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Our Changing
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EnvirOnmEnt
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TexTbook
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Our Changing Environment 2nd Edition Textbook
Philippine Copyright 2011 by DIWA LEARNING SYSTEMS INC
All rights reserved. Printed in the Philippines

Editorial, design, and layout by University Press of First Asia

No part of this publication may be reproduced or transmitted in any form or by any means electronic
or mechanical, including photocopying, recording, or any information storage and retrieval systems,
without permission in writing from the copyright owner.

Exclusively distributed by
DIWA LEARNING SYSTEMS INC
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Legaspi Village, 1229 Makati City, Philippines
Tel. No.: (632) 893-8501 * Fax: (632) 817-8700

ISBN 978-971-46-0189-5

Author
Edwehna Elinore P. Gayon holds a degree in Bachelor of Secondary Education major in
Chemistry Education and Master of Arts in Chemistry Education from the University of the
Philippines–Diliman (UP–Diliman). She is currently pursuing her degree in Doctor of Philosophy
in Chemistry Education at UP–Diliman. Ms. Gayon is an assistant professor at the UP–College
of Education and teaches undergraduate and graduate courses in general science and chemistry.
As part of her extension work, she conducts trainings for teachers in the different regions of the
Philippines. Recently, she has been involved in a collaborative research with the Faculties of
Education of Universiti Kebangsaan Malaysia and Sophia University. She has also presented
research papers in local and international conferences and has published articles both in education
and science education in local and international journals.

Consultant-Reviewer
Amelia E. Punzalan has a degree in Doctor of Philosophy in Chemistry Education and Master
of Arts in Chemistry from the University of the Philippines–Diliman. Currently, Ms. Punzalan is
a science education specialist of the University of the Philippines–National Institute of Science
and Mathematics Education Development (UP–NISMED).

PrEfaCE
Important changes are happening constantly in our environment. Most of these changes are
natural, some are biological, and others are chemical and geological. Some of these changes may
involve the exchanges of energy and materials among the different parts of the environment—air, land,
water, and life. One thing these changes have in common is that they all serve important purposes.
Our Changing Environment 2nd Edition is a book that tackles these constant changes. It uses
the socioecological approach, emphasizing the relationship between life, environment, and society.
For so long, natural changes favored life; lately, however, man-made changes have been straining the
capacity of the environment to support and sustain life on Earth. Now, the quality of the environment
has deteriorated so badly that the very quality of life has been adversely affected. The deterioration
of the environment is a global occurrence, and its effects—acid rain; air, water, and land pollution;
enhanced greenhouse effect and global warming; ozone depletion; and changing weather patterns,
among others—are life-threatening.
This book, which is divided into four units, aims to equip you with the scientific knowledge
necessary to understand fully the many changes in the environment. Unit I talks about the environment
you live in. It introduces you to basic concepts about the environment, which will help you understand
the succeeding lessons. Unit II deals with the air environment, particularly the air living things breathe.
Unit III focuses on concepts related to land and water. Unit IV talks about the interplay of energy, society,
technology, and environment.
This book also has seven useful components that will help you understand better the concepts
presented in each lesson. These components are the following:

• Related Life Experiences. This serves as a springboard for the lesson to be discussed. It lets you
reflect on specific situations or questions related to the lesson.
• The Helpers. This is a listing of important terms and their corresponding definitions.
• Bits and Pieces. This is a collection of facts and trivia relevant to the lesson.
• The Connections. This connects concepts tackled in the lesson with other subject areas or fields.
• Brain Exercise. This contains exercises and activities that will test your learning. It will also challenge
your critical thinking and analytical skills.
• Making It Real. This provides a challenging but enjoyable culminating activity.
• IT Link. This provides links to online articles that you can read so you can learn more about the
concepts discussed in the lesson.

At the end of the year, you will learn the many changes that occur in the environment. You will
be able to establish the links between and among these many changes. You will also have a better
understanding on how these changes affect life and the world at large. Furthermore, you will realize
how people—you included—have changed the world for the worse. You will become aware of how
people have contributed to the deterioration of the environment. More importantly, though, you will
learn how you can help stop this continuing deterioration. You will know how to reverse this life-
threatening trend so that life can continue to exist here on Earth.

tablE Of COntEnts

Unit I Our Living Environment
Chapter 1 Introduction
Lesson 1 Introduction to Environmental Science ..............................................................3
Lesson 2 Environmental Equilibrium and the Ecosystem..................................................8

Chapter 2 The Changing Biosphere
Lesson 1 Characteristics of the Biosphere ......................................................................16
Lesson 2 The Biosphere and the Past ............................................................................20

