HO CHI MINH UNIVERSITY OF INDUSTRY
INSTITUTE FOR ENVIRONMENTAL ENGINEERING & MANAGEMENT
Compiled by VO DINH LONG
ENVIRONMENTAL SCIENCES
(Specialized English course for Environmental Students)
HO CHI MINH CITY - 2006
CONTENTS
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CHAPTER 1: BASIC UNITS OF ECOLOGY
After studying this chapter, you should be able to:
1. Define environment.
2. Define an ecosystem.
3. Identify the components of the biosphere.
4. Describe the living and nonliving components of the environment.
5. Explain that bacteria and fungi are agents of decay.
6. Discuss the process of photosynthesis.
7. Enumerate the important factors that affect the growth of plants and the survival of animals.
1.1. THE ECOSYSTEM
When God created the world, He said, “Let the earth produces all kinds of plants, those that bear grain
and those that bear fruit”, and it was done. Then He also created animals, including human beings and
provided light. God, therefore, saw to it that everything needed for them to live is found in the world
which He created. He provided space, ways and means by with different organisms can interact with one
another and with their environment.
Part of the world where life operates is known as the biosphere.
The biosphere consists of the air (atmosphere), water (hydrosphere), and earth (lithosphere) where living
things interact with their environment.
Figure 1.1: The biosphere
When you study the interaction or relationship between organisms and their environment, you are
studying an ecosystem. The term ecosystem refers to all the living things and the nonliving things in a
given area. It includes all the plants and animals together with their surroundings. The ecosystem of an
aquarium, for example, consists of the hydrilla and others plants, fish, snails, and other aquatic animals,

bacteria. The abiotic component includes all the factors of the nonliving environment such as the
substratum, light, rainfall, nutrients, soil, and others. Both the biotic and abiotic components are equally
important in the ecosystem because without one of them the ecosystem would not function.
Insightfulness
The ecosystem consists of the biotic and abiotic components. The biotic components are the plants,
animals, and decomposers. The abiotic components are the non living factors, such as temperature,
water, and others. The abiotic affect the biotic components and vice versa.
1.2.1. Green plants
Green plants are known as the producers. They capture the energy from the sun and together with carbon
dioxide (CO
2
) in the air and water (H
2
O) convert together those into food energy. Since plants are able to
manufacture their own food, they are also known as autotrophs (or self-nourishing). These plants are able
to manufacture food though the process of photosynthesis, which will be explained in the next section.
Green plants also take substances, such as nitrogen and sulfur from the environment and convert those
into plant materials that can be used by other organisms as food. These green plants further provide
oxygen which is taken in by humans and animals in the process of respiration. For these reasons, all life,
whether in the pond, forest, or grassland, depend on green plants.
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You might think that green plants consist only of the trees or big plants that you see around. The other
producers are invisible to your eyes. These are the microscopic drifting plants which are greater sources of
food than the big plants that you can see. We call these microscopic plants phytoplankton. When they
become too abundant, they can give a pond or a body of water a green color.
Have you ever seen a pond or a lake with green surface?
Guide questions
1. What are producers?
2. What do producers perform in an ecosystem?
3. What are phytoplanktons?

fungi are known to be the fast-acting decomposers.
Decomposers are found everywhere. In the pond, they are abundant at the bottom where the remains of
the dead organisms (plants and animals) settle. On land, they abound on the surface of the soil where the
dead bodies of plants and animals are found.
Each of the three groups of the biotic component of the ecosystem - producers (plants), consumers
(animals), and decomposers (bacteria and fungi) - has its own specific function or task to perform.
Figure 1.5: Relationship among biotic component of the ecosystem
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The work performed by an organism is known as its ecological niche, while the place where the organism
lives in the ecosystem is known as its ecological habitat.
Guide questions
1. What are producers?
2. Give examples of producers?
3. What do decomposers perform in the ecosystem?
1.2.4. Nonliving factors
The nonliving factors of the environment make-up abiotic component of the ecosystem. These include the
chemical and physical factors in the environment, such as light, temperature, water, pH (acidity), wind,
chemical nutrients, salinity (saltiness), soil, and others. Organisms are affected by the biotic factors
simultaneously but, of course, different species of organisms are affected differently. For example, lichens
may not survive when temperature gets very high but cactus may.
Different organisms thrive in different conditions. There are animals, like the earthworms, which favor
wet condition, while others, like ants, prefer drier conditions. Some plants, such as cactus, grow best in
sandy soil while tomatoes grow best in loamy soil.
As a whole, these environmental factors not only provide essential energy and materials but also
determine the kind of organisms that will inhabit the area. Hence, they provide the conditions necessary
for the survival of the organisms.
Guide questions
1. What are the components of an ecosystem?
2. Give examples for each component of the ecosystem.
3. In general, what are the functions of these components?

