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.