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Food, Soil, and
Science Focus: Soil is the Base of Life on Land
A. Soil is a thin covering that is made of eroded rock, minerals, decaying organic matter, water, air, and billions
of living organisms. It covers most of the earth and provides nutrients for plant growth.
B. Soils are formed by a break down of rock, decomposing surface litter and organic matter. Bacteria and
other decomposer microorganisms break down some of soil’s organic compounds into simpler inorganic
compounds.
1. Soil is a renewable resource.
2. The formation of 1 cm of soil can take from 15 to 100 years, depending on the climate.
C. Soil provides nutrients for plant growth, is the earth’s primary filter for cleansing water and for
decomposing and recycling biodegradable wastes.
D. The soil can develop many layers.
1. Mature soils have developed over a long time, are arranged in soil horizons (series of horizontal
layers), have distinct textures and compositions in these layers that vary among different types of soils.
2. Cross-sectional views of these layers are soil profiles.
3. The layers/horizons of mature soils have at least four parts.
a. The top part/layer is the surface litter layer or O horizon. This layer is brown/black and
composed of leaves, twigs, crop wastes, animal waste, fungi and other organic material.
b. The topsoil layer or A horizon is composed of decomposed organic matter called humus, as well
as some inorganic mineral particles. Thick topsoil layers help hold water and nutrients. These
two top layers teem with bacteria, fungi, earthworms, and small insects.
1) Dark-brown/black topsoil is rich in nitrogen and organic matter.
2) Gray, yellow or red topsoils need nitrogen enrichment.
c. The B horizon (subsoil) has most of the soil’s inorganic matter—sand, silt, clay, and gravel.
d. The C-horizon (parent material) rests on bedrock.
e. Air and water fill spaces between soil particles. Plant roots need oxygen for aerobic respiration.
4. Downward movement of water through the spaces in the soil is infiltration. Water moving downward
dissolves minerals and organic matter and carries them to lower levels; this process is leaching.
E. There are thousands of different types of soils based upon a variety of soil properties.
1. Soil texture – differences in texture are affected by the size of particles and the space between
particles. A soil’s texture can be one of the following (or any combination):
a. Sand – this soil is easy to work.
b. Clay – these retain a lot of water.
c. Silt
d. Loam – they hold water.
2. Moisture content
3. Organic matter
4. Bulk density
5. Fertility (N, P, K, pH)
6. Porosity/Permeability – soil porosity is affected by soil texture. The average size of spaces or pores
in soil determines soil permeability (how well water moves through it).
Geologic Timescale –
A. Geologists created the geologic timescale to visually divide the history of the Earth into time intervals.
1. The Earth is 4.6 billion years old.
2. Humans have existed for only the very last tiny part of the timescale.
B. Time intervals in the geologic time scale are variable.
1. Some are based on new biological developments and others are based on major extinction events.
14-1 What are the earth’s major geological processes and hazards?
A. The earth is made up of a core (inner core and outer core), mantle, and crust and is constantly changing
as a result of processes taking place on and below its surface. Geology is the study of dynamic processes
occurring on the earth’s surface and in its interior.
1. The core is intensely hot. It has a solid inner core surrounded by a liquid outer core of molten or
semisolid material.
2. The mantle is a thick zone of very hot, partly melted rock about the consistency of soft plastic. The
upper part of the mantle is also called the asthenosphere.
3. The crust is solid rock that floats on the mantle of partly melted rock. The crust, or lithosphere, is
thin and is divided into the continental crust and the oceanic crust.
B. Plate Tectonics is a theory that states that the Earth’s crust is broken up into huge tectonic plates that
move around as the result of large convection currents in the earth’s interior.
1. About 12 or so rigid tectonic plates move across the surface of the mantle very slowly.
2. Evidence for the movement of these plates are the fit of the continents, similar rock, fossil, and
mountains on opposite sides of oceans, and evidence of past climates that don’t match the continent’s
current location.
3. There are three types of boundaries for lithospheric plates. The boundaries are divergent plate
boundaries, where plates move apart in opposite directions, convergent plate boundaries, where
plates are pushed together by internal forces and one plate rides up over the other. The third type is a
transform fault boundary and occurs where plates slide/grind past one another.
