1. HigH ScHool Science Today
Second year
Textbook

2. HigH ScHool Science Today
Second Year
Textbook
Philippine Copyright 2009 by DIWA LEARNING SYSTEMS INC
All rights reserved. Printed in the Philippines
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ISBN 978-971-46-0099-7
reviewer
Annalee S. Hadsall has a bachelor’s degree in Biology (cum laude) from the Philippine Normal College.
She has a master’s degree in Botany, with specialization in Plant Systematics, from the University
of the Philippines−Los Baños under the UP-NSDB scholarship grant. Prof. Hadsall is an Assistant
Professor 7 at the Institute of Biological Sciences of the University of the Philippines–Los Baños. She
has been involved in writing laboratory manuals in biodiversity and general botany for UPLB and
biology modules for the UP Open University.

3. P r e fa c e
Discoveries in science and technology in recent years have had a profound impact on
our society. We are now able to communicate easier with the use of the Internet and cellular
phones. We have found ways to replace damaged body parts through prostheses and organ
transplants. People are continually developing new medicines to treat diseases that were
once fatal. Scientists have been able to clone animals, find alternative fuel sources, explore
the far reaches of outer space, and develop better materials for construction. Even the way
we entertain ourselves has been affected by discoveries in science.
With all these fascinating discoveries, it is important that you understand the
scientific principles behind such advancements. The High School Science Today series has
been developed with two objectives in mind: to explain key scientific concepts clearly and
accurately within a context of unifying themes; and to introduce you to the technology and
research techniques which have resulted from the application of these scientific concepts.
The topics in each textbook are organized to keep key science concepts in clear view.
In each chapter, you will find discussions on specific technological breakthroughs and the
implications these developments have on our global community.
Understanding science requires that you observe the things around you, perform
experiments to solve problems, and explain the reasons for your observation. Each
textbook contains activities that will help you develop the skills necessary in learning
science concepts meaningfully. These activities will provide you with hands-on learning
experiences. You will be asked to predict, hypothesize, describe, make models, form
conclusions, calculate, and measure with accuracy and precision.
As such, High School Science Today will enable you to keep pace with the ever-
evolving world of science and technology. We invite you to take this journey with us—into
the future and beyond.

4. Table of conTenTS
UniT 1 biology: THe Science of life
Chapter 1 Introduction to Biology
1.1 The Need to Study Biology .............................................................................................................. 2
1.2 The Different Branches of Biology .................................................................................................. 3
1.3 The Unifying Ideas in Biology........................................................................................................... 4
1.4 Living Things and Their Characteristics........................................................................................... 6
1.5 The Importance of the Scientific Method ........................................................................................ 9
1.6 The Scientific Way of Conducting Investigations ............................................................................ 11
Chapter 2 Technology and People
2.1 Biotechnology ................................................................................................................................... 15
2.2 Some Local and Foreign Biologists .................................................................................................. 18
2.3 Careers Related to Biology................................................................................................................ 21
Chapter 3 Tools Used in Scientific Studies
3.1 The Microscope ................................................................................................................................. 24
3.2 A Detailed Look at the Compound Microscope ............................................................................... 26
3.3 Other Tools Used in Scientific Research .......................................................................................... 29
UniT 2 THe PUzzle PieceS of life
Chapter 4 Cells in Living Things
4.1 Early Cell Discoveries........................................................................................................................ 32
4.2 The Different Parts of a Cell ............................................................................................................. 34
4.3 Organisms Can Be Unicellular, Colonial, or Multicellular .............................................................. 41
4.4 Prokaryotes and Eukaryotes ............................................................................................................ 43
Chapter 5 Passing across the Cell Membrane
5.1 The Fluid Mosaic Model of the Cell Membrane ............................................................................... 45
5.2 The Mechanisms for Cell Membrane Transport .............................................................................. 47
5.3 The Transport of Large Particles through Cell Membranes ............................................................ 50
5.4 Cell Size.............................................................................................................................................. 51
5.5 Research and Technology Related to Cells....................................................................................... 53
5.6 Importance of Some Cell Processes ................................................................................................. 54
UniT 3 ProceSSeS of bioenergeTicS
Chapter 6 What a Leaf Is
6.1 The Different Parts of a Leaf............................................................................................................. 58
6.2 Chloroplasts in Leaves ..................................................................................................................... 60
6.3 Chlorophyll in Plants ........................................................................................................................ 61
Chapter 7 The Process of Photosynthesis
7.1 The Photosynthetic Reaction ........................................................................................................... 64
7.2 The Light Reaction ........................................................................................................................... 65
7.3 The Dark Reaction ............................................................................................................................ 66
7.4 Factors Affecting Photosynthesis .................................................................................................... 69
7.5 Scientific Explanation of Farming Practices ................................................................................... 70
Chapter 8 Cellular Respiration
8.1 ATP..................................................................................................................................................... 74
8.2 The Process of Cellular Respiration .................................................................................................. 75
8.3 Interdependence among Living Things for Important Gases ......................................................... 79
UniT 4 THe organ SySTemS
Chapter 9 Hierarchy in Organisms
9.1 Levels of Organization...................................................................................................................... 84
9.2 Organized System ............................................................................................................................. 85
Chapter 10 The Organ Systems of Plants
10.1 Cell and Tissue Types Found in Plants ............................................................................................ 88
10.2 Factors Affecting the Growth of Plants ........................................................................................... 93
10.3 The Response of Plants to the Environment ................................................................................... 94

