The Human Population
Objectives:
1. Describe global population trends.
2. Understand age-structure diagrams and use the diagrams to make predictions about
future population dynamics.
3. Describe the differences in population changes and age structures between developing
and developed countries.
4. Explain how human population and development may cause environmental harm.
Population
All members of the same species that live in the same place at the same time and breed with
each other.
Properties of a population
1. Size: total # of individuals
2. Density: # of individuals per unit area or volume.
3. Dispersion: arrangement of its individuals in space (eve, clumped or random)
A population gains individuals with each new off spring or birth and loses them with each
death. The resulting population change over time can be represented by the equation below.
The percentage change in size of a population over a given period of time is that population’s
growth rate. The growth rate is the birth rate minus the death rate.
Change in
population
size
=
Births
-
Deaths
Growth rate can be described as:
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Positive
Negative
Zero
Biotic Potential
A species fastest rate at which its population can grow, this will be limited by the reproductive
potential.
Reproductive Potential
Maximum number of offspring that each member of a population produces.
Exponential Growth
Means populations grow faster and faster. It occurs in nature only when populations have
plenty of food, space and have little or no competition or predators.
What limits a population?
-
Carrying Capacity
1. Is the population size where birth rates and death rates are equal.
2. The maximum population size of the species that the environment can sustain
indefinitely.
-
Competition within a population
Members of a population often compete with each other.
-
Resources limits
Patterns of Population Change
1. Density-Dependent Change: regulate the growth of a population depending on its
density.
2. Density-Independent Change: regulate population growth without depending on its
density.
Mark and Recapture Lab
Sometimes it is not possible to count each individual in a population. The organism you want
to count might be very mobile, or the population might be so large or occupy such a big area
that counting each individual would take too much time and money. In this case, there are
some methods we can use to estimate the population. One method is the mark and recapture
method.
The basic idea is that you capture a small number of individuals of a population, put a harmless
mark on them, and release them back into the population. At a later date, you catch another
small group, and record how many have a mark. In a small population, you are more likely to
recapture marked individuals, whereas in a large population, you are less likely. This can be
expressed mathematically using the equation below.
Lincoln-Peterson Index:
N = M x S/R
N = estimated Number of individuals in the population
M = number of individuals captured and Marked
C = total number Captured the second time (with and without a mark)
R= number of individuals Recaptured (those with a mark)
Carrying Capacity (K)
Refers to the number of individuals of a population that can be sustained indefinitely by a
given area.
Malthusian Theory
According to this theory, three factors would control human population:
1. War
2. Famine
3. Disease
Malthus called them the “Positive Check” increase mortality rate and reduce life expectancy.
These are countered by “Preventative Checks”
1. Celibacy
2. Birth control
Reduces fertility rates.
Zero population Growth
Paul Ehrlich states the following:
“It’s the environment, not specifically the food supply.”
His ideas suggest that the human population is moving rapidly toward complete environmental
collapse.
(Birth + Immigration) – (Death + Emigration) = 0
A cornucopian is someone who believes that continued progress and provision of material
items for mankind can be met by advances in technology.
How species interact with each other
A niche can bethe range of conditions in which a species can survive.
Population Numbers
Currently 7.2 billion people on Earth
Developing World: 6 billion
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Lower levels of development
Lower levels of household income
Low levels of infrastructure
Low medical development
Population growth continues to increase
Developed World: 1.2 billion
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High level of infrastructure
Financial
Technological
Medical development
Household income
Population growth is stable or slight decline
Demographic Basics
Demographers
Are researchers who study population and its changes.
Terms used by demographers:
Birth rate
Commonly referred to as the crude birth rate, this is the number of births per 1,000
people within a certain population during a given year.
Death rate
Commonly referred to as the crude death rate, this is the number of deaths per 1,000
people within a certain population during a given year.
Replacement-level fertility
This is the average number of births couples in a population must have in order to
keep the population stable at a certain number.
Developed countries: 2.1 children per woman
Developing countries: higher than 2.1 children per woman
Total fertility rate
This is the average number of children a woman in a population has in her lifetime.
*excluding immigration and emigration* if total fertility rate exceeds replacementlevel fertility.
If the total fertility rate is below the replacement-level fertility.
Determining in Percentage Terms how Fast a Population is
Growing or Declining
Annual rate of population change (%) = Birth rate – Death rate / 10
Doubling Time and the Rule of 70
The time it takes for a population to double in size can be estimated from the “Rule of 70”
Doubling time rule = 70 / annual growth rate
1. The estimate of the average number of children that each woman in a population will
have throughout her lifetime is referred to as: total fertility rate
2. The rule of 70 is used to calculate the: doubling time
How and Why Populations Change
Age-Structure Diagrams
It describes how its members are distributed across age ranges.
There are three broad categories for organizing age-structure diagrams:
1. Rapid growth (developing worlds)
2. Slow growth (developed worlds)
3. Decline in growth (developed words)
Demographic transition theory: the theory of demographic transition says that, as a country
moves from a subsistence economy to industrialization and increased wealth, it undergoes a
predictable shift in population growth.
