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Chapter 15
Section 1 Feeding the World
Objectives
 Identify the major causes of malnutrition.
 Compare the environmental costs of producing different
types of food.
 Explain how food distribution problems and drought can
lead to famine.
 Explain the importance of the green revolution.
Chapter 15
Section 1 Feeding the World
Feeding the World
 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.
Chapter 15
Section 1 Feeding the World
Humans and Nutrition
 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 are carbohydrates,
proteins, and lipids. Our bodies need smaller amounts of
vitamins and minerals to remain healthy.
Chapter 15
Section 1 Feeding the World
Humans and Nutrition
Chapter 15
Section 1 Feeding the World
Humans and Nutrition
 Malnutrition is a disorder of nutrition that results when a
person does not consume enough of each of the 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 world, 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.
Chapter 15
Section 1 Feeding the World
Sources of Nutrition
 Diet is the type and amount of food that a person eats. A
healthy diet is one that maintains a balance of the right
amounts of nutrients, minerals, and vitamins.
 The foods produced in the greatest amounts worldwide are
grains, plants of the grass family whose seeds are rich in
carbohydrates.
 Besides eating grains, most people eat fruits, vegetables,
and smaller amounts of meats, nuts, and other foods that
are rich in fats and proteins.
Chapter 15
Section 1 Feeding the World
Sources of Nutrition
Chapter 15
Section 1 Feeding the World
Diets Around the World
 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 than people in
less developed countries.
Chapter 15
Section 1 Feeding the World
Diets Around the World
Chapter 15
Section 1 Feeding the World
The Ecology of Food
 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.
Chapter 15
Section 1 Feeding the World
Food Efficiency
 The efficiency of a given type of agriculture is a measure
of the 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.
Chapter 15
Section 1 Feeding the World
Food Efficiency
 On average, more energy, water, and land are used to
produced a Calorie of food from animals than to produce a
Calorie of food from plants.
 Animals that are raised for human use are usually fed plant
matter, but because less energy is available at each level
on a food chain, only about 10 percent of the energy from
the plants gets stored in the animals.
Chapter 15
Section 1 Feeding the World
Food Efficiency
 Thus, a given area of land can usually produce more food
for humans when it is used to grow plants than when it is
used to raise animals.
 The efficiency of raising plants for food is one reason why
diets around the world are largely based on plants.
 However, meat from animals generally provides more
nutrients per gram than most food from plants.
Chapter 15
Section 1 Feeding the World
Old and New Foods
 Researchers hope to improve the efficiency of food
production by studying plants and other organisms that
have high yield.
 Yield is the amount of crops produced per unit area.
 Researchers are interested in organisms that can thrive in
various climates and that do not require large amounts of
fertilizer, pesticides, or fresh water. Some organisms have
been a source of food for centuries, while other sources
are just being discovered.
Chapter 15
Section 1 Feeding the World
World Food Problems
 Some people become malnourished because they simply
do not get enough food.
 More food is needed each year to feed the world’s growing
population.
 World food production has been increasing for decades,
but now food production is not increasing as fast as the
human population is increasing.
Chapter 15
Section 1 Feeding the World
World Food Problems
Chapter 15
Section 1 Feeding the World
Unequal Distribution
 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.
 Wars and political strife can also lead to malnutrition
because they interrupt transportation systems.
Chapter 15
Section 1 Feeding the World
Droughts and Famines
 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.
Chapter 15
Section 1 Feeding the World
Drought and Famines
 People in a given area can usually survive one crop failure.
They may have saved enough food from previous seasons,
or they may have systems for importing food from
elsewhere.
 But several years of drought cause severe problems for
any area of the world.
 For example, after a long drought, the soil may be less
able to support the production of food crops.
Chapter 15
Section 1 Feeding the World
The Green Revolution
 Worldwide, between 1950 and 1970, increases in crop
yields resulted from the use of new crop varieties and the
application of modern agriculture techniques.
 These changes were called the green revolution. Since the
1950s, the green revolution has changed the lives of
millions of people.
 However, the green revolution also had some negative
effects.
Chapter 15
Section 1 Feeding the World
The Green Revolution
 For example, most new varieties of grain produce large
yields only if they receive large amounts of water, fertilizer,
and pesticides. In addition, the machinery, irrigation, and
chemicals required by new crop varieties can degrade the
soil if they are not used properly.
 As a result of the overuse of fertilizers and pesticides,
yields from green revolution crops are falling. The grain
production in the U.S. has decreased since 1990, partly
because the amount of water used for irrigation has
decreased.
Chapter 15
Section 1 Feeding the World
The Green Revolution
 In addition, the green revolution had a negative impact on
subsistence farmers, or farmers who grow only enough
food for local use.
 Before the green revolution, subsistence farmers worked
most of the world’s farms.
 But they could not afford the equipment, water, ad
chemicals needed to grow new crop varieties.
Chapter 15
Section 2 Crops and Soil
Objectives
 Distinguish between traditional and modern agricultural
techniques.
 Describe fertile soil.
 Describe the need for soil conservation.
 Explain the benefits and environmental impacts of pesticide
use.
 Explain what is involved in integrated pest management.
 Explain how genetic engineering is used in agriculture.
Chapter 15
Section 2 Crops and Soil
Crops and Soil
 Arable land is farmland that can be used to grow crops.
 The Earth has only a limited area of arable land.
 But, as the human population continues to grow, the
amount of arable land per person decreases.
Chapter 15
Section 2 Crops and Soil
Agriculture: Traditional
 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.
 These traditional techniques have been used since the
earliest days of farming.
Chapter 15
Section 2 Crops and Soil
Agriculture: Modern
 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.
Chapter 15
Section 2 Crops and Soil
Fertile Soil: The Living Earth
 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.