4. The movement of these plates produces mountains on land and trenches on the ocean floor.
5. Earthquakes (violent releases of energy as a result of plates rubbing up against one another) and
volcanoes (holes in the ground through which liquid magma is ejected) are violent and disruptive
actions of the earth. Volcanoes and earthquakes are likely to be found at the plate boundaries.
6. The plate tectonic theory also helps to explain certain patterns of biological evolution occurred.
C. Some processes wear down the earth’s surface by moving topsoil and pieces of rock from one place to
another. Weathering is the physical, chemical, and biological processes that break down rocks and
minerals into smaller pieces. This is an important step in the formation of soil.
1. Weathering can occur as a result of wind, water, or the freezing action of water.
14-2 How are the earth’s rocks recycled?
A. The earth’s crust consists of solid inorganic elements and compounds called minerals and rocks.
Because they take so long to produce, these components of the earth’s natural capital are classified as
nonrenewable resources.
1. A mineral is an element or inorganic compound that is solid with a regular internal crystalline structure.
2. A mineral resource (ore) is a concentration of naturally occurring material in or on the earth’s crust
that can be extracted and processed into useful materials at an affordable cost.
a. Examples of mineral resources are fossil fuels (coal, oil, and natural gas), metallic minerals (such
as aluminum, iron, and copper), and nonmetallic minerals (such as sand, gravel, and limestone).
b. Mineral resources can exist as high grade ore (a large percentage of desired mineral) and low
grade ore (a small percentage of desired mineral).
3. Mineral resources can be classified into four major categories:
a. Identified resources with a known location, quantity, and quality.
b. Reserves are identified resources that can be extracted profitably at current prices.
c. Undiscovered reserves are potential supplies of a mineral resource assumed to exist.
d. Other resources are undiscovered resources and identified resources not classified as reserves.
B. Deposits of nonrenewable mineral resources in the earth’s crust vary in their abundance and distribution.
1. Iron and aluminum are fairly abundant whereas manganese, chromium, cobalt, and platinum are scarce.
2. Massive exports can deplete a countries supply of nonrenewable minerals.
3. Three countries (the United States, Canada, and Russia) with only 8% of the world’s population
consume about 75% of the world’s most widely used metals.
4. Japan has virtually no metal resources and has to rely on resource imports.
6. Experts are concerned about the availability of four strategic metal resources (manganese, cobalt,
chromium, and platinum) that are essential for the country’s economic and military strength.
C. A very slow chemical cycle recycles three types of rock found in the earth’s crust. This recycling
process is known as the rock cycle.
1. Rock is a solid combination of one or more minerals.
3. Igneous rock is formed below or on the earth’s surface when molten rock wells up and hardens.
They form the bulk of the earth’s crust.
4. Sedimentary rock is formed from small, eroded pieces of rock that are carried to downhill sites.
Layers accumulate over time and an increase of weight and pressure plus dissolved minerals bind the
sediment particles together to form sedimentary rock.
5. Metamorphic rock is produced from preexisting rock that is subjected to high temperatures, high
pressures, chemically active fluids, or some combination of these.
6. The rock cycle is the interaction of physical and chemical processes that change rock from one type
to another. It is the slowest of the earth’s cyclic processes.
14-3 What are mineral resources and what are the environmental effects of using them?
A. The extraction, processing, and use of mineral sources have a large environmental impact. The greatest
environmental damage may be from the processes used to get the ore out of the ground.
1. Higher grade ores are more easily extracted.
2. Greater environmental damage comes with extraction of lower grade ores in higher energy costs and
greater environmental damage to the land.
B Minerals are removed through a variety of methods that vary widely in their costs, safety factors, and
levels of environmental harm. Shallow deposits are removed by surface mining, and deep deposits are
removed by subsurface mining.
1. In surface mining, the overburden of rock and soil is removed and discarded as spoils.
2. Surface mining is done by one of several methods:
a. Open-pit mines are large holes dug to remove ores
b. Strip mining is useful and economical for extracting mineral deposits that lie close to the earth’s
surface; area strip mining is used where land is relatively flat
c. Contour strip mining is used on mountainous land where a series o f terraces are cut into the hill
d. Mountain-top removal involves the use of explosives and huge machines to remove the top of a
mountain to expose seams of coal.