Phases of Demographic Transition
Phase one: preindustrial - population is stable, with both high birth rates and high death
rates. The death rates are high because there is increased disease, minimal medical care, poor
sanitation, and limited food supplies. High death rate, people tend to produce more offspring
to try to compensate for the mortality.
Phase two: industrial - increased access to food and goods. Access to healthcare, clean
drinking water, death rates decline and birth rate is higher.
Phase three: stabilization - increased access to food and goods, access to healthcare, better
sanitation, clean drinking water, death rates declines, birth rates declines. Birth rate is
declining because people are taking more time for education and they have more access to
birth control.
Phase four: pop. Decline - high levels of affluence, high economic development, fewer young
people, higher proportion of elderly people. What problems can this lead? Creativity will
decrease because young people decline
Unit IV
Land Use
Section 1: How We Use Land
Land Use and Land Cover
There are different types of land cover and different human uses for each cover type.
What are land covers?
It is what you find on a patch of land
LAND COVER TYPE
RANGELAND
FOREST LAND
CROPLAND
PARKS AND PRESERVES
WETLANDS, MOUNTAINS, DESERS, AND
OTHERS
URBAN LAND
HUMAN USE OF LAND
Land used to graze livestock and wildlife
Land used for harvesting wood, wildlife, fish,
nuts, and other resources
Land used to grow plants for food and fiber
Land for recreation
Land that is difficult to use for human
purposes
Land used for houses, businesses, industry,
and roads
Ecosystem services are the resources that are produced by natural and artificial ecosystems.
Rural areas provide (independent)
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Clean water
Fertile soil
Land
Crops
Trees
Wood
Paper
And most of the O2
EXAMPLES OF ECOSYSTEM SERVICES
PURIFICATION OF AIR AND WATER
PRESERVATION OF SOIL AND RENEWAL OF SOIL FERTILITY
PREVENTION OF FLOOD AND DROUGHT
REGULATION OF CLIMATE
MAINTENANCE OF BIODIVERSITY
MOVEMENT AND CYCLING OF NUTRIENTS
DETOXIFICATION AND DECOMPOSITION OF WASTES
Section 2: Urban Land Use
Urbanization
The movement of people from rural areas to towns or cities is called urbanization.
People move towards (Rural)
1.
2.
3.
4.
5.
6.
7.
Needs
Wants
Jobs
Education
Safety
Recreational areas
Opportunity
(Urban)
Urban crisis
When urban areas grow too rapidly it causes:
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Overwhelming infrastructure
Traffic jams
Substandard housing
Air and water pollution
What is infrastructure?
All things that society builds.
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Roads
Sewers
Railroads
Bridges
Canals
Fire and police stations
Schools
Libraries
Hospitals
Water mains
Power lines
Urban sprawl:
Rapid expansion of a city into the countryside around the city
-
Suburbs, which are generally built on land that was used for food production.
Substandard housing.
Critical Thinking
1. Designer Andrea Tyson, a conservation planner from Naples, Florida, calls Arendt’s
approach “capitalism mated with conservation.” Explain why you think she would
use this term.
It works for everybody. The landholder doesn't lose because the land doesn't get
ripped away. He gets paid for credits that are used in an area that allows for more
density. The developer gets his value because he is allowed to get higher density.
And this is all at the cost of growth, not at the cost of the tax payer.
2. Some communities are enacting laws that require a certain percentage of land in
new developments to be conserved. Do you think this is a good idea? Why or why
not?
Yes, because more land is going to be protected in the long run.
Air Pollution
What is Air?
Air is considered to be a mix of gases in the atmosphere.
Air Quality
Pollutants are natural or human made compounds that in some ways it harms or changes the
natural processes of the atmosphere.
Problems with Air Quality
When did air pollution begin?
Early People
Burning wood for heat and carbon

Followed
Industrial Revolution
Burning of coal
Photochemical Smog
Photochemical smog is the smog produced by the reaction between more than 100 different
compounds.
How does it take place?
The abundance of car and sunshine provides the perfect setting for these chemical reactions to
take place.
The Clean Air Act
The Clean Air Act was approved in 1970, and it regulates 189 pollutants. The five most
important pollutants are:
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O3
Sulfur Dioxide
Nitrogen Dioxide
Carbon Monoxide
Lead
What is the result of the Clean Air Act?
In short, the air in the United States is much cleaner. Visibility is better and people are no
longer incapacitated by industrial smog. However, despite the Act, industry, power plants and
vehicles put 160 million tons of pollutants into the air each year.
Regional Air Quality
Solving Problem
1. If City A is a heavy producer of pollutants, and City B is a city clean of heavy
industrial activity, how will City B be affected by City A? City A’s pollution will spread
to City B by wind currents, which will result in the pollution of that city.