Chapter 15
Section 2 Crops and Soil
Fertile Soil: The Living Earth
Chapter 15
Section 2 Crops and Soil
Fertile Soil: The Living Earth
 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.
Chapter 15
Section 2 Crops and Soil
Fertile Soil: The Living Earth
 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.
Chapter 15
Section 2 Crops and Soil
Fertile Soil: The Living Earth
Chapter 15
Section 2 Crops and Soil
Soil Erosion: A Global Problem
 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.
 In the U.S., about half of the original topsoil has been lost
to erosion in the past 200 years.
 Without topsoil, crops cannot be grown. Yet, almost all
farming methods increase the rate of soil erosion.
Chapter 15
Section 2 Crops and Soil
Soil Erosion: A Global Problem
Chapter 15
Section 2 Crops and Soil
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
desertlike.
 This process is causing some of our arable land to
disappear.
Chapter 15
Section 2 Crops and Soil
Land Degradation
 For example, in the past, people who lived in the drier part
of the Sahel region in Africa grazed animals, while people
in the wetter part of the region planted crops.The grazing
animals were moved from place to place to find fresh
grass. The cropland was planted for only a few years, and
then allowed to lie fallow, or to remain unplanted, for
several years.
 These methods allowed the land to adequately support the
people in the Sahel.
Chapter 15
Section 2 Crops and Soil
Land Degradation
 But the population in the region has grown, and the land is
being farmed, grazed, and deforested faster than it can
regenerate. Crops are planted too frequently and fallow
periods are being shortened or eliminated completely.
 As a result, the soil is losing fertility and productivity.
Because of overgrazing, the land has fewer plants to hold
the topsoil in place.
 So, large areas have become desert and can no longer
produce food.
Chapter 15
Section 2 Crops and Soil
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.
 For example, soil-retaining terraces can be build across a
hillside. On gentler slopes, contour plowing, which consists
of plowing across the slope of a hill instead of up and down
the slope, can be used.
Chapter 15
Section 2 Crops and Soil
Soil Conservation
 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.
Chapter 15
Section 2 Crops and Soil
Soil Conservation
 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.
Chapter 15
Section 2 Crops and Soil
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,
phosphorous, 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.
Chapter 15
Section 2 Crops and Soil
Enriching the Soil
 Over the past 50 years, the use
of such inorganic fertilizers has
increased rapidly.
Chapter 15
Section 2 Crops and Soil
Enriching the Soil
 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.
Chapter 15
Section 2 Crops and Soil
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.
Chapter 15
Section 2 Crops and Soil
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.
Chapter 15
Section 2 Crops and Soil
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.
Chapter 15
Section 2 Crops and Soil
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.
Chapter 15
Section 2 Crops and Soil
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.
Chapter 15
Section 2 Crops and Soil
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 United States
for decades but can still be detected in the environment.
Chapter 15
Section 2 Crops and Soil
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
• pathogens,
• plant defenses,
• chemicals from plants,
• and the disrupting of insect breeding
Chapter 15
Section 2 Crops and Soil
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.
Chapter 15
Section 2 Crops and Soil
Integrated Pest Management
Chapter 15
Section 2 Crops and Soil
Integrated Pest Management
 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.
Chapter 15
Section 2 Crops and Soil
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.
Chapter 15
Section 2 Crops and Soil
Engineering a Better Crop
Chapter 15
Section 2 Crops and Soil
Implications of Genetic
Engineering
 In the United States, we now eat and use genetically
engineered agricultural products everyday.
 Many of these products, however, have not been fully
tested for their environmental impacts.
 Some scientists warn that these products will cause
problems in the future.
Chapter 15
Section 2 Crops and Soil
Sustainable Agriculture
 Farming that conserves natural resources and helps keep
the land productive indefinitely is called sustainable
agriculture.
 Sustainable agriculture involves planting productive, pestresistant crop varieties that require little energy, pesticides,
fertilizer, and water.
Chapter 15
Section 3 Animals and
Agriculture
Objectives
 Explain how overharvesting affects the supply of aquatic
organisms used for food.
 Describe the current role of aquaculture in providing
seafood.
 Describe the importance of livestock in providing food and
other products.
Chapter 15
Section 3 Animals and
Agriculture
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.
Chapter 15
Section 3 Animals and
Agriculture
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.
Chapter 15
Section 3 Animals and
Agriculture
Food from Water
The North Atlantic cod fishery has collapsed
because too many fish were harvested over time.
Chapter 15
Section 3 Animals and
Agriculture
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.
Chapter 15
Section 3 Animals and
Agriculture
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.
Chapter 15
Section 3 Animals and
Agriculture
Aquaculture
 Aquaculture is not a new idea.
 This practice probably began in China about 4,000 years
ago.
 Today, China leads the world in using aquaculture to
produce freshwater fish.
Chapter 15
Section 3 Animals and
Agriculture
Aquaculture
 There are a number of different methods of
aquaculture. Among these are
• 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.
Chapter 15
Section 3 Animals and
Agriculture
Aquaculture
 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.
 Despite these problems, aquaculture will continue to
be an important source of protein for the human
diet.
Chapter 15
Section 3 Animals and
Agriculture
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 40 years.
 Large livestock operations produce most of the meat that is
consumed in developed countries.
Chapter 15
Section 3 Animals and
Agriculture
Livestock
Chapter 15
Section 3 Animals and
Agriculture
Livestock
 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.
Chapter 15
Section 3 Animals and
Agriculture
Ruminants
 Ruminants are cud-chewing mammals that have a threeor 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.
Chapter 15
Section 3 Animals and
Agriculture
Ruminants
 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.
Chapter 15
Section 3 Animals and
Agriculture
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.