Chapter 3 Nutrient Cycles in the Biosphere
Lesson 1 Cycles in the Biosphere ...................................................................................32
Lesson 2 Carbon, Hydrogen, and Oxygen Cycles ..........................................................38
Lesson 3 Nitrogen, Sulfur, and Phosphorus Cycles ........................................................44

Chapter 4 Bioelements
Lesson 1 Essential Elements and Their Groupings.........................................................52
Lesson 2 Trace Elements and Bioselection Rules ..........................................................60

Chapter 5 Energy and Life Processes
Lesson 1 Photosynthesis.................................................................................................65
Lesson 2 The Food Chain ...............................................................................................74
Lesson 3 Energy and the Ecosystem ..............................................................................78

Unit II Our Air Environment
Chapter 6 The Changing Atmosphere
Lesson 1 The Atmosphere...............................................................................................84
Lesson 2 Atmospheric Phenomena.................................................................................95

Chapter 7 The Changing Quality of Air
Lesson 1 Added Substances in Air ................................................................................101
Lesson 2 Air Pollution in the Philippines........................................................................ 115

Chapter 8 Global Changes in the Atmosphere
Lesson 1 Revisiting the Greenhouse Effect .................................................................. 119
Lesson 2 Global Warming: Possible Scenarios .............................................................127
Lesson 3 Ozone Depletion ............................................................................................132

Unit III Our Water and Land Environments
Chapter 9 Earth’s Water Systems
Lesson 1 Water and Life ................................................................................................144
Lesson 2 Water around Us ............................................................................................145
Lesson 3 Properties of Bodies of Water ........................................................................156
Lesson 4 Earth’s Water and Climate .............................................................................159

Chapter 10 Meeting Water Needs
Lesson 1 Water Distribution and Uses ..........................................................................166
Lesson 2 Water Quality and Water Pollution .................................................................175
Lesson 3 Measuring and Improving Water Quality ........................................................187

Chapter 11 Making Soil Productive
Lesson 1 What Is Soil? ..................................................................................................194
Lesson 2 Soil Productivity .............................................................................................204

Chapter 12 Land Use and Misuse
Lesson 1 Land Use in the Philippines ...........................................................................213
Lesson 2 Deforestation..................................................................................................219
Lesson 3 Farming Practices ..........................................................................................225
Lesson 4 Mining Lands..................................................................................................227
Lesson 5 Solid Waste Problem......................................................................................230

Unit IV Energy, Society, Technology, and the Environment
Chapter 13 Burning Fuels
Lesson 1 Energy Conversions.......................................................................................235
Lesson 2 Energy Options ..............................................................................................246

Chapter 14 Energy Alternatives
Lesson 1 Solar Energy ..................................................................................................262
Lesson 2 Nuclear Energy ..............................................................................................264
Lesson 3 Geothermal Energy ........................................................................................278
Lesson 4 Nonconventional Energy Sources..................................................................281

Chapter 15 Sustainable Development
Lesson 1 Aspects of Sustainable Development ............................................................288
Lesson 2 Managing Resources and Population ............................................................299

Glossary .......................................................................................................................305
Bibliography .......................................................................................................................309
Index .......................................................................................................................313

UNIT I
Our Living Environment

C HAPTER 1 Introduction

Have you ever experienced extreme flooding in your neighborhood? How about
an abrupt rise or fall in temperature? What do you think may have caused these?
Why is it important to be aware of what is happening in your environment?

Fig. 1.1 Environment-friendly products and inventions

Plants, animals, air, water, and soil are around us; they form part of the environment we live in. We
also live in a world of social institutions, political organizations, and ecological diversity. In other words,
we live in a socioecological world, which is an integration of the natural world and the social world. As
such, science has played a major role in activities that provide more food, more materials, more energy
supply, and more livable space for people. However, the many applications of science have also played
a role in the environmental problems we face today. Despite this, science can still provide solutions to
these environmental problems. In fact, many scientists today are actively involved in developing clean
technologies and environment friendly materials.
Through the years, the growing concern for changes in both local and global environments
has been the focus of several environmental endeavors. One of these was the 1992 Earth Summit
or the United Nations Conference on Environment and Development held in Rio de Janeiro, Brazil.
The summit’s output, called Agenda 21, is a comprehensive program of actions to be adopted by the

