Unit 7 Human Population Ecology & Human Health Chapter 10 & 19 https://www.youtube.com/watch?v=E8dkWQVFAoA

Crash Course Human Population

Changes in population size are due to inputs (births & immigration) and outputs (deaths and emigration)

Demographers use:

Crude birth rate = # births per 1000 individuals per year

Crude death rate= # of deaths per 1000 individuals per year

Calculating Growth Rate Example

In 2014, worldwide, there were 20 births and 8 deaths per 1000

([CBR-CDR]/1000)(100) = [20-8]/10 = 1.2%

*For one nation ([CBR + i]-[CDR + e]/1000) (100)

Developed countries - crude birth & death rates closer

Developing countries - higher crude birth rates than death rates

([CBR-CDR]/1000)(100)

Reasons for human population increase: – Movement into new habitats and climate zones

– Early and modern agriculture methods

– Control of infectious diseases through:

• Sanitation systems

• Antibiotics

• Vaccines

Most population growth occurred over last 100 years due to drop in death rates (not increase in birth rates)

Human Population Size – Exponential pop growth has slowed, but population is at about 7 billion

• Pop growth rate in developed countries: 0.1%

• Pop growth rate in developing countries: 1.5%

• Top growing countries: India, China, Pakistan, Nigeria, Bangladesh, & Indonesia

Doubling Time: The time it takes for a population growing at a

specific rate to double its size

*Rule of 70: quick way to calculate doubling time

70_________ = doubling time

percentage growth rate

Example: Growth rate in 2004 was 1.5%. If that rate continues, how many years will it take for the population to double?

Answer: 70/1.5 = ~47 years

Fertility: number of births that occur to an individual woman or a

population

Two types of fertility rates affect a country’s pop size & growth rate:

1.Replacement level fertility: number of children a couple must bear

to replace themselves.

Typically a bit higher than 2 due to some females dying before reproductive

age. (developed countries = 2.1, developing as high as 2.5 children)

2.Total Fertility rate (TFR): Average number of children a woman

typically has.

Global TFR = 2.8 kids, Developed = 1.6, Developing = 3.1

• United States:

≈300 million people

Birth Rates

• Now near

replacement level

• Most recent peak

was the WW II

Baby Boom

U.S. Growth Rate Still growing faster than any other developed

country; One reason: IMMIGRATION! accounts for ~41% of U.S.’s

annual pop growth; Only 3 countries encourage immigration: Canada,

Australia, United States

Factors Related to Lowering Birth Rates:

• Children enter the work force later

• Raising and educating children is expensive

• Retirement/pension systems means less children have to support

elderly parents

• Urbanization (kids are not needed to work on farms)

• Higher education and employment rates of women

• Lower infant mortality rate

• Higher age at marriage (fewer kids when marry at 25+)

• Availability of legal abortions

• Availability of reliable birth control methods

• Religious and cultural beliefs

Lowering Death Rates:

Improvements in health care, nutrition, sanitation, water supplies lead to a higher life expectancy & lower infant mortality Life expectancy = average # of years a newborn infant can expect to live

Infant mortality rate = # babies out of every 1,000 born who die before 1 year old

Global life expectancy ~ 67 years

Developed country life expectancy = 77 years

Developing country life expectancy = 65 years

(Africa = 49 years *AIDS)

Infant Mortality: Indicator of society’s quality of life

•High infant mortality suggests insufficient &/or poor food, and

high disease

Developed country infant mortality ~ 7

Developing country infant mortality ~ 61

•U.S. infant mortality relatively high among developed countries

b/c Inadequate health care, Drug addiction, Teen pregnancies

Age Structure= double sided bar graph showing age & gender

distribution

3 groupings

Pre reproductive: 0-14 years

Reproductive: 15-44 years

Post reproductive: 45+

Shape indicates population growth trend

Large base means many pre

reproductive individuals pop

growth

(many young people= growth in future)

Age Structure (U.S. Baby Boom)

By ~ 2030, 1 of every 5 people will be 65+

Effects of Population

Decline

~40 countries have

stabilized or declining

pops

*higher proportions of

older people

– Effects:

• Higher medical care costs

• Depleted social security

• Fewer tax payers

• Affects immigration

(need workers)

Japan, Russia, Germany, Bulgaria,

Hungary, Ukraine, Serbia, Greece,

Portugal, & Italy

Three most important steps to slow human population growth:

1. Reduce poverty through economic development & education

2. Elevate the status of women

3. Encourage family planning & reproductive health care

Step1: Promoting economic development

Step 2: Empowering Women

Women who have the right to an education & work have less children

Poor, illiterate women have 5-7 children compared to literate who have <2

Depends a lot on cultural & religious beliefs in role of women Step 3: Family Planning Family planning is responsible for a drop of at least 55% in TFRs in developing countries (from 6 in 1960 to 2.7 in 2010)

Ex: Thailand cut pop growth rate from 3.2% in 1971 to 0.6% in 2010

~40% of all pregnancies in developing countries are unplanned & 26% end in abortion (US had ~1.3 mil abortions in 2007)

Solutions: expand family planning to include teenagers & unmarried women, educating men/birth control for men?

Demographic Transition Model: As countries become industrialized

& economically developed, first their death rates decline, then their birth rates decline

– Stage 1 - Preindustrial: high birth & death rate (slow growth)

– Stage 2 - Transitional: high birth rates & death rates drop

b/c of better food & health (pop grows rapidly)

– Stage 3 – Industrial: birth & death rates drop (Pop growth

slows)

– Stage 4 – Postindustrial: pop growth stabilizes or declines

Developed countries in Stage 3 or 4 Developing countries either in Stage 2 or some in Stage 1 (Africa

dealing with AIDS)

U.S.

Brazil

Kenya

– China -World’s most populous country – 1.3 billion

people

• 1960s – serious threat of mass starvation due to pop growth

– Established one-child per family policy

» Gov provides contraceptives, sterilizations, and abortions for

married couples

» Married couples pledge to have 1 kid – get better housing, more

food, free health care, etc.

» TFR in 1972 was 5.7, in 2010 was 1.5

– India -World’s 2nd largest pop; projected to be largest

in 2015

• 1952 family planning began, but only moderately successful

• TFR is ~ 2.6 b/c (1) couples believe need children to care for

them in old age, (2) cultural preference for males

Population Campaigns

Human Health

Chapter 19: Risk, Toxicology, and Human Health

Risk: probability of suffering harm from a hazard

that can cause injury, disease, death, economic loss,

or damage

Risk assessment: using stats to

estimate amount of harm

Risk management: deciding how

to reduce risk and at what cost

Types of Hazards:

Biological hazards: pathogens, pollen, venomous animals

Pathogen: organism that causes disease: bacteria, viruses,

parasites, protozoa, & fungi

Chemical hazards: in air, water, food, man-made products

Cultural hazards: unsafe working conditions, driving, crime

Natural hazards: fire, storms, etc.

Lifestyle choices: smoking, unsafe sex, drinking/drugs, etc.

Greatest Health Risks: in the US

• 1. Poverty: malnutrition, disease (normally nonfatal)

– Shortens lifespan by 7-10 yrs

• 2. Gender

– Being male shortens lifespan by 7.5 yrs

• 3. Lifestyle Choices:

– Smoking: lost 6-10 yrs

– Overweight: 6 yrs

– Driving: 7 months

– Alcohol: 5 months

• Biological Hazards

• Infectious disease: caused when pathogen invades

body & multiplies (either directly or through vector)

– Ex: flu, malaria, measles

– Can be Transmissible

• Non-transmissible disease: not caused by organism

& not spread – Ex: heart disease, some cancers, diabetes, etc.

Biological Hazards

• Infectious diseases spread through air, water, food,

bodily fluids (blood, mucus)

• Since 1950, infectious diseases have declined due to:

– Better healthcare & sanitation

– Antibiotics & vaccines

• Still have problems, esp. in developing countries:

– Epidemics: large-scale outbreak of infectious disease in an

area or country

– Pandemic: global epidemic

Biological Hazards: Current Issues

• Tuberculosis (TB) – bacterial infection in lungs

» 1 in 3 have bacteria

» Kills 1.8 mil per year

» Problem: Genetic resistance! Multi-drug resistant TB getting more common

–Biggest viral killer… Influenza

• AIDS: Acquired immune deficiency syndrome, caused by human immunodeficiency virus (HIV) – HIV destroys immune systems & makes people vulnerable to

infections

– Identified in 1981; now >33 mil people have it – most in Africa

– Infects 2.5 mil per year; kills 2 mil per year

– With antiviral costing >$25,000 per year, can expect to live another 24 years

3. Hepatitis B virus (HBV): damages liver; transmitted through sex, needles

• Emergent Diseases: newly discovered – West Nile Virus

– Avian Flu

• Malaria

– Caused by protozoan parasite (Plasmodium), spread through Anopheles mosquitoes

» Destroys RBCs, causing fever, pain, vomiting, & death

– Problem: mosquitoes resistance to insecticide & Plasmodium resistance to antimalarial drugs

