Unit IV -Population Dynamics
Size– Increased by
• Births and Immigration
– Decreased by• Deaths and Emigration
– CalculationsGrowth
rate
Birth
rate
Death
rate
Immigration
rate
Emigration
rate
r = (b – d) + (i – e)
Local Population Changes
Global Population Changes
DensityWhat is it?
# of organisms/habitat space
Does the predator or the prey control it?They both do!
Density Independent FactorsFactors independent of # of organisms in habitat.
climate, natural disaster, habitat space
Density Dependent FactorsFactors depend on # of organisms in habitat.
predation, disease, competition
Maximum Population Sizes
Environmental Limits
Prevent unlimited reproduction
Unfavorable food, water, shelter, predation, etc.
Carrying Capacity (K)
Maximum # of individuals an environment can support
Growth Curves
Slope of line on population growth chart indicates two different patterns of increase.
S-CurveLogistic Curve
Indicates growth with stable populations once K is reached.
J-CurveExponential Growth
Populations overshoot resources and crash
Boom-and-bust populations
J-CurveBoom-and-bust populations
J-CurvePredator-Prey Dynamics
As the predator population increases, the prey population decreases (and vice versa)
DispersionWhat is it?
Uniform, random distribution, or clumping of populations.
What affects it?
Availability of resources and/or species’ niches
Age Distribution• Based on:
how many individuals are reproductive and how long they stay that way.
• R-Strategists – R=Reproductive Potential– High birth rates, little parental care, reproduce quickly, have
cyclic growth rates, generalists species– J-Curve growth rates
• rodents, insects
• K-Strategists– K= Carrying Capacity– Lower birth rates, high parental care, slow to mature, stable
growth rate, specialists species– S-Curve growth rates
• large mammals
Age DistributionSurvivorship Curves
Indicate trends in populations related to the # of individuals at each age.Late Loss (Type I)
typically K-strategistshigher parental care, low juvenile mortality
elephants, whales
Constant Loss (Type II)intermediate reproductive strategiesconstant rate of mortality at all ages
songbirds, lizards
Early Loss (Type III)typically R-strategistslittle parental care, high juvenile mortality
bony fishes, rodents
Age DistributionSurvivorship Curves
Human Population GrowthDemography
Study of population vital statistics
Agricultural RevolutionOccurred ~8000 BCE
hunter-gather → farming societies
World population still did not reach 1,000,000,000 for another 10,000 yrs.
Industrial RevolutionOccurred ~1800
Triggered the largest increase in population in history.
In less than 200 yrs global population increased from 1 billion to 7 billion.
Number of Years to Add One Billion People to the World Population
Global Pop.
Date Achieved
Years Required
1 billion 1800 All of human history
2 billion 1930 130
3 billion 1960 30
4 billion 1974 14
5 billion 1987 13
6 billion 1998 11
7 billion 2011 13
Human Population Growth
Population increase in Mexico
Human Population GrowthCurrent world population is ~ 7 billion
7,569,861,660 (Sept 2017 est)
Current world population growth rate is 1.11%
The growth rate is declining, but the population is still increasing.
Projections for 2050
Low = 7.8 billion
High = 10.8 billion
Most likely = 9.2 billion
Human Population Growth
World’s Most Populous Countries
1. China – 1.379 billion – 0.46%
2. India – 1.281 billion – 1.2%
3. USA – 326 million – 0.73%
4. Indonesia – 260 million – 1.17%
5. Brazil – 207 million – 0.83%
6. Pakistan – 204 million – 2.07%
7. Nigeria – 190 million – 2.63%
8. Bangladesh – 157 million – 1.19%
9. Russia – 142 million – -0.01%
10. Mexico– 124 million – 1.27%
Human Population Growth- 2012World’s Fastest Growing Nations
5. Qatar – 2.1 mil – 3.58%
4. Jordan – 7.9mil – 3.86%
3. South Sudan – 11.5mil – 4.12%
2. Zimbabwe – 13.8mil – 4.36%
1. Lebanon – 5.9mil – 9.37%
World’s Fastest Shrinking Nations
5. Latvia – 2.1mil – -0.64%
4. Ukraine – 44.3mil - -0.64%
3. Estonia – 1.2mil - -0.68%
2. Bulgaria – 6.9mil - -0.83%
1. Moldova – 3.6mil - -1.02%
*Syria – 17.9mil - -9.73%
Demographic TransitionPre-Industrial Stage- Birth and death rates high- Modest population growth
Transitional Stage- Lowered death rate- Rapid population growth
Industrial Stage- Lowered birth rate- Slow population growth
Post-Industrial Stage- Low birth and death rates- Population growth very low or negative
Carrying Capacity of the PlanetWhat is it?
Depends on the model
Difficult to determine until it has been reached.
Humans vs. Other Animals
Greatest difference is the death rate.
Human birth defects occur at a much higher rate.