3. Subsurface mining removes coal and various metal ores too deep for surface mining.
4. Subsurface mining disturbs less than 1/10 as much land as surface mining with less waste, but is
more dangerous and expensive.
C. Mining scars the land and produces large amounts of solid waste and air and water pollution.
1. Subsidence from underground mining causes sewer, gas and water systems to break.
2. Mining wastes contain toxins and acid drainage carries to streams and groundwater.
3. Toxic chemicals can also be emitted to the atmosphere.
D. After waste material is removed from metal ores they are smelted or treated with chemicals to extract
the desired metal.
1. Ore has two components: the ore mineral and the waste material called gangue.
2. Removing the gangue from ores produces large piles of solid waste called tailings.
3. Ore is separated from gangue, smelted to obtain the metal, made into products that are used and
discarded or recycled.
4. There can be enormous amounts of air and water pollution from these processes.
14-4 How long will supplies of nonrenewable mineral resources last?
A. The future supply of a resource depends on its affordable supply and how rapidly that supply is used. A
nonrenewable resource generally becomes economically depleted rather than totally depleted.
B. When a nonrenewable mineral resource becomes depleted, there are five choices: recycle or reuse
existing, supplies, waste less, use less, find a substitute, or do without
C. Depletion time for a resource depends on how long it takes to use up a certain proportion (usually 80%)
at a given rate of use.
1. Depletion time is extended by recycling, reusing and reducing consumption of a given resource.
2. New discoveries of a resource extend the depletion time also.
3. The demand for mineral resources is increasing at a rapid rate with increased consumption.
4. No one knows whether we will run out of a mineral resource.
D. New technologies can increase the mining of low-grade ores at affordable prices, but harmful
environmental effects can limit this approach.
1. One limiting factor in mining low-grade ore is the increased cost of mining; another is the availability
of freshwater that is needed to mine and process some minerals; a third is the environmental impacts
of increased land disruption, waste material, and pollution produced during mining and processing.
E. Most minerals in seawater and on the deep ocean floor cost too much to extract, and there are squabbles
over who owns them. Rich hydrothermal deposits of gold, silver, zinc, and copper are found as sulfide
deposits in the deep-ocean floor and around hydrothermal vents. Another potential source from the
ocean floor is potato-sized manganese nodules that cover about 25–50% of the Pacific Ocean floor.
F. Mining legislation
1. The U.S. General Mining Law of 1872
a. Encouraged mineral exploration and mining of hard-rock minerals (gold, silver, copper, nickel)
on U.S. public lands and led to the developed/settlement of the American West (1800s)
b. Until 1995, land could be bought for 1872 prices and so now an estimated $285 billion of mineral
resources now owned/ controlled by private companies, 1/5 are foreign.
2. The Surface Mining Control and Reclamation Act of 1977 (in the U.S.) requires mining companies
to restore most surface-coal mines. There are no laws to control or reclaim lands from other types of
mines, like hard-rock, etc.
a. Reclamation is an attempt to return mined land back to its original state (or at least a functional
ecosystem…reforestation, used for recreation, commercial use
b. Reclamation efforts are only partially successful.
14-5 How can we use mineral resources more sustainably?
A. Scientists and engineers are developing new types of materials that can serve as substitutes for many
metals. This is known as the materials revolution.
1. Development of silicon and ceramics may replace the need for as much metal. Ceramics have many
advantages over conventional metals (harder, stronger, lighter, last longer) and do not corrode.
2. Automobiles and planes are being made of plastics and composite materials since they cost less to
make, are lower maintenance and can be molded to any shape. Use of plastics has drawbacks; they
require the use of oil and other fossil fuels.
3. Nanotechnology is the use of science and engineering at the atomic and molecular level to build
materials with specific properties. One concern about nanotechnology is that smaller particles tend
to be more reactive and potentially more toxic due to large surface area compared to mass.
B. Recycling valuable and scarce metals saves money and has a lower environmental impact than mining
and extracting them from their ores. In many cases, metals are actively recycled.
C. We can use mineral resources more sustainably by reducing their use and waste and by finding
substitutes with fewer harmful environmental effects.
Where do species come from?
