Download File - C. Shirley Science EJCHS

Environmental Science
Environmental Science is the study of human IMPACT on the environment. The goal is to understand
and solve environmental problems. Two types of interactions are studied: how we use natural
resources & how our actions alter our environment.
Environmental science is an interdisciplinary science which
means that it involves many fields of study. Including ecology
which is the study of how living things interact with each other and
with their nonliving environment. Other sciences such as
chemistry, botany, geology and paleontology are used to help
gather information on the environment.
How is this basic concept
related to the fact that it is often
difficult for people to reach an
agreement about environmental
issues?
Our Environment Through Time
Hunter & Gatherers – People who obtain food by collecting plants and by hunting wild animals or
scavenging their remains. Early groups were small, and they migrated from place to place as different
types of food became available at different times of the year.
o Impact on environment: Native American tribes hunted bison on the grassland. Tribes set
fires to burn prairies and prevent growth of trees which maintained the open grassland. In
North America, a combination of rapid changes and overhunting by tribes may have led to
the disappearance of some species of large mammals (i.e. giant sloths, saber-toothed cats,
etc.).
Agricultural Revolution – Many hunter-gatherer groups began to collect seeds of plants and
domesticate animals in their environment. Agriculture began…..the practice of growing, breeding and
caring for plants and animals that are used for food, clothing, housing, transportation, and other
purposes. Agriculture practices began over 10,000 years ago and allowed human populations to grow
at an unprecedented rate.
o Impact on environment: Populations began to concentrate in smaller areas which placed
increase pressure on local environments. It changed the food we eat. Domesticated plants
became very different from their wild ancestors. Habitats were destroyed as areas are
replaced by farmland. Replacing forest with farmland on a large scale can cause soil loss,
floods and water shortages. Much of the converted land was farmed poorly and was no
longer fertile.
Industrial Revolution – For almost 10,000 years, tools were powered mainly by humans or animals.
In 1700s, energy sources shifted from animal muscle and running water to fossil fuels (coal, oil).
o Impact on environment: Increased use of fossil fuels greatly increased the efficiency of
agriculture, industry and transportation. Large-scale production of goods in factories
became less expensive than the local production of goods. Machinery reduced the amount
of land and labor needed for farming. Fewer people grew their own food and urban
populations grew larger. Fossil fuels and motorized vehicles allowed food and other goods
to be transported cheaply across great distances.
o Improving quality of life: Inventions (light bulb, etc) and technologies (telephone, etc)
enabled people to work and communicate more easily. Agriculture productivity increased
and sanitation, nutrition and medical care vastly improve.
Earth is a closed system - The only thing that enters Earth’s atmosphere in large amounts is
energy from the sun and the only thing that leaves in large amounts is heat. Resources are limited so
as the population grows, the resources will be used. As a result, more waste will be produces more
quickly than can be disposed. Environmental problems may occur on different scales: local, regional
or global.
Population growth: a local pressure…..agriculture
and industrial revolution has allowed the human
population to grow much faster than it had ever
grown before. The development of modern
medicine and sanitation helped the populations
increase. Producing enough food for such a large
population has environmental consequences.
What are our MAIN environmental problems?
1. Resource depletion – Renewable resources can
be replaced relatively quickly by natural
processes (i.e. fresh water, air, soil, trees and
crops). Nonrenewable resources form at a much
slower rate than the rate it is consumed (i.e.
minerals and fossil fuels). It may take millions of
years to replenish it.
2. Pollution – Waste is produced faster than it can
be disposed of and accumulates in the environment which causes pollution. Pollution is an
undesired change in air, water or soil that adversely affects the health, survival or activities of
humans or other organisms. There are two main types of pollutants: Biodegradable pollutants the
can be broken down by natural processes (i.e. human sewage, food waste, etc). Nondegradable
pollutants cannot be broken down by natural processes (i.e. mercury, lead, etc).
3. Loss of Biodiversity – Biodiversity refers to the number & variety of
Why should we be
species that live in an area. Around 99% of all species have become
concerned about the
extinct from Earth.
Economics and the Environment – Economic forces influence
modern extinction of an
individual species?
how we use resources.
1. Supply and Demand – The greater the demand for a limited supply of something, the more that
thing is worth. (i.e. production of oil & price)
2. Costs and Benefits – A cost-benefit analysis balances the cost of the action against the benefits
one expects from it. Analysis often depends on who is doing the analysis (i.e. industry, etc).