Population Size FactorsFamily Planning
Necessary part that includes choosing the # and the spacing of children.Families must balance their needs vs. wants
Replacement Level Fertility
Total Fertility Rate
Role of FemalesAge & number of females influence human population structure.~½ of world’s females are of child bearing age.
Cultural and Religious BeliefsHas possibly most significant influence on birth rates.
Population Size Factors
Cultural TraditionsCulture influences and control individuals’ behaviors
Age of marriage
Necessity of children in workforce
High infant mortality
Religious values
Population Size Factors
Social & Economic Status of Women
Gender inequality is common worldwide
Social status
Economic status
Legal rights
Education
Employment and salaries
Population Size Factors
Social & Economic Status of Women
Women with more education tend to
Marry later
Have fewer children
Population Size FactorsFamily Planning
Offering information to both men and women on contraception, STDs, parenting, and sexuality
Government PoliciesChina
Incentives to promote later marriages and 1 child familiesBrought rapid & drastic decrease in fertilityBrought pressure to abort/kill female 1st child
India1950 - 1st national government-sponsored family planning
Unsuccessful due to cultural barriers
1976 – Incentives for sterilizationUnpopular and failed
Recently has focused on educationMuch more successful
Human Health
Two main indicators of human health
Life expectancy
Infant mortality
How many children die before age 1
Vary GREATLY between developed and developing nations
Human Health - DevelopedAverage Life Expectancy
Men = 75yrs
Women = 80yrs
Highest is Monaco at 89.57 years
Leading causes of death
1. Heart Disease
2. Cancer
3. Lung Disease
Most premature deaths are caused by lifestyle choices
Poor diet, lack of exercise, smoking, obesity
Human Health - Developing
Average Life Expectancy
65 yrs
Lowest is Chad at 49.44 years
Biggest issues
Malnutrition, unsafe water, poor sanitation
Childhood mortality is high
Transmissible diseases
Diseases and IllnessesNon-transmissible Diseases
Diseases not caused by living organisms.
Diseases cannot be spread from one person to another
Ex: heart disease, cancer, diabetes
Transmissible Diseases
Diseases caused by living organisms
Pathogens - infectious agents
bacteria, viruses
Diseases can be spread from one person to another
Vectors – non-human carriers
air, water, food, animals
• ~80% are water born
Diseases and IllnessesOld World (Reemerging) vs. New World (Emerging) Diseases
Malaria = Old
West Nile = New
Developed Nations~8% of deaths are from infectious disease
1 doctor for every 500 people
Developing Nations~40% of deaths are from infectious disease
In E. Africa - only 1 doctor for every 600,000 people.
World’s 7 Deadliest Infectious DiseasesPneumonia and Flu
bacteria & viruses
HIV/AIDSVirus
Diarrheal Diseasesbacteria & viruses
TuberculosisBacteria
Malariaprotozoa
Hepatitis Bvirus
Measlesvirus
ToxicologyWhat is it?
Study of adverse chemical effects on health.
Measures how harmful a substance is.
Toxicity
Acute
Effects occur within a short period of exposure
Chronic
Effects occur some time after exposure
Effects occur after prolonged exposure
Factors Affecting ToxicityMovement and Distribution Influences
Genetic Makeupof the organism it will affect
SolubilityAbility of a toxin to break down in the environment.
PersistenceHow often a toxin attempts to be absorbed into the environment.
FrequencyHow often a toxin is exposed to the environment.
Biomagnification/Bioaccumulation
Factors Affecting Toxicity
Determined by LD50– Level at which a
chemical kills 50% of the test populations with a single dose within 14 days.
LD = Lethal Dose
50 = 50% mortality of the test population
– AKA: median lethal dose
Factors Affecting ToxicityDose
Amount of exposure either singularly or accumulated.
ResponseType of damage
temporary or permanent
Dose-Response CurveShows the effects of various doses of a toxin on a particular organism.
Factors Affecting Toxicity
Risk Assessment Limitations
Laboratory Testing Limitations:
Lab rats are different from humans.
May not identify what other chemical exposures occurred or what habits a person has.
May not show the effects of chemical interactions.
Testing may be too costly and slow to use on every chemical.
Groupings of Toxic ChemicalsMutagens
alter chromosomes
Teratogens
congenital defects
fetus is deformed or diseased
Carcinogens
known to cause cancer
Neurotoxins
attack the nervous system
Asphyxiates
interfere or exclude O2 uptake
Allergens
attack the immune system
Risk Assessment
Risk
Probability that a particular adverse effect will result from some exposure or condition.
Four primary steps
Hazard ID
Dose-Response Assessment
Exposure Assessment
Risk Characterization
Urban AdaptationsUrban Areas
Defined as areas with more than 25,000 people.~300 cities with populations over 1,000,000.The 2000’s was the first time people lived in urban than rural areas.
ProsBetter access to education, health care, jobs.Reduce destruction of wildlife habitats, protects biodiversity.
ConsHigher concentrations of pollutants and infectious diseases.Infrastructures are more expensive to repair.