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Decomposer (also known as microconsumer): Organism which breaks down nonliving organic material;
example are bacteria and fungi.
Environment: Sum of all external forces and conditions acting on an organism or a community of
organisms.
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CHAPTER 2
MATERIALS AND NUTRIENT CYCLES
The energy that flows into an ecosystem cannot be recycled. Once the energy is used, it is lost. But it
much be constantly repeatedly replenished if the ecosystem is to continuously function.
The important chemical nutrients, however, are used repeatedly. They are cycled between the living and
nonliving components of the ecosystem. Generally, they begin in the abiotic part of the ecosystem (water,
land, and air). Then, they enter to the bodies of plants and animals and return into the abiotic environment.
The movement of these materials and nutrients between the living and nonliving environment clearly
shows the interrelatedness of the abiotic and biotic components in an ecosystem. Among these recycled
materials and nutrients are carbon, oxygen, water, nitrogen, and phosphorus.
After studying this chapter, you should be able to
1. Identify different nutrients that can be recycled.
2. Explain the water, carbon and oxygen, nitrogen, and phosphorus cycles.
3. Discuss the importance of each of these cycles.
4. Discuss how people affect these cycles.
5. Differentiate micronutrients from macronutrients
2.1. IMPORTANCE OF THE NUTRIENT CYCLES
The energy from the sun flows to the plant goes to the herbivore that eats the plant, to the carnivore, and
to the last consumer until the energy is lost into the ecosystem. The energy does not go back to the source.
It cannot be used over and over again.
In contrast, when the bodies of dead plants and animals decompose, they are changed into nutrients
through the action of bacteria and fungi. The nutrients are stored in the abiotic environment like the soil.
The nutrients can be used again by the plants. The plants are eaten by the animals and when the animals
die, they decompose into nutrients. These nutrients can be used over and over again. In this way, a cycle

2.2 THE WATER CYCLE
As with any cycle, the water cycle has neither beginning nor end. However, it is useful to choose a
starting point. Let us begin with water vapor in the atmosphere.
a)
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b)
Figure 2.1: The water cycle
When water in the atmosphere reaches saturation (the highest amount of moisture that the air can hold), it
falls as rain. This falls directly to the land and bodies of water like the oceans and seas. Some runs off the
surface of the land into rivers. The rain that falls on the land is absorbed by plants through the roots and
drank by animals. Some penetrates the soil and becomes part of the underground water, which eventually
empties into the oceans. The processes of condensation and precipitation are responsible for the return of
water from the atmosphere into the land and other bodies of water.
The water from the land and other bodies of water returns to the atmosphere through the process of
evaporation. Plants return the water by the process known as transpiration, while animals do this through
respiration. Water accumulates again in the atmosphere as clouds and falls as rain.
Guide questions
1. What is saturation?
2. What is evaporation?
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3. What is respiration?
4. Trace the pathway of the water cycle.
2.3. THE CARBON AND OXYGEN CYCLE
Much of the carbon in the environment exists in the form of carbon dioxide. Plants absorb this gas though
the leaves and use in the process of photosynthesis. Oxygen is given off during this process. Animals and
other consumers obtain their food as well as their oxygen needs from plants. In the process of respiration,
the food is broken down into CO
2
and water which are returned into the atmosphere.
Figure 2.2: The carbon and oxygen cycles