3. Risk Assessment – Cost-benefit analysis involves risk assessment, which helps us create costeffective ways to protect our health and the environment. To develop an effective solution to an
environmental problem, the public must perceive the risk accurately.
Developed and Developing Countries – The unequal distribution of wealth and resources around
the world influences the environmental problems that a society faces and the choices it can make.
Developed countries have higher average incomes, slower population growth, diverse industrial
economics, and stronger social support systems (i.e. U.S., Canada, Japan, Western Europe).
Developing countries have lower average incomes, simple and agriculture-based economics, and
rapid population growth.
Population and Consumption – Most environmental problems can be traced to 2 root causes. (1)
The human population in some areas is growing too quickly for the local environment to support it. (2)
People are using up, wasting, or polluting many natural resources faster than they can be replaced or
cleaned up.
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Local Population Pressures – When population grows, there may not be enough natural resources
for everyone in the area resulting in topsoil being stripped of essential minerals and animals are
driven to extinction. Malnutrition, starvation and disease can be constant threats. Food production,
education and job creation can’t keep pace with the population growth, so fewer than half have
access to enough food, safe drinking water and proper sanitation.
Consumption Trend – Developing countries use 75% of the world’s resources, even though they
make up only about 20% of the world’s population.
Ecological Footprints – This footprint shows the
productive areas of Earth needed to support one person
in a particular country. It estimates the land used for
crops, grazing, forest products and housing. It also
estimates the ocean area used to harvest seafood and
the forest area needed to absorb the air pollution
caused by fossil fuels.
FYI: Learn to think critically to help you make
informed decisions. Investigate the source of
information you encounter.
Sustainable World – Most people support a key goal of environmental science: achieving
sustainability. Sustainability is the condition in which human needs are met in such a way that a
human population can survive indefinitely. This includes technology advances and human civilizations
continue to be productive.
TOOLS of Environmental Science
Scientific Method – series of steps used to answer questions.
1. Observation – gathering information by using our senses.
2. Hypothesis – a testable explanation that leads to a scientific
explanation. A logical prediction about what will happen.
3. Experiment – procedure designed to test a hypothesis under
controlled conditions. A single variable is tested and is the
only difference between the two groups: experimental group &
control group.
 Experimental group – the group that contains the
changed variable being tested.
 Control group – the group that remains constant. This
group is used as a standard for comparison.
 Constants are variables that remain the same in both
groups.
 Independent variable – the variable being tested or is
changed.
 Dependent variable – the result from the changed
variable.
4. Data – Gather and analyze information (data) which can be organized into tables and graphic
illustrations to help analyze the data.
5. Conclusion – Compare the outcome of the experiment with the hypothesis. Experiments can be
repeated to ensure conclusions are reliable. Then scientist can publish their findings. Through
repeated testing and inquiry of the hypothesis from other scientist, well-tested hypothesis can
become a theory.
Correlation Method – When using experiments to answer questions is impossible or unethical,
scientists test predictions by examining correlations, or associations between two or more events.
Although correlations are useful, they do not necessarily prove cause-and-effect between two
variables.
Statistics & Models – Environmental science provides a lot of data that needs to be organized and
interpreted before it’s useful.
 Statistics – the collection and classification of data that are in the form of numbers. Mean or
average provides a single measure for a given characteristics of a population. Distribution
is the relative arrangement of members of a statistical population. Probability can be used
to give the chance that something will happen. Sample is a group of individuals or events
selected to represent the population (i.e. population size). Scientist try to make sure the
samples taken are large enough to give an accurate estimation of the whole population.
Risk is used to determine the probability of an unwanted outcome.
 Models – representations of objects or systems (i.e. physical, graphical, conceptual, or
mathematical models).
Making Informed Decisions – Examine values which are principles or standards we consider
important. Decision-making model is a conceptual model that provides a systemic process for making
decisions. (1) Gather information, (2) Consider values, (3) Explore consequences, (4) Make a
decision.
Earth as a System
Earth consists of rock, air, water and living things that all interact with each other. Scientists divide
this system into: (1) Geosphere, (2) Atmosphere, (3) Hydrosphere, (4) Biosphere
Geosphere –
The solid part of Earth that consist of all rocks and soil that extends form the center of the core to the
surface of the crust. The deepest well that has been drilled into Earth’s interior is only about 12 km
deep so alternative methods such as seismic waves are used to learn about the interior. Seismic
waves are the waves that travel through Earth’s interior during an earthquake. A seismic wave is
altered by the nature of material through which it travels. Seismologists measure changes in the
speed and direction of waves that penetrate the interior of the planet.