2. If Alfa City was a city built on Plain lands, with heavy industrial activity, and Beta City
a city built on Mountain ranges. How will Beta City be affected by Alpha City? The air
pollutants produced by Alpha City will rise in altitude, probably contaminating Beta
City.
Air quality factors that influence in Air Pollution:
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Geographical Region (mountain range, winds, inversions)
Released pollutants
Types of Air Pollution
Air pollution can be classified in:
1. Primary Pollutants
Which enter the atmosphere
2. Secondary Pollutants
When primary pollutants react with other primary pollutants.
Primary Pollutants
Some primary pollutants are natural, such as volcanic ash. Dust is natural but exacerbated by
human activities; for example, when the ground is torn up for agriculture or development.
Most primary pollutants are the result of human activities, the direct emissions from vehicles
and smokestacks.
Primary pollutants include:
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CO
CO2
NO2
SO2
Ash
Dust
Fecal matter
Lead
Volatile organic compounds
PRIMARY AIR POLLUTANTS
POLLUTANT
DESCRIPTION
PRIMARY SOURCES
Carbon
CO is an odorless,
Sources of CO are cars,
Monoxide (CO) colorless, poisonous
trucks, buses, small
gas. It is produced by
engines, and some
the incomplete
industrial processes.
burning of fossil fuels.
Nitrogen
When combustion
NOx comes from burning
Oxides (NOx)
(burning)
fuels in vehicles, power
temperatures exceed
plants, and industrial
538C, nitrogen and
boilers.
oxygen combine to
form nitrogen oxides.
Sulfur Dioxide
(SO2)
SO2 is produced by
chemical interactions
between sulfur and
oxygen.
SO2 comes mostly from
burning fossil fuels.
Volatile
Organic
Compounds
(VOCs)
Particulate
Matter
(particulates
or PM)
VOCs are organic
chemicals that
vaporize readily and
form toxic fumes.
Particulates are tiny
particles of liquid or
solid matter.
VOCs come from burning
fuels. Vehicles are a
major source of VOCs.
Most particulates come
from construction,
agriculture, forestry, and
fires. Vehicles and
industrial processes also
contribute particulates.
EFFECTS
CO interferes with the blood’s
ability to carry oxygen, slowing
reflexes and causing drowsiness.
In high concentrations, CO can
cause death.
NOx can make the body
vulnerable to respiratory
infections, lung diseases, and
cancer. NOx contributes to the
brownish haze seen over cities
and to acid precipitation.
SO2 contributes to acid
precipitation as sulfuric acid.
Secondary pollutants that result
from reactions with SO2 can harm
plant life and irritate the
respiratory systems of humans.
VOCs contribute to smog
formation and can cause serious
health problems, such as cancer.
They may also harm plants.
Particulates can form clouds that
reduce visibility and cause a
variety of respiratory problems.
Particulates have also been linked
to cancer. As well, they may
corrode metals and erode
buildings and sculptures.
Secondary Pollutants
Any city can have photochemical smog, but it is most common in sunny, dry locations.
1. Photochemical smog forms when cars release Nitrogen Dioxide (NO2)
2. NO2 splits (sun’s energy) and releases an Oxygen Ion (O)
3. The O then combines with oxygen molecules (O2) to form 03 (ozone)
Causes of Air Pollution
Short-Term Effects of Air Pollution on Health
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Headache
Nausea
Irritation to the eyes, nose, and throat
Tightness in the chest
Coughing
Upper respiratory infections (Bronchitis and pneumonia)
Worsen asthma and emphysema
Long-Term Effects of Air Pollution on Health
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Emphysema
Lung cancer
Heart disease
Worsen other conditions
Radon Gas
Colorless, tasteless, odorless, and radioactive gas. Radon comes from decay of Uranium.
Consequences
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Destroys the genetic material (when inhaled)
Cause cancer
Asbestos
Minerals that form in long, thin fibers.
Use of Asbestos
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Insulator
Fire retardant
Building materials
Consequences
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Cut and scar the lung
Cause a disease called: asbestosis
Acid Rain
They are the result of the acidification of rain caused by pollutants.
Effects of Acid Rain
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Denaturalizes minerals
Denaturalized AA
Denaturalizes metals
Inhabitable water
Water Pollution
Its defined as the contamination of a certain body of water caused by chemical, physical, or
biological agents.
Water pollution comes from two types of sources:
Point-Source Pollution
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A single source of pollution, identifiable
Examples:
Leaking oil tanker
Polluted water from abandoned and active mines
Nonpoint-Source Pollution
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Come from many different sources that are difficult to identify
Examples:
Chemicals added to road
Pesticides, herbicides
Precipitation containing air pollutants
Main source pollutants:
Municipal Pollution
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Wastewater from cities and towns
Sewage disposal
Storm drains
Septic tanks (sewage from houses)
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Boats
Yard runoff
Agricultural Pollution
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Wastewater from farmlands
Runoff from crops
Livestock
Fertilizers
Pesticides
Animal wastes (nearby waterway)
Industrial Pollution
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Wastewater from factories and hospitals
Radioactive substances
Heavy metals, oils
Chemicals (sulfur, FF)
Petroleum
Heated water
Principal Water Pollutants
TYPE OF POLLUTANT
Pathogens
Organic Matter
Organic Chemicals
Inorganic Chemicals
Heavy Metals
AGENT
Disease-causing organism,
such as bacteria, viruses,
protozoa, and parasitic
worms.