5. What two important processes are involved in the cycle of carbon and oxygen? Discuss these
processes.
2.4. THE NITROGEN CYCLE
Nitrogen is an element crucial to life. It is an important component of proteins and nucleic acids. The
nitrogen gas constitutes about 78 percent of the air in the atmosphere. However, it cannot be used directly
by plants and animals. Plants use it in the form of nitrates.
You inhale large quantities of nitrogen but it remains in your body unchanged.
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Figure 2.3: The Nitrogen Cycle
Nitrogen in the atmosphere is converted into nitrates in two ways: (1) by the action of lightning and (2) by
action of specialized organisms. Electrical activity (lightning) during thunderstorms converts nitrogen into
nitrates but only a small amount. The nitrates produced by this process fall to the earth with the rain.
The organisms that convert nitrogen are bacteria, algae, and fungi, of which bacteria is the most
important. Nitrogen-fixing bacteria directly convert nitrogen into nitrates though the process called
nitrogen fixation. Examples of nitrogen-fixing bacteria are the Rhizobium, which live in the roots of
legumes like beans, peas, and peanuts. The association between Rhizobium and legumes forms swollen
areas within the roots called nodules. Nitrates are formed within the nodules. The compounds are then
used by the plants to build proteins, or remain in the soil as fertilizers. Because of this, legumes are
important crop rotation as they help maintain soil fertility. This explains why farmers plant legumes in
soil before they plant new crops.
Decomposers break down the protein in the bodies of plants, animals, and their wastes. In this process,
ammonia is produced. Ammonia may be used directly by some plants but others cannot. They have to
transform this into nitrates through the nitrogen-fixing bacteria. This process converting ammonia to
nitrates is known as nitrification. The plants are then able to obtain nitrates to synthesize amino acids and
proteins.
The nitrates produced by the nitrogen-fixing bacteria are converted into nitrites by another group of
bacteria called nitrite bacteria. Nitrites are converted into nitrogen by the denitrifying the bacteria in a
process called denitration. Denitration completes the cycle of nitrogen.
Insightfulness
- The most complex of the nutrient cycles is the nitrogen cycle. It involves many microorganisms.

sediments are recycled back to the soil by means of upwelling. If upwelling does not take place, the
phosphate becomes incorporated into the phosphate rocks.
Phosphate rocks are mined to be used in the manufacture of phosphate fertilizers. Though leaching, the
phosphorus in these fertilizers is lost from the soil. Human therefore hasten the rate of loss of available
phosphate. This can have serious effects on the supply of phosphorus for agriculture in the future.
Insightfulness
- Phosphorus presents in soil in the form of phosphates. Though weathering, phosphate rocks
contribute to the amount of phosphate in the soil.
- Phosphate is taken in by plants and passed on the food chain. When plants and animals die, the
bacteria convert the dead bodies into phosphates and return them into the soil.
- Guano deposits are good sources of phosphates.
Human activities have altered the cycle of materials in the environment. When people cut down trees or
destroy forest in one area, rainwater continues to flow until it finally reaches the sea instead of rising to
the atmosphere and falling again on the forests. The massive destruction of the forests changes the
environmental conditions, so that forests may never recover at all.
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Figure 2.5: Eutrophication
Similarly, deforestation also affects the mount of nitrates in the soil though leaching. This loss of nitrogen
limits the growth of plants and pollutes groundwater.
The phosphorus cycle has also been disrupted by the activities of humans especially in the water
ecosystem. People use a lot of agricultural fertilizers and detergents of which phosphates are major
components. When the phosphates from fertilizers and detergents run off into lakes, they stimulate the
rapid growth of algae and other aquatic plants causing algae bloom. This condition is known as
eutrophication.
As the plants age and die, decomposition takes place and use up so much oxygen causing the death of fish
and other animals.
Guide questions
1. What is the importance of phosphorus?
2. What processes are involved in the cycle of phosphorus?
3. In what ways have people altered the cycle of nutrients in the environments?

