Cerebrovascular diseases 174174   All other causes (Residual) All other causes (Residual) 3,9403,940

More death rate statistics More death rate statistics  Countries death ratesCountries death rates

survivorshipsurvivorship

The The percentage percentage of offspring of offspring born at the born at the same time same time that that survives to survives to a certain a certain ageage

Objective #6Objective #6

Compare and contrast density Compare and contrast density dependent and density independent dependent and density independent population processespopulation processes

Density-Independent Density-Independent FactorsFactors

Abiotic components of the ecosystemAbiotic components of the ecosystem

Density-Independent Density-Independent FactorsFactors

Natural disasters or extreme weather Natural disasters or extreme weather events can help or hurt a populationevents can help or hurt a population

What effect did this eruption What effect did this eruption have on the habitat? The have on the habitat? The

organisms?organisms?

Weather Patterns with a Global Weather Patterns with a Global Impact!Impact!

Do these occurrences really Do these occurrences really REGULATE the population?REGULATE the population?

Density-Dependent FactorsDensity-Dependent Factors

Reduce the population sizeReduce the population size Drop in natality or increase mortalityDrop in natality or increase mortality HOW?HOW?

Either:Either: Intraspecific interactionsIntraspecific interactions Interspecific interactionsInterspecific interactions

Predator-Prey cyclic Predator-Prey cyclic relationsrelations

Who do I prey on? Who do I prey on?

What might cause this What might cause this change?change?

Stress and CrowdingStress and Crowding

The SummaryThe Summary

The summary is very good.The summary is very good.

A must read for all.A must read for all.