Feces, food wastes
Pesticides, fertilizers,
plastics, detergents
Acids, bases, salts
Lead, mercury, cadmium,
and arsenic
MAJOR SOURCE
Nonpoint source
Point and Nonpoint
Wastewater and Treating System
Wastewater is the water that contains wastes from homes or industry.
Primary Treatment
1) Filtration: wastewater is passed though a large screen to remove solid objects.
2) First Settling Tank: wastewater is sent into a large tank, where smaller particles sink.
Secondary Treatment
3) Aeration Tank: wastewater is mixed with oxygen and bacteria (bacteria feed on
wastes)
4) Second Settling Tank: bacteria grown in the aeration tank, as well as other solids
wastes are removed.
5) Chlorination: chlorine is added to disinfect the water, then it is released in a stream,
lake or ocean.
Thermal Pollution
Dissolved oxygen (DO) is directly related to temperature. The higher the temperature the
lower the DO.
Groundwater Pollution
When polluted surface water percolates down from the Earth’s surface.
Common groundwater pollutants:
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Pesticides
Herbicides
Chemical fertilizers
Petroleum products
Solid Waste
Its defined as any discarded solid material
Where does your trash go?
Big problem
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Amount
Space
Type of solid
NIMBY Phenomenon (Not in My Backyard)
a) Why are landfills considered to be undesirable?
Landfills usually have a repugnant smell and are breeding grounds for many pathogens
and pests.
b) What would happen if everyone took the NIMBY point of view?
There would be no space for landfills.
There are two main types of solid wastes
Biodegradable
They are material that can be broken down by biological processes:
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Newspaper
Paper bags
Cotton fiber
Leather
Nonbiodegradable
They are materials that cannot be broken down in biological processes:
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Polyester
Polymers
TYPES OF SOLID WASTE
Municipal Waste
Manufacturing Waste
Mining Waste
MUNICIPAL SOLID WASTE (PERCENTAGE BY
WEIGHT)
12%
11%
38%
11%
8%
3%
5%
Yard Waste
Food Waste
Plastics
5%
Metals
7%
Rubber
Glass
Materials best for recycling
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Paper
Metal
Glass
Landfill
Problems with Landfills
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Leachate: mixture of water and dissolved chemicals
Methane
Wood
Other
Paper
Safeguarding Landfills
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Leachate monitor
Vent pipes for Methane
Building More Landfills
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No space
1988: there was a total of 8,000 landfills in the US
2005: there is a total of 1,700 landfills in the US
Incinerators
Positive Impact
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Reduces the amount of solid waste sent to landfills
Reduces the weight of a solid waste by 75%
Take up less space in landfills
Negative Impact
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They release poisonous gases
Contributes to Acid Rains
They release small amounts of toxic heavy metals into the air
Impact on human health
Source Reduction
Change in design, manufacture, purchase, or use of material to reduce the amount of toxicity.
Reusing materials
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Rechargeable batteries
Refillable bottles
Reducing Waste

Redesigning products (less material)
Recycling
Is the process of reusing materials or recovering valuable materials from waste or scrap.
Did you know?
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95% of less energy to produce aluminum from recycled aluminum than from ore.
70% of less energy is needed to make paper from recycled paper than from trees.
Recycling Cycle
Step 1. Collecting and sorting discarded materials by type.
Step 2. Taking the materials to a recycling facility.
Step 3. Cleaning the discarded materials so that they can be shredded or crushed.
Step 4. Reusing the shredded materials to manufacture new products.
Classifications of plastics:
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Type 1 & 2: commonly recycled
Type 4: less commonly recycled
Type 3, 5, 6, & 7: not recycled
Classwork #1
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Explain what makes a material biodegradable.
When it is made from natural materials, and can be broken down by biological
processes.
Describe how a modern landfill works. List two environmental problems that can be
caused by landfills. Explain your answer.
A landfill works using microorganisms to decompose biodegradable solid waste. Solid
waste is dumped into the landfill, then soil is spread over the trash. All biodegradable
solid waste will be decomposed by microorganisms in the soil. During decomposition,
methane gases are released. These gases are flammable, and must be vented from the
landfill. Another product of decomposition is liquid goo called leachate.
Describe one advantage and one disadvantage of incinerating solid waste.
It makes waste about 75% lighter. But the waste becomes more toxic when burned.
Name two nonbiodegradable products that you use. What makes them
nonbiodegradable? Name biodegradable products that you can use instead.