– Solutions:

» Genetically-engineered mosquitoes

» Mosquito nets

Biological Hazards

• Antibiotic resistance: Genetic resistance occurs through natural

selection

– Causes: Over-prescribed/ over-used, Use in livestock

production, Anti-bacterial soap/hand sanitizer could be

creating “stronger” bacteria

– Methicillin-resistant staphylococcus aureus (MRSA)

Chemical Hazards Toxic chemical: substance that when inhaled, ingested, or absorbed can

cause temporary or permanent harm or death to humans and animals

Top 5 according to EPA:

1. Arsenic

2. Lead

3. Mercury

4. Vinyl chloride

5. Polychlorinated biphenyls (PCBs)

Three major types of toxic chemicals:

1. Carcinogens: chemicals, radiation, or viruses that cause cancer Ex: arsenic, benzene, formaldehyde, PCBs, UV radiation

2. Mutagens: chemicals or radiation that cause or increase frequency of mutations in DNA

3. Teratogens: chemicals that cause harm or birth defect to fetus Ex: alcohol, PCBs, lead, mercury

Focus on Polychlorinated biphenyls (PCBs): class of 200 chlorine-containing organic compounds

– Used as lubricants, insulators, paints, pesticides, etc.

» Banned in 1977

– Problem: long persistence and biomagnify (fat-soluble)

» ~70% of all PCBs made in US still in environment

• Neurotoxins: harm nervous system:

– Ex: PCBs, arsenic, lead, some pesticides,

methylmercury

– Effects: learning disabilities, ADD, Parkinson’s, etc.

• Hormonal Disrupters:

– Some pesticides & synthetic chemicals have same molecular

shape as hormones (called Hormonally Active Agents/

HAAs)

– Ex: aluminum, Atrazine, DDT, PCBs, mercury, BPA

– Gender benders: estrogen mimics & hormone blockers that

affect sexual development & reproduction

– Thyroid disrupters cause growth & weight problems

• Hormonally-Active Agents:

– BPA: bisphenol A

» A estrogen mimic used in hard plastics (esp. food containers,

bottles, etc.)

» Leaches into food & drink, even when not heated

» Effects: brain damage, early puberty, breast cancer, obesity,

liver damage, impaired immune function, etc.

– Phthalates:

» In PVC bottles & solvents (perfume, lotions, shampoos, etc.)

» Banned in EU and 14 other countries

» Associated with birth defects, liver & kidney damage, immune

problems etc.

• Toxicology study of harmful effects of chemicals on

humans & other organisms

• Toxicity: how harmful something is. Depends on:

»Dose: amount exposed to

»Frequency

»Genetic make up of those exposed

»Health of those exposed

Other factors include:

Solubility (water or fat)

Persistence

Biomagnification (build up through food chain)

Chemical interactions (antagonistic or synergistic)

Response: the damage to health resulting from exposure to a toxin

» Acute effects: immediate effect of exposure

» Chronic effects: long-lasting effects from one or repeated exposures

• Determining Toxicity

– Expose a population of lab animals to measured doses under controlled conditions

– Create a dose-response curve: determine effects at various doses

– Lethal Dose (LD50): dose that can kill 50% of the animals in a test pop within certain time period

Lower the LD50 number =

more toxic the

chemical (Units: mg/kg)

Poison = any substance that

has an LD50 of 50 mg or

less per kg of body weight

• Threshold dose-response curve: a

threshold dose must be reached

before any detectable harmful

effects occur.

2 Types of Dose-Response Curves:

Nonthreshold dose-response curve:

any dosage of a toxic substance causes

harm that increases with the dosage.

The smallest amount of the

dosage has a harmful effect

Human Health

Are trace levels harmful? We don’t know

Prevention

In 2000, POPs Treaty: ban or phase out dirty

dozen - 12 most persistent pollutants detrimental

to life:

DDT & 8 other pesticides

PCBs

POPs treaty went into effect in 2004, not yet ratified by

U.S.

In 2007, European Union enacted REACH

(registration, evaluation, and authorization of

chemicals)