A. Evolution is the change in a population’s genetic makeup over time.
B. Populations evolve by becoming genetically different.
C. Theory of evolution – all species descended from earlier, ancestral species.
1. Over time, a population’s gene pool changes when mutations (beneficial changes) in DNA molecules
are passed on to offspring. There may be several different forms (alleles) of a single gene.
2. Sexual reproduction leads to random recombination of alleles from individual to individual.
3. The population develops genetic variability brought about by mutations.
a. Mutations are random changes in the structure/number of DNA molecules in a cell.
b. The only mutations that matter to evolution are the ones passed to offspring.
D. Natural selection’s role in biological evolution occurs when members of a population have genetic traits
that improve their ability to survive and produce offspring with those specific traits.
1. For natural selection to evolve in a population, three conditions are necessary:
a. The population must have genetic variability.
b. The trait must be heritable, capable of being passed from one generation to another.
c. The trait must enable individuals with the trait to produce more offspring than individuals without
the trait; this is differential reproduction.
2. Adaptations or adaptive traits are heritable traits that help organisms to survive and reproduce better
under prevailing environmental conditions.
3. Environmental changes require adaptations also. Organisms must:
a. Adapt to the new conditions.
b. Migrate to an area with more favorable environment.
c. Become extinct.
CASE STUDY: Humans have thrived so well as a species because of their strong opposable thumbs,
ability to walk upright, and complex brain. These adaptations may not prove as beneficial as the
environment continues to change, though our powerful brain may allow us to live more sustainably in
the future.
E. Natural selection can only act on existing genes and is limited by reproductive capacity.
1. The only genetic traits that can adapt are those already in the gene pool.
2. A population’s reproductive capacity limits those genes that can adapt.
a. Genetically diverse species that reproduce quickly, can often adapt quickly.
b. Populations that reproduce slowly take a long time to adapt through natural selection.
4-3 How do geologic processes and climate change affect evolution?
A. Processes such as the shifting of tectonic plates, volcanic eruptions, and earthquakes influence earth’s
climate and in turn affect evolution by removing and/or isolating habitats and species.
B. Long-term climate changes relocate ecosystems, thus determining where certain species can live.
C. Asteroids and meteorites have caused environmental stress and mass extinctions.
4-4 How do speciation, extinction, and human activities affect biodiversity?
A. Natural selection can lead to development of an entirely new species. In speciation, two species arise
from one when some members of a population cannot breed with other members to produce fertile
offspring.
1. Speciation occurs as a result of reproductive isolation. The gene pools are so changed that members
become so different in genetic makeup that they cannot produce fertile offspring.
a. Geographic isolation - physical separation for long time periods
b. Temporal isolation – differences in the timing of activities
c. Behavioral isolation – specific behavior differences prevent mating
B. When population members cannot adapt to changing environmental conditions, the species becomes
extinct.
1. A species manages to survive one to ten million years before extinction occurs.
2. Life has had to cope with many major natural disasters that may reduce or eliminate species.
3. Introduction of new species into an area has also led to reduction in number or elimination of species.
3. Endemic species are those found nowhere else on earth and are often found in island habitats.
Habitat islands are a habitat surrounded by a different one, such as a national park surrounded by
logging, mining, etc. activities.
a. Habitat fragmentation leads to species vulnerability to predators, disease, etc.
b. Species are limited in their ability to colonize new areas, find mates and food.
C. When local environmental conditions change, some species will disappear at a low rate; this is called
background extinction.
D. Mass extinction is a significant rise in extinction rates above the background extinction level. Usually,
from 25-70% of species are lost. Recent evidence suggests that there have been three mass extinctions
on earth.
SCIENCE FOCUS:
A. Man has used artificial selection to change the genetic characteristics of populations.
1. We use selective breeding to obtain specific desired traits.
2. Traditional crossbreeding is a slow process; it takes many generations of selection for the desired
trait.
3. Genetic engineering is a technique that isolates, modifies, multiplies, and recombines genes from
different organisms. Genes from different species that would never interbreed in nature are being
transferred to each other.
What is food security and why is it difficult to attain?
A. Global food production has stayed ahead of population growth, but one in six people in developing
countries cannot grow or buy the food they need.