Plastic bags and plastic bottle. They are nonbiodegradable because they are made
from synthetic products. I can instead use paper bags and metal thermoses.
Explain what you can do to help reduce the amount of solid waste that you throw
away and to reduce what is thrown away in your community.
Reuse boxes and bags, wash and reuse plastic containers, use reusable containers,
take my own bag to the supermarket, give food scraps to animals, etc.
Compost
A dark brown, crumbly material that is spread on gardens and fields to enrich the soil.
BENEFITS OF COMPOSTING
Keeps organic wastes out of landfills
Provides nutrients to the soil
Increases beneficial soil organisms, such as worms and centipedes
Suppresses some plant diseases
Reduces the need for fertilizers and pesticides
Types of degradable plastics
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Photodegradable plastic
Green plastic (blend of plant sugars with plastic)
Problems with degradable plastics
Smaller pieces of plastic can affect smaller organisms.
Classwork #2
1.
2.
3.
4.
5.
6.
Name three things you could do each day to produce less waste.
Use reusable bottles
Reuse plastic bags
Use paper bags instead of plastic ones
Explain how buying certain products can help reduce solid waste.
Not buying individually packaged goods prevents excessive waste.
Describe the steps it takes to recycle a piece of plastic.
Sort, clean, shred, reuse shredded materials.
List two benefits of composting.
Provides nutrients to the soil
Suppresses some plant diseases
What are the advantages and disadvantages to producing degradable plastics?
Degradable plastics break down faster but become microplastics that harm organisms.
Decide which type of bag you would choose the next time you go shopping. Explain
why you made this choice. What are other uses of the bag you chose?
Plastic bag, it’s good for later trash disposal.
Hazardous Waste
They are the leftovers of chemicals used to generate other compounds.
Types of Hazardous Waste
Solid: PBC, Toxic Metals, Lead, Zinc, Radioactive Waste
Liquid: Solvents, Mercury, lubricant
Gas: Pesticides.
Food and Agriculture
Section 1
What is the difference between hunger and famine?
Feeding the World
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Famine is the widespread malnutrition and starvation in an area due to a shortage of
food, usually caused by a catastrophic event.
Modern agriculture practices provide most of the world’s population with enough food
to survive.
However, some of these practices can cause environmental damage that eventually
makes growing food crops more difficult.
Famine
“At least 1 in 5 households now faces an extreme lack of food, more than 30 percent of the
population is suffering from acute malnutrition, and at least two people out of every 10,000
are dying each day”
Solutions
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The world food program
Food aid
What are some causes of famine?
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Drought
Flooding
Unseasonable cold
Insect infestations
Plant diseases
Armed conflict
Poor distribution of existing food supplies
Humans and Nutrition
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The human body uses food both as a source of energy and as a source of materials for
building and maintaining body tissues.
The amount of energy that is available in food is expressed in Calories. One calorie is
equal to 1,000 calories or one kilocalorie.
The major nutrients we get from food and carbohydrates, proteins, and lipids. Our
bodies need smaller amounts of vitamins and minerals to remain healthy.
Malnutrition is a disorder of nutrition that results when a person does not consume
enough of each of the body nutrients that are needed by the human body.
There are many forms of malnutrition. For example, humans need to get 8 essential
amino acids from proteins. This is easily done if a variety of foods is eaten. However, in
some parts of the worlds the only sources of food may be corn and rice, which contain
protein, but lacks one of the essential amino acids. Amino acid deficiency can result
from such a limited diet.
Sources of Nutrition
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Diet is the type of amount of food that a person eats. A healthy diet is one that
maintains a balance of the right amount of nutrients, minerals, and vitamins.
The foods produced in the greatest amounts worldwide and grains, plants of the grass
family whose seed are rich in carbohydrates.
Besides eating grains, most people eat fruits, vegetables, and smaller amount of
meats, nuts and other foods that are rich in fats and proteins.
Diets Around the World
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People worldwide generally consume the same major nutrients and eat the same basic
kinds of food. But diets vary by region
People in more developed countries tend to eat more food and a larger proportion of
proteins and fats and people in less developed countries.
The Ecology of Food
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As the human population grows, farmland replaces forests and grasslands.
Feeding everyone while maintaining natural ecosystems becomes increasingly difficult.

Different kinds of agriculture have different environmental impacts and different levels
of efficiency.
Food Efficiency
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The efficiency of a given type of agriculture is a measure of que quantity of food
produced on a given area of land with limited inputs of energy and resources.
An ideal food crop is one that efficiently produces a large amount of food with little
negative impact on the environment.
Thus, a given area of land can usually produce mote food for humans when it is used
to grow plants as when it’s used to raise animals.
Old and New Foods

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Yield is the number of crops produced per unit area
Some organisms have been a source of food for centuries, while other sources are just
being discovered.
World Food Problems
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Some people become malnourished because they simply do not get enough food
More food is needed each year to feed the world growing population
World food production has been increasing for decades but now food production is
not increasing as fast as the human population.