Compositional Layers – Earth is divided into 3 layers based on their chemical composition.
1. Crust – Thin outer layer composed almost entirely of light elements. The crust makes up less than
1% of the Earth’s mass and is the thinnest layer.
2. Mantle – Makes up 64% of the mass of the Earth and is made of rocks of medium density.
3. Core – Innermost layer composed of dense elements and makes up 1/3 of Earth’s mass.
Physical Layers – Earth is divided into 5 layers based on their physical composition.
1. Lithosphere – Rigid outer layer of the crust and the upper part of the mantle. It is divided into huge
pieces called tectonic plates.
2. Asthenosphere – The solid plastic layer of
the mantle that flows very slowly, which
allow tectonic plates to move on top of it.
3. Mesosphere - lower part of the mantle
4. Outer Core – Dense liquid layer is made of
nickel and iron.
5. Inner Core – Dense solid layer is made up
mostly of iron and nickel. It is solid because
of the enormous pressure. The temperature
is about 5,000oC.
Plate Tectonics – These plates are blocks of lithosphere that glide across the underlying
asthenosphere. The continents are locatd on tectonic plates and move with them. The major tectonic
plates include the Pacific, North America, South America, Africa, Eurasian and Antarctic plates.
 Plate boundaries – Most activity takes place at
the boundaries between the tectonic plates as
they move away from one another, collide with
one another or slip past one another. Enormous
forces are generated with these actions causing
mountains to form, earthquakes to shake the
crust and volcanoes to erupt.
 Where plates collide, the crust becomes thicker,
is pushed up and eventually forms mountain
ranges. (i.e. Himalaya Mountains in Asia began
to form when the Eurasian plate and the Indian
plate collided about 50 million years ago.)
Earthquakes – A fault is a break in the crust along
which blocks of crust slide relative to one another. When rocks break along the fault, a series of
ground vibrations occur causing an earthquake. Enormous movements of the crust can cause
widespread damage.
 The Richter scale is used by scientists to quantify the amount of energy released by an
earthquake. The measure of the energy released is called magnitude. The smallest magnitude
that can be felt is 2.0 and the largest magnitude recorded is 9.5.
Volcanoes – A mountain built from magma (melted rock) that rises from the Earth’s interior to its
surface forms a volcano. Majority of active volcanoes are located along tectonic plate boundaries that
surround the Pacific Ocean. Major volcanic eruptions can change Earth’s climate for several years.
Clouds of ash and gases enter the upper atmosphere and reduce the amount of sunlight that reaches
Earth. The reduction in sunlight causes a drop in average global surface temperature. (i.e. 1991
eruption of Mount Pinatubo in Philippines caused a 2-4% reduction of sunlight reaching
surface….average global temperatures dropped by several tenths of a oC over several years.)
Erosion – Water and wind continuously remove and transport rocks which results in erosion.
Atmosphere –
Earth is surrounded by a mixture of gases mostly found in the first 30 km above the surface that
constantly change as gases are added and removed. The atmosphere insulates the surface by
slowing the rate at which the Earth loses heat and maintains temperatures for life.
Atmospheric Composition - Nitrogen and oxygen make up the
majority of the gases. Other gases such as argon, carbon
dioxide, methane and water vapor make up less than 1%.
o Atmospheric dust, tiny solid particles of soil, salt, ash and
particulate matter, etc…are found in the atmosphere.
o Air becomes less dense as elevation increases, so
breathing becomes more difficult.
Atmospheric Layers - The atmosphere is divided into 4 layers
based on temperature changes that occur at different distances
above the Earth’s surface.
 Troposphere – The densest layer that extends to about 18
km above the Earth’s surface. Almost all the weather occurs in this layer and temperature
decreases as altitude increases.
 Stratosphere – Ozone (O3) in the stratosphere absorbs the sun’s ultraviolet (UV) energy reducing
the amount of UV radiation that reaches the Earth. Temperature also rises as altitude increases.
 Mesophere – The coldest layer with
temperatures measured as low as -93oC.