B. Some people cannot grow or buy enough food to meet their basic energy needs and to get enough protein
and other key ingredients. People need fairly large amounts of macronutrients (protein, carbohydrates,
fats) and smaller amounts of micronutrients (vitamins such as A, C, E) and minerals (iron, iodine,
calcium).
1. Undernutrition is suffered by those who can’t grow or buy enough food.
2. Malnutrition results from insufficient protein and other key nutrients.
C. One in three people has a deficiency of one or more vitamins and minerals.
1. Blindness due to a vitamin A deficiency occurs in 250,000 children under 6 each year and up to 80%
die within a year.
2. Iron is needed to prevent anemia.
3. Iodine is needed for proper thyroid function, to prevent brain damage or formation of a goiter.
D. Droughts, floods, wars, and other catastrophic events can lead to severe food shortages that cause mass
starvation, many deaths, and economic and social disruption.
E. Overnutrition and lack of exercise can lead to obesity, reduced life quality, poor health, and premature
death.
12-2 How is food produced?
A. Food production from croplands, rangelands, ocean fisheries, and aquaculture has increased
dramatically.
1. Grain from croplands produce 77% of the world’s food.
2. Meat from rangelands and feedlots produce about 16% of the world’s food.
3. Fish from oceanic fisheries and aquaculture supply 7% of the world’s food.
4. All three systems have increased their food yields since 1960.
a. Technological advances have increased food production or harvesting.
b. More sophisticated farming techniques have been developed.
c. Expanded use of chemical fertilizers, irrigation, pesticides, high-yield crops have developed.
d. Intense farming methods, such as densely populated feedlots and enclosed breeding/growing
pens, and aquaculture ponds or ocean cages have been implemented.
B. Wheat, rice and corn provide more than half of the calories in the food consumed by the world’s people.
C. About 80% of the world’s food supply is produced by industrialized agriculture.
1. Industrialized/high-input agriculture produces large quantities of single crop or livestock animals.
a. This uses much energy, water, fertilizers and pesticides to produce monocultures.
b. Plantation agriculture is industrialized agriculture, primarily in tropical developing countries to
produce cash crops—bananas, coffee, soybeans, and sugarcane.
CASE STUDY: The United States uses industrialized agriculture and green revolution techniques to
produce about 17% of the world’s grain.
D. Many farmers in developing countries use traditional/low-input agriculture to grow a variety of crops
on each plot of land (polyculture).
1. Traditional agriculture provides about 20% of the food supply and is practiced by 42% of the world.
a. Traditional subsistence agriculture typically supports a single farm family’s survival.
b. Traditional intensive agriculture strives to feed not only the farmer’s family, but also additional
food to sell as income. By using fertilizer, irrigating, etc., a higher yield is sought.
E. Since 1950, high-input agriculture has produced more crops per unit of land. The following steps
describe this green revolution:
1. Key grain crops are bred or enhanced to produce high-yield varieties.
2. High-yields are sustained by using large amounts of fertilizer, water, and pesticides.
3. The use of machinery and fossil fuel to plant and harvest.
4. A second green revolution has taken place as a result of fast-growing rice and wheat varieties bred
for tropical climates like China and India.
F. Modern agriculture has a greater harmful environmental impact than any human activity.
G. The gene revolution refers to increased crop yields as a result of mixing the genes of different
organisms. Farmers and scientists have used crossbreeding and artificial selection to develop genetically
improved varieties of crop strains.
1. Genetic engineering, which splices a gene from one species into the DNA of another species, is
creating improved strains of crops and livestock animals.
a. More than 2/3rds of food products on the U.S. shelves contain ingredients made from genetically
engineered crops.
b. Genetic engineering holds much promise but has some disadvantages. GMF (genetically modified
food) may possibly solve the world’s food problems but has also generated much controversy and
fear.
c. There is controversy over legal ownership of genetically modified crop varieties and whether
genetically modified foods should be labeled.
H. About half the world’s meat is produced by livestock grazing on grass and half is produced in feedlots
under factory-like conditions.
1. Industrialized animal production accounts for about 43% of the world’s beef production, half of pork
production, 68% of the egg production, and almost three-fourths of the world’s poultry production.
2. Meat produces large amounts of animal waste and pollutes the environment.
3. Raising cattle on rangelands and pastures is less environmentally destructive than raising them in
feedlots.