Unequal Distribution
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If all the food in the world today were divided equally among the human population,
no one would have quite enough food for good health.
But food is not divided equally, and malnutrition is largely the result of poverty. Even
in the United States, many poor people suffer from malnutrition.
Droughts and Famines
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A drought is a prolonged period during which rainfall is below average, and crops
grown without irrigation may produce low yields or fail entirely.
A drought is more likely to cause famine in places where most food is grown locally
If a drought occurs, there may be no seed to plant crops the following year. The effects
of a drought can continue for years.
Section 2
The Green Revolution
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Occurred during the 1950s and 1960s
Resulted in the adoption of new technologies, including
o High yielding varieties of cereals
o New methods of cultivation of cereals
o Distribution of hybridized seeds, synthetic fertilizers, and pesticides
Greatly increased amount of food that could be grown on the same amount of land
Pros
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May have decreased food insecurity
Reduces need to expand into new, uncultivated land
Created more predictable and consistent harvests
Reduced food prices
Cons
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Reduced agricultural biodiversity
Many new varieties require large amounts of fertilizers, pesticides, and water
The products needed can be expensive for farmers
Effects of Malnutrition
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45% of all childhood deaths are related to malnutrition
Increased vulnerability to diseases
Developmental delays
Stunted growth
Crops and Soil
Imagine you are a farmer. What factors would you have to consider when choosing which crops
to plant?
 Temperature
 Growing season
 Altitude
 Rainfall
 Wind
 Soil
 Slope
Agricultural land is land that can be used to grow crops. Earth has only a limited area of
agricultural land. But, as the human population continues to grow, the amount of agricultural
land per person decreases.
Agriculture: Traditional
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The basic processes of farming include, plowing, fertilization, irrigation, and pest
control.
Traditionally, plows are pushed by the farmers or pulled by livestock. Plowing helps
crops grow by mixing soil nutrients, loosening soil particles, and uprooting weeds.
Organic fertilizers, such as manure, are used to enrich soil. While fields are irrigated by
water flowing through ditches.
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These traditional techniques have been used since the earliest days of farming.
Agriculture: Modern
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In most industrialized countries, the basic processes of farming are now carried out
using modern agricultural methods.
Machinery powered by fossil fuels is now used to plow the soil and harvest crops.
Synthetic chemical fertilizers have replaced manure and plant wastes to fertilize soil.
A variety of overhead sprinklers and drip systems may be used for irrigation. And
synthetic chemicals are used to kill pests.
Organic vs. Chemical Fertilizers
Inorganic Fertilizers
o
o
Nutrients readily available
May have to fertilize multiple times
Organic Fertilizers
o
o
o
o
o
o
Manures, compost, bone meal
Low concentrations of plant nutrients
Nutrients must be converted to inorganic forms
Add structure to the soil
Feed beneficial microbes
Higher cost
Fertile Soil: The Living Earth
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Soil that can support the growth of healthy plants is called fertile soil.
Topsoil is the surface layer of the soil, which is usually richer in organic matter than the
subsoil is.
Fertile topsoil is composed of living organisms, rock particles, water, air, and organic
matter, such as dead or decomposing organisms. Several layers of soil lie under the
topsoil. The bottom layer is bedrock, which is the solid rock from which most soil
originally forms.
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Most soil forms when rock is broken down into smaller and smaller fragments by wind,
water, and chemical weathering. Chemical weathering happens when the minerals in
rock react chemically with substances to form new materials. Temperature changes
and moisture can also cause rock to crack and break apart.
It can take hundreds or even thousands of years for these geological processes to form
a few centimeters of soil.
Biological Weathering
One example of microbial activity is lichen; lichen is fungi and algae, living together in a
symbiotic relationship. Fungi release chemicals that break down rock minerals; the minerals
thus released from rock are consumed by the algae.
Chemical Weathering
Weakening and disintegration by oxidation, hydrolysis, and carbonation. Chemical weathering
of rock minerals generally occurs more quickly in hot, humid climatic regions.
Physical Weathering
Temperate fluctuation, abrasion, frost action (freezing and thawing), and salt crystal growth.
Fertile Soil: The Living Earth
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Other processes also help to produce fertile topsoil. For example, the rock particles
supply mineral nutrients to the soil.
Fungi and bacteria live in the soil, and they decompose dead plants as well as organic
debris and add more nutrients to the soil.
Earthworms, insects, and other small animals help plants grow by breaking up the soil
and allowing air and water into it.
Soil Erosion: A Global Problem
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Erosion is a process in which the materials of the Earth’s surface are loosened,
dissolved, or worn away and transported from one place to another by a natural
agent, such as wind, water, ice, or gravity.
Without topsoil, crops cannot be grown. Yet, almost all farming methods increase the
rate of soil erosion.
Tillage breaks the soil surface into small pieces.
o Influences wind erosion by dehydrating the land.