6. Enumerate some bad effects of modern technologies.
3.1. BALANCE OF NATURE
Scientists estimated that the earth is already around three billion years old, and it will exists for another
three billion years. The life of the earth depends mainly on the sun. If the gravitational pull of the sun
remains constant, the earth will continue to revolve around the sun in its present speed. There is a delicate
balance between the centrifugal force of the earth as is goes around the sun.
If the sun continue to shine the way it is now, then the earth will continue to receive radiant energy needed
by the living creatures. Again, there is a delicate balance here. Too much sunshine will make the earth too
hot for most living beings to survive. In short, the balance of nature is so delicate that any action that
might upset such balance could have catastrophic results.
For millions of years, this balance of nature has been maintained. The animals that antedated humans for
thousands of year did not really disturb the environment. The effect they made on the environment was
minimal and Mother Nature easily recovered.
During the dawn of civilization, humans and the predators lived in very similar ways. Both hunted for
food and dwelt in natural habitats, like caves. With this kind of life, they did not alter the environment.
But, since humans were more intelligent and more cunning, plus the fact that they walked erect and made
use of their hands, they were able to invent weapons to help them. Axe from stones and spears from sharp
object made them better hunters than the animals. And when they learned the use of fire, they cooked their
food with it, warmed their bodies by it, and heated a lot of things to help them survive. That was when
humans proved their superiority over animals.
When they learned to eat green leafy vegetables and learned how to cultivate them, they started to alter
the environment. They made clearings in the forests and planted vegetables. When the land was no longer
that fertile, they abandoned the place and cleared other lands. That was the beginning of forest
destruction. Then they learned how to domesticate animals and lived in a permanent dwelling which was
made of the products of the environment, like wood for the structure and leaves for roofing. They had to
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change the environment some more. Fortunately, there were not so many people at that time, so the
environment was able to recover. The balance of nature remained.
As the population increased and the needs of people became more complex, they put greater and greater
pressure on the environment. Larger houses were constructed from different materials, strong fences to

population increase.
In the field of animal science, researchers were able to improve the breed of animals used for food. Faster-
growing chickens and pigs and cultured fish are some good examples. Artificial hatching of eggs was
invented. All these resulted in more food for the fast-growing population of the world.
In the field of engineering, scientists invented better means of transportation on land, at sea, and in the air.
The more recent inventions include the bullet train that can run up to 500 kilometers (km) per hour,
airplanes that can carry up to 700 passengers, and large ships powered by nuclear fuel.
Landscapes have been altered to improve services to the people. For instance, dams were built to produce
electricity for homes and factories. Oil, coal, and other fossil fuels were mined to power these new
inventions.
For more comfort at home, scientists invented artificial lighting, air-conditioning systems, refrigerator to
preserve food better, radio and television for faster and better dissemination of information and for
entertainment, and all those electric gadgets in the kitchen to the delight of many housewives.
In the field of food technology, we can choose from a very wide variety of food available in the market,
caned goods of all kinds, powered milk, packed lunches, preserved fruits and vegetables, and many others.
All there may be considered as the good impact humans have made on the environment. As a result of
these inventions and new technology, people are living better food, live in more comfortable homes, enjoy
their vacations more, get better health services, travel faster, and dress better. In short, they can do a lot
better than their ancestors.
3.3. ADVERSE EFFECTS OF PEOPLE’S ACTIVITIES
Humankind’s intervention with nature has its adverse effects too. These include the pollution produced by
modern technology and its ill effects on the environment (disruption of the atmosphere which causes
greenhouse effect, ozone depletion and acid rain); among others; pollution of the water system,
deforestation, improper disposal of solid wastes, as well as nuclear wastes; and noise pollution.
3.3.1. The greenhouse effect
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Figure 3.1: The greenhouse effect
Too much carbon dioxide and other gases emitted by factories are accumulating in the atmosphere. These
gases allow sunlight to penetrate the earth’s atmosphere but unfortunately, they also trap radiant heat and
revert its escape into outer space.