Transcript Notes - Aurora City School District

Section 1: Feeding the World
CH 15: FOOD AND AGRICULTURE
Objectives – Section 1
 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.
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.
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.
Humans and Nutrition
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.
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.
Sources of Nutrition
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.
Diets Around 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.
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.
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.
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.
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.
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.
World Food Problems
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.
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.
Droughts 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.
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.
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.
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,
and chemicals needed to grow new crop
varieties.
Section 2: Crops and Soil
CH 15: FOOD AND AGRICULTURE
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.
Crops and Soil
 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
 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.
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.

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.
Fertile Soil: The Living
Earth

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.

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.

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.
Soil Erosion: A Global
Problem
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.
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.
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.
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.
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.
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.
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.
Enriching the Soil
 Over the
past 50
years, the
use of such
inorganic
fertilizers has
increased
rapidly.
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.
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 United
States 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
•
•
•
•
pathogens,
plant defenses,
chemicals from plants,
and the 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.
Integrated Pest Management
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.
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.
Engineering a Better Crop
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.
Sustainable Agriculture
 Farming that conserves natural resources and
helps keep the land productive indefinitely is
called sustainable agriculture.
 Sustainable agriculture involves planting
productive, pest-resistant crop varieties that
require little energy, pesticides, fertilizer, and
water.
Section 3: Animals and Agriculture
CH 15: FOOD 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.
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.
Food from Water
The North Atlantic cod fishery has collapsed
because too many fish were harvested over time.
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.
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
 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.
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.
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.
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.
Livestock
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.
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.
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.
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.