Deforestation also increases erosion.
o Trees help hold soil in place.
Overgrazing removes ground cover.
Land Degradation
Land degradation happens when human activity or natural processes damage the land so that
it can no longer support the local ecosystem. In areas with dry climates, desertification can
occur.
Desertification is the process by which human activities or climatic changes make arid or
semiarid areas more desert like. This process is causing some of our arable land to disappear.
Soil Conservation
There are many ways of protecting and managing topsoil and reducing erosion. Soil usually
erodes downhill, and many soil conservation methods are designed to prevent downhill
erosion.
An even more effective method of plowing is leaving strips of vegetation across the hillside
instead of plowing the entire slope. These strips catch soil and water that run down the hill.
Still, many areas of land that have hills are not suited to farming, but may be better used as
forest or grazing land.
In no-till farming, a crop is harvested without turning the soil over, as in traditional farming.
Later, the seeds of the next crop are planted among the remains of the previous crop. The
remains of the first crop hold the soil in place while the new crop develops. Although this
method saves time and reduces soil erosion, it is not suited for all crops. Other disadvantages
include soil that is too densely packed and lower crop yields over time.
Enriching the Soil
Soil was traditionally fertilized by adding organic matter that would decompose, adding
nutrients to the soil and improving the soil texture. However, inorganic fertilizers that contain
nitrogen, phosphorus, and potassium have changed farming methods. Without them, world
food production would be less than half of what it is today. If erosion occurs in areas fertilized
with inorganic materials, waterways may become polluted. Over the past 50 years, the use of
such inorganic fertilizers has increased rapidly.
A modern method of enhancing the soil is to use both organic and inorganic materials by
adding compost and chemical fertilizers to the soil. Compost is a mixture of decomposing
organic matter, such as manure and rotting plants, that is used as fertilizer and soil
conditioner. Many cities and industries now compost yard and crop wastes. This compost is
then sold to farmers and gardeners, and the process is saving costly land fill space.
Salinization
The accumulation of salts in the soil is known as salinization. Salinization is a major problem in
places that have low rainfall and naturally salty soil. When water evaporates from irrigated
land, salts are left behind. Salinization can be slowed if irrigation canals are lined to prevent
water from seeping into the soil, or if the soil is watered heavily to wash out salts.
Pest Control
Worldwide, pests destroy about one-third of the world’s potential food harvest. A pest is any
organism that occurs where it is not wanted or that occurs in large enough numbers to cause
economic damage. Humans try to control populations of many types of pests, including plants,
fungi, insects, and microorganisms.
Pesticides
Many farmers rely on pesticides to produce their crops. A pesticide is a poison used to destroy
pests, such as insects, rodents, or weeds; examples include insecticides, rodenticides, and
herbicides. Pesticides, however, can also harm beneficial plants and insects, wildlife, and even
people.
Pesticide Resistance
Over time, spraying large amounts of pesticide to get rid of pests usually makes the pest
problem worse. Pest populations may evolve resistance, the ability to survive exposure to a
particular pesticide. More than 500 species of insects have developed resistance to pesticides
since the 1940s.
Human Health Concerns
Pesticides are designed to kill organisms, so they may also be dangerous to humans. Cancer
rates among children in areas where large amounts of pesticides are used on crops are
sometimes higher than the national average. People who apply pesticides need to follow
safety guidelines to protect themselves from contact with these chemicals.
Pollution and Persistence
The problem of pesticides harming people and other organisms is especially serious with
pesticides that are persistent. A pesticide is persistent if it does not break down easily or
quickly in the environment. Persistent pesticides do not break down into harmless chemicals,
and they accumulate in the water and soil. Some pesticides have been banned in the US for
decades but can still be detected in the environment.
Biological Pest Control
Biological pest control is the use of certain organisms by humans to eliminate or control pests.
Every pest has enemies in the wild, and these enemies can sometimes be used to control pest
populations. Biological pest control includes the use of:
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Pathogens
Plant defenses
Chemicals from plants
Disruption of insect breeding
Integrated Pest Management
Integrated pest management is a modern method of controlling pests on crops. The goal of
integrated pest management is not to eliminate pest populations but to reduce pest damage
to a level that causes minimal economic damage. Such programs can include a mix of farming
methods, biological pest control, and chemical pest control.
Biological methods are the first methods used to control the pest. So, natural predators,
pathogens, and parasites of the pest may be introduced. Cultivation controls, such as
vacuuming insects off the plants, can also be used. As a last resort, small amounts of
insecticides may be used. These insecticides are changed over time to reduce the ability of
pests to evolve resistance.
Engineering a Better Crop
Genetic engineering is a technology in which the genome of a living cell is modified for medical
or industrial use. Scientists may use genetic engineering to transfer desirable traits, such as
resistance to certain pests, from one organism to another. Plants that result from genetic
engineering are called genetically modified (GM) plants.