I. Aquaculture is the process of raising fish and shellfish for food like crops, rather than harvesting them
in the seas and inland waters. Fish farming cultivates fish in a controlled environment and harvests
them at a particular size. It is the world’s fastest growing type of food production.
12-3 What environmental problems arise from food production?
A. Soil erosion lowers soil fertility and can overload nearby bodies of water with eroded sediment.
1. Water, wind and people cause soil erosion; soil components are moved from one place to another.
2. Eroded soil becomes sediment in surface waters where it pollutes water, kills fish, clogs irrigation
ditches, channels, reservoirs and lakes.
3. Soil is eroding faster than it is forming on more than one-third of the world’s cropland.
B. About one-third of the world’s land has lower productivity because of drought and human activities that
reduce or degrade topsoil.
1. Desertification occurs when production falls by 10% or more though a combination of natural
causes (drought) and human activities. It may be moderate, severe or very severe, only in extreme
cases does it lead to a desert.
2. Repeated irrigation can reduce crop yields by causing salinization (salt buildup in the soil) and
waterlogging of croplands.
a. Salts left behind when irrigation water is not absorbed into the soil can be left in the topsoil.
b. Waterlogging occurs when saline water (from irrigation) envelops the deep roots of plants. This
saline water accumulates underground and raises the water table.
C. Industrialized food production requires large amounts of energy…about 17% of all commercial energy
use in the U.S.
How can we improve food security?
A. Use government policies to improve food production and security.
B. Simple and relatively inexpensive actions can have large impacts. One-half to two-thirds of nutritionrelated childhood death could be prevented for $5–10 per child per year.
1. Provide immunization.
2. Encourage breast-feeding.
3. Prevent dehydration.
4. Prevent blindness with a vitamin A capsule twice a year, at a cost of 75 cents per child.
5. Provide family planning services.
6. Increase education for women.
12-6 How can we produce food more sustainably?
A. Sustainable agriculture through soil conservation—Soil conservation seeks ways to reduce soil erosion
and restore soil fertility, mostly by keeping the soil covered with vegetation.
B. Specific planting techniques can also decrease soil erosion:
1. Terracing converts the land into a series of broad, nearly level terraces that run across the contour of
the land. This method holds water for crops and reduces runoff.
2. Contour farming plows and plants crops in rows across the slope of the land, not up and down.
Each row acts as a small dam.
3. Strip cropping plants alternating strips of a row crop (corn/cotton) with another crop that completely
covers the soil (grass/legume). Runoff is caught by the cover crop.
4. Leave crop residues on the land after harvest. (no-till farming)
5. Windbreaks of trees reduce wind erosion, help retain soil moisture, provide fuelwood, and support
bird and insect habitats.
C. Modern farm machinery can plant crops without disturbing the soil.
1. Conventional-tillage farming means plowing in the fall and leaving the soil bare all winter, making it
vulnerable to wind and erosion.
3. Minimum-tillage farming allows the soil to rest over the winter. The subsurface soil is broken up
and loosened but the topsoil is not turned.
4. No-till farming uses special machines to inject seeds, fertilizers, and herbicides into thin slits in the
unplowed soil and, then, cover the slits.
D. Fertilizers can help restore soil nutrients, but runoff of inorganic fertilizers can cause water pollution.
1. Organic fertilizer can be used to restore lost plant nutrients.
a. Animal manure improves soil structure, adds nitrogen, and stimulates soil bacteria and fungi.
c. Green manure plows freshly cut or growing green vegetation into the soil to increase organic
matter and humus.
d. Microorganisms in the soil break down organic matter in leaves, food wastes, paper and wood to
form compost.
2. Crop rotation plants different crops to replenish the soil, especially if a previous crop has depleted
the soil of certain nutrients.
3. Commercial inorganic fertilizers, used with organic fertilizers, can restore soil fertility.
a. Commercial inorganic fertilizers contain nitrogen (N), phosphorus (P), and potassium (K).
E. In organic farming the food is produced without the use of pesticides, synthetic fertilizers, antibiotics,
growth hormones, or genetic modification. According to the USDA, food products must meet all of
these provisions if they are labeled as organic.