2 OUR CHANGING ENVIRONMENT 2ND EDITION

governments who participated in the event. Agenda 21 emphasizes the need to change economic
activities based on a new understanding of the impact of certain activities on the environment. It
advocates the use of science in the sustainable development of Earth. The Earth Summit defined
sustainable development as the wise use of resources to meet the needs and wants of the present
without exhausting the limits of the ecosystem’s capability to support the living community and
without sacrificing Earth’s natural resources. In short, the Earth Summit emphasized resources
conservation and environmental protection.
A 10-year review of Agenda 21 during the World Summit on Sustainable Development was held
in Johannesburg, South Africa on September 2002. The review revealed that despite the efforts to
address environmental concerns, many of the goals laid out in 1992 remained unrealized. As a result,
a program called Education for Sustainable Development was emphasized as an essential vehicle for
empowering people to preserve the environment and build a sustainable future. In December 2002,
the United Nations General Assembly declared the years 2005–2014 as the Decade of Education for
Sustainable Development, with UNESCO as the lead agency in its implementation.
In May 2009, the 5th World Environmental Education Congress was held in Montreal, Canada with
the vision “Earth as our common home.” The event promoted the importance of taking care of Earth.
It called for people to change their attitudes and activities to preserve Earth’s natural resources.
The link between economic development and the wise management of environmental resources
is now generally accepted. Systematic environmental management requires balancing the use of
Earth’s resources and preserving them at the same time. These resources include land, water, minerals,
timber, and wildlife. Lakes, streams, rivers, seas, oceans, and underground water are examples of water
resources.
This book aims to give you a deeper understanding of the science of the environment. Knowing
about the environment using established scientific facts will let you care more about it. It is hoped,
therefore, that you will also be able to help protect and sustain Earth’s life-supporting capabilities.

Introduction to Environmental Science

What Is Environmental Science?
Organisms relate to one another through an array of interactions. These interactions are dynamic,
universal, and continuous, where cycles involving both living and nonliving things intersect. The
science that investigates the total relationships among living things and their nonliving environment
is known as ecology. Ecology was first defined in 1866 by German scientist Ernst Haeckel (1834–1919). The

OUR LIVING ENVIRONMENT 3

word ecology is derived from the Greek word oikos, meaning “a place to live.” Corollary, the application
of the knowledge of ecology to the management of the environment is called environmental
science.

The following is a more inclusive and holistic
definition of environmental science: It is the
systematic study of our environment and our place
in it. Environmental science is a multidisciplinary
The word environment comes
subject that applies knowledge from many scientific
from the French word environner,
disciplines. As you study ecological relationships,
which means to “encircle or
you may have to recall relevant concepts you have
surround.” It can be defined as
learned in other science courses, notably, biology,
• the circumstances and conditions
chemistry, physics, geology, and meteorology. Also
that surround an organism or a
integrated are information from other fields such as
group of organisms; or
agriculture, forestry, mathematics, engineering, and
• the social and cultural conditions
resource conservation and management. Furthermore,
that affect an individual or a
environmental science involves the social sciences such
community.
as sociology, economics, political science, demography,
geography, psychology, and ethics.
Scientific principles that are relevant to the study of the environment are not as straightforward
as those resulting from scientific investigations conducted in laboratories. Unlike scientific laboratories,
where conditions can be controlled and closely monitored, the environment is a complex system. Thus,
coming up with simple solutions to environmental problems can be extremely challenging.
A study of the environment becomes more meaningful when we place organisms in the core of
all relationships. We study the conditions, events, and influences that affect life and how life in turn
responds to these aspects. We are concerned with conditions that limit life, the use of resources by
living things, and the interaction of living things with their environment.
But what exactly comprises the environment of an organism? The total environment of an
organism includes all other forms of life on Earth and its nonliving environment. The nonliving
environment is made up of substances such as nitrogen, oxygen, water, carbon dioxide, calcium
carbonate, phosphates, and the organic by-products of the organism’s activities. It also includes
physical factors such as moisture, wind, tides, ocean currents, temperature, light, and topographical
factors such as altitude and slope.


This book will provide you a deeper understanding of the nature of the relationships that exist
between organisms and their environment. You will discover the great order in our environment and
the unforeseen negative impact of our activities on this very same environment. In all likelihood, the
general lack of concern for our environment stems from the lack of understanding of the delicate
relationships that exist in it. Are you aware that manipulating one part of the environment triggers a
series of events that can have serious effects on its other parts?

Studying an Ecosystem
In studying ecological
relationships, you should start by
focusing on a smaller system. A system
is any part of the environment that
is selected for the purpose of study.
You may be interested in studying a
pond, a decaying log, an aquarium,
a terrarium, or a field. Ecologists
may choose to study a grassland, a
forest, a river, or an ocean. These are
some examples of ecosystems. An
ecosystem or ecological system is
the basic functioning unit of nature. Fig. 1.2 In an ecosystem, a community of organisms interact with their
environment.
It consists of the nonliving (abiotic)
environment and the living (biotic) community it supports. These two components are intimately
linked by a variety of biological, chemical, and physical processes. The biotic and abiotic components
function together through an exchange of materials (matter) and energy.
There is an assortment of ecosystems to study. Ecosystems may be small or large, terrestrial or
marine, artificial or natural. No two ecosystems are exactly alike in composition, but there would be
ecological equivalents with comparable functions. Ecological equivalents are unrelated organisms
that occupy similar habitats and resemble each other. For instance, sharks (fish) and dolphins
(mammals) live in a marine habitat and they specifically resemble one another. Moreover, there are no
sharp boundaries between ecosystems. A river, for example, exchanges materials and energy with an
adjacent forest.