Sustainable Agriculture
Farming that conserves natural resources and helps keep the land productive indefinitely is
called sutainable agriculture. It involves planting productive, pest-resistant crop varieties that
require little energy, pesticides, fertilizer, and water.
Section 3
Animals and Agriculture
Food from animals has been the basis of life for some human populations for centuries. Our
ancestors obtained animal protein by hunting and fishing. Today, most people get animal
protein from domesticated species. Domesticated describes organisms that have been bred
and managed for human use.
Food from Water
Because fish are an important food source for humans, the harvesting of fish has become an
important industry worldwide. However, when too many fish are harvested over a long period
of time, ecological systems can be damaged.
Overharvesting
Overharvesting is the catching or removing from a population more organisms than the
population can replace. Many governments are now trying to stop overharvesting. They have
created no-fishing zones, so that fish populations can recover.
Global Fisheries Crisis
Total oceanic biomass had decreased significantly. Total catch has declined. Catch per unit
effort has decreased.
What is causing this crisis?
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Expanding capture:
o Greater number of boats
o Expansion of new technologies
o Increased capture efficiency
o Food for aquaculture
Global climate change
o Phytoplankton declines
o Declining oxygen in global oceans
Calculation of maximum sustainable yield
o Policy disguised as science
Age specific mortality
o We target large, reproductive adults
o Bigger, older fish contribute disproportionately to reproduction
Ecosystem level factors
Spawning habitat degradation
Parasites and pathogens
Managements issues
Two Management Philosophies
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Regulation
o Control of fishing gear
o Duration
o Total quota
o License fees
No take zones/Marine Protected Areas
o Increased abundance of fish
 Biomass, density, species richness
o Can take up to 20 years to see changes
o Increased average size and age of fish
o Enhances fishery yields and nearby
Aquaculture
Aquaculture is the raising of aquatic plants and animals for human use or consumption. Fish
and other aquatic organisms provide up to 20 percent of the animal protein consumed
worldwide. Aquaculture may be one solution to the overharvesting of fish and other organisms
in the world’s oceans.
Aquaculture is not a new idea. This process probably began in China about 4,000 years ago.
Today, China leads the world in using aquaculture to produce freshwater fish. There are a
number of different methods of aquaculture. Among these are:

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Fish farming
Fish ranching
Fish farms generally consist of many individual ponds that each contain fish at a specific stage
of development. Fish grow to maturity in the ponds and are then harvested. Fish ranches raise
fish to a certain age, release them to the ocean, and then harvest the adults when they return
to their birthplace to breed.
As with other methods of food production, however, aquaculture can cause environmental
damage if not managed properly. Aquatic organisms can produce a large amount of waste,
which can be a source of pollution. Because aquaculture requires so much water, the process
can deplete local water supplies.
Disadvantages of Fish Farms
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Disease and parasites
o Ex. Sea lice in farmed salmon
Require large amounts of food
o 37% of all global seafood is now ground into feed
Waste products
Despite these problems, aquaculture will continue to be an important source of protein for the
human diet.
Livestock
Livestock is the term given to domesticated animals that are raised to be used on a farm or
ranch or to be sold for profit. Populations of livestock have changed dramatically in the last 50
years. Large livestock operations produce most of the meat that is consumed in developed
countries.
Species
Chickens
Sheep
Cattle
Pigs
Goats
Horses, donkeys,
and mules
GLOBAL ESTIMATE OF ANIMAL POPULATIONS
Global Livestock Populations
1961
2009
3.9 billion
18.6 billion
1 billion
1.1 billion
942 million
1.4 billion
406 million
942 million
349 million
880 million
110 million
113 million
Increase
377%
10%
49%
132%
152%
2.7%
In developing countries, livestock not only provide leather, wool, eggs, and meat, but also
serve other functions. Some livestock are used as draft animals to pull carts and plows. Other
livestock provide manure as the main source of plant fertilizer or as a fuel for cooking.
Ruminants
Ruminants are cud-chewing mammals that have a three- or four-chambered stomach. Cattle,
sheep, and goats are examples of ruminants. Cud is the food that these animals regurgitate
from the first chamber of their stomachs and chew again to aid digestion. When we eat the
meat of ruminants, we are using them to convert plant material, such as grass stems and
woody shrubs, into food that we can digest—such as beef.
Humans have created hundreds of breeds of cattle that are suited to life in different climates.
Worldwide meat production per person has increased significantly since 1950.
Poultry
Since 1961, the population of chickens worldwide has increased to a greater percentage than
the population of any other livestock. Chickens are a type of poultry, domesticated birds raised
for meat and eggs. In more-developed countries, chickens and turkeys are usually raised in
factory farms.
Environmental Impacts
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Requires a lot of land, water, and food
o 2/3 of agricultural land
Leads to increased grain prices
Cause 18% of global greenhouse gas emissions
o 35-40% of methane
o 64% of ammonia
Water pollution
o Waste, hormones, antibiotics
o The livestock industry in the US produces 116,000 pounds of waste per second