 Thermosphere – Nitrogen and Oxygen
absorb solar radiation, which results in
temperatures above 2000oC. Air is so thin
that particles rarely collide, so little heat is
transferred. We would not feel the heat! The
lower thermosphere is called the ionosphere
and absorbs X rays & gamma rays which
causes electrically charged atoms (ions).
Sometimes ions radiate energy as light.
Energy in the Atmosphere – Energy from the
sun is transferred in Earth’s atmosphere by 3
mechanisms: radiation, convection, conduction.
 Radiation – transfer of energy across space and in the atmosphere.
 Conduction – the flow of heat form a warmer object to a colder object when the objects are
placed in direct physical contact.
 Convection – transfer of heat by air currents. Hot air rises and cold air sinks.
Solar energy reaches Earth as electromagnetic radiation, which includes visible light, infrared
radiation and ultraviolet light. Earth receives about two-billionths of this energy. About ½ of the energy
that enters the atmosphere actually reaches the Earth’s surface.
In the troposphere, currents of less dense warm air rises into the atmosphere and currents of denser
cold air sink toward the ground. The continual
process of warm air rising and cool air sinking moves
air in a circular motion called a convection current.
Convection currents cause thunderstorms to form
when cold and warm air masses collide.
Greenhouse Effect – Sunlight penetrates the
atmosphere and the Earth’s surface radiates heat
back to the atmosphere. Some heat escapes into space, but some is trapped by the greenhouse
gases. Greenhouse gases absorb heat to maintain Earth’s temperature. The most abundant
greenhouse gases are water vapor, carbon dioxide, methane and nitrous oxide.
Hydrosphere
–
Salt water - Oceans covers about 70% of the Earth’s surface. Sunlight
heats the top 100 m of the surface zone and currents mix the heated
water with cooler water below. In the thermocline zone, water
temperature drops faster with increased depth. In the deep zone, the
temperature average 2oC. Oceans absorb and store energy from the sun
to regulate Earth’s temperature. Over half of solar radiation that reaches
Earth’s surface is absorbed by the oceans, but the process is lower than
on land. As a result, temperature changes much more slowly than it
would if there were no oceans on Earth. With no oceans, temperature
would be too extreme for life on Earth to exist.
Salinity of the ocean water is the concentration of all the dissolved salts
it contains. Salts have dissolved out of rocks on land and underwater
volcanic eruptions add salt. Salinity varies depending on rainfall and
evaporation rates.
Currents - Surface currents are wind driven
and result from global wind patterns. Surface
currents of the Pacific and Atlantic oceans
move in a clockwise direction north of the
equator, whereas surface currents flow in a
counterclockwise direction south of the
equator. Currents of warm water and currents
of cold water do not readily mix with one
another, so warm currents can flow for
hundreds of kilometers without mixing and
losing heat. Surface currents can influence
the climates of land areas they flow past.
Deep currents are stream-like movements of
water that flow very slowly along the ocean
floor. Deep currents form when cold, dense
water from the poles sink below warmer, less
dense water and flows toward the equator.
Fresh water – A little more than 3% of all the water on Earth is fresh water and the majority of fresh
water is found in icecaps and glaciers. River systems are streams that drain an area of land. When
water seeps into the ground it collects as groundwater which is about 1% of all the water on Earth.
Rock layers that stores and allows the flow of groundwater are called aquifer. The surface of the land
where water enters an aquifer is called a recharge zone.
Water Cycle - Water continuously moves through a
cycle. Evaporation is the process by which liquid water is
heated by the sun and then rises into the atmosphere as
water vapor. Condensation occurs when water vapor
forms water droplets on dust particles. These droplets
form clouds and when they become heavy, the droplets
fall as precipitation (rain, snow, sleet, hail).
Biosphere
–
The biosphere is a narrow layer of Earth’s surface in which life can exist. It’s made up of the
uppermost part of the geosphere, most of the hydrosphere and the lower part of the atmosphere. The
biosphere extends about 12 km into the ocean and about 9 km into the atmosphere. Most life requires
liquid water, moderate temperatures and a source of energy.
When an organism dies, its body is broken down and matter becomes available to other organisms.
However, energy must be supplied constantly because it doesn’t cycle. In a closed system, energy
enters and leaves the system, but matter does not. In an open system, both matter and energy are
exchanged between a system and the surrounding environment. Earth was once an open system as
matter in the form of comets and meteorites reached Earth.