Consider the field of environmental
• An organism is any form of life.
chemical analysis. This field poses a major
Organisms are classified into species.
challenge to chemists for two reasons. First,
• A species is a group of organisms that
the properties of the environment change
resemble one another in appearance,
with time and in space. Many conditions
behavior, chemistry, and genetic
operate simultaneously within this complex
makeup. They can produce offspring of
natural system. Second, environmentally
their own kind.
significant concentrations of substances are
• The organisms in a given ecosystem form
usually at trace levels—in parts per
a community. Within the community,
million (ppm), sometimes even in parts per
organisms are grouped into populations.
billion (ppb) levels.
• A population is a group of interacting
Before the development of sensitive
organisms of the same species that
analytical instruments, chemical analyses of
occupy a particular space at a particular
environmental samples were very difficult, if
time.
not impossible, in certain cases. Such analyses
require meticulous preparation of the sample,
utmost cleanliness of glassware, skillful execution of the analytical procedure, and high sensitivity and
precision of the instruments used.
Other scientists conduct environmental studies in natural settings that require the use of
sophisticated instruments. For example, information about the thinning of the ozone layer has been
gathered using meteorological instruments mounted on airborne balloons. Another example is the
use of satellites to gather data about the surface of Earth and its oceans.

Fig. 1.3 Scientists at work on environmental studies


Environmental scientists can hypothesize about the behavior of environmental systems based on
previous observations and accumulated facts about the environment. They often resort to modeling
to come up with valid information about selected parts of the environment. Modeling of natural
phenomena is done using powerful computers. Modeling is an important tool in scientific studies as it
allows scientists to simulate complex systems.
You can also gather information about the environment from day-to-day observations or from
more formal environmental studies.

Units of Measure
Certain substances in the environment can exert significant effects even at concentrations you
may consider insignificant. To illustrate, just look at the amount of carbon dioxide (CO2) the air contains.
During the Intergovernmental Panel on Climate Change held in Fiji, Japan on June 2007, scientists
reported that the air contained 379 ppm CO2, which was based on data gathered in 2005. This means
that there are 379 cubic centimeters (cm3) of CO2 in 1 000 000 cm3 of air. This can be expressed in
percent or parts per hundred:

100
379 cm3 CO2 x = 0.0379%
1 x 106 cm3 air

In terms of mass per unit volume, 1 ppm is equivalent to 1 milligram per liter (mg/L).
Some substances have significant effects even at ppb level. Sulfur dioxide (SO2) in air, for example,
may be present at 50 ppb. This means that for every 109 cm3 of air, there are 50 cm3 of SO2. Sulfur
dioxide at 0.1 to 0.5 ppm can harm plants or cause respiratory illness in humans.

Did you know that since the Pre-Industrial Age (1790s–1860s), the amount of CO2
in the air has increased from 280 to 379 ppm (an increase of 35%)?


1. Why is it important to monitor the amount of gases such as CO2 and SO2 in the air?
2. If the concentration of carbon monoxide in the air is 5 ppm, how much is this in
a. percent?
b. ppb?

Environmental Equilibrium and the Ecosystem

Observe an object or a portion of the environment such as a piece of rock, a river, or a rice field.
Does it look exactly the same today as it was, for instance, a year ago? Do you think its properties
changed?

Environmental Equilibrium
The environment is constantly changing. These changes occur with time and in space. The
occurrence of change in the properties of an object or system is referred to as an event. Some events
occur very slowly such that the change may not be evident at once. Consider the wearing of rocks into
soil; this may take centuries to complete. Other changes such as the flash of lightning occur very fast.
More measurable changes are those that occur at intermediate rates.
All natural changes occur because of the tendency of systems to reach a state of balance or
equilibrium. A rice field may look the same each year during the same season when all the changes
taking place in it have reached a state of natural balance. When that happens, such a system has
reached environmental equilibrium.
Is the equilibrium established in a chemical system the same as the equilibrium attained in an
ecosystem?
Chemical equilibrium is described as dynamic, where opposing reactions occur at equal rates.
Environmental equilibrium, on the other hand, is steady state in nature and is established in an open
system. Steady-state equilibrium means the inputs and outputs to and from the system in terms of
energy or a given material are equal.


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