5. Chapter 11 Controlling and Regulating Body Systems
11.1 The Nervous System ......................................................................................................................... 97
11.2 The Different Sense Organs and Their Parts.................................................................................... 101
11.3 The Endocrine System ...................................................................................................................... 104
Chapter 12 Protective Body Systems
12.1 The Integumentary System .............................................................................................................. 111
12.2 The Muscular System ........................................................................................................................ 115
12.3 The Skeletal System .......................................................................................................................... 117
Chapter 13 Energy Producing and Distributing Systems
13.1 The Digestive System ........................................................................................................................ 121
13.2 The Respiratory System .................................................................................................................... 125
13.3 The Circulatory System ..................................................................................................................... 129
Chapter 14 Waste Elimination System
14.1 The Excretory System ....................................................................................................................... 133
UniT 5 reProdUcTive PaTTernS
Chapter 15 Division of Cells
15.1 The Cell Cycle and Mitosis ................................................................................................................ 140
15.2 Meiosis............................................................................................................................................... 144
15.3 Meiosis in Humans ........................................................................................................................... 146
Chapter 16 Plant Reproduction
16.1 Asexual Reproduction in Plants ....................................................................................................... 148
16.2 Sexual Reproduction in Plants ......................................................................................................... 150
Chapter 17 Animal Reproduction
17.1 Asexual Reproduction in Animals ................................................................................................... 158
17.2 Sexual Reproduction in Animals ..................................................................................................... 160
Chapter 18 Human Reproduction
18.1 The Male Reproductive System ....................................................................................................... 163
18.2 The Female Reproductive System..................................................................................................... 164
18.3 Fertilization ....................................................................................................................................... 166
Chapter 19 Problems and Issues Concerning Human Reproduction
19.1 Infertility .......................................................................................................................................... 172
19.2 Birth Control .................................................................................................................................... 173
19.3 Sexually Transmitted Diseases (STDs) ............................................................................................ 175
UniT 6 HerediTy
Chapter 20 The Chemical Basis of Inheritance
20.1 The DNA Molecule ............................................................................................................................ 180
20.2 The Role of Protein Synthesis in Inheritance .................................................................................. 182
20.3 DNA Replication ............................................................................................................................... 186
Chapter 21 Chromosomes and Genes
21.1 Mutation in Chromosomes and Genes ........................................................................................... 189
21.2 Human Chromosome Mutations Due to Nondisjunction ............................................................. 193
Chapter 22 Principles and Laws of Genetics by Mendel
22.1 Mendel’s Laws of Genetics ............................................................................................................... 196
22.2 The Use of Punnet Squares .............................................................................................................. 199
22.3 Genetic Reasoning ........................................................................................................................... 204
Chapter 23 Non-Mendelian Genetics
23.1 Other Types of Dominance .............................................................................................................. 208
23.2 Chromosomes Determine Sex ......................................................................................................... 211
23.3 Non-Mendelian Traits Involving Gender ........................................................................................ 212
Chapter 24 Effects of Environment and Technology on Heredity
24.1 Effects of the Environment on the Expression of Traits ............................................................... 217
24.2 Modern Technology and Genetics ................................................................................................... 219
UniT 7 HiSTory of living organiSmS
Chapter 25 Theories of Evolution
25.1 Some Theories of Evolution ............................................................................................................. 224
25.2 Patterns in Evolution ....................................................................................................................... 230

6. Chapter 26 Evidences of Evolution
26.1 Fossils ............................................................................................................................................... 232
26.2 Embryonic Development ................................................................................................................. 235
26.3 Biochemical Evidences ..................................................................................................................... 237
26.4 Effects of Technology on the Evolution of Organisms .................................................................. 243
Chapter 27 Human Evolution
27.1 Humans and Primates ..................................................................................................................... 246
27.2 Races .................................................................................................................................................. 250
UniT 8 claSSifying living THingS
Chapter 28 Milestones in Biological Classification
28.1 Basic Aspects of Taxonomy ............................................................................................................. 254
28.2 Different Levels of Classification .................................................................................................... 257
Chapter 29 The Six-kingdom Scheme of Classification
29.1 An Overview of the Six Kingdoms .................................................................................................. 261
29.2 Archaebacteria .................................................................................................................................. 263
29.3 Eubacteria ......................................................................................................................................... 263
29.4 Protista ............................................................................................................................................. 264
29.5 Fungi ................................................................................................................................................. 267
29.6 Plantae .............................................................................................................................................. 267
29.7 Animalia ............................................................................................................................................ 272
29.8 Viruses .............................................................................................................................................. 280
Chapter 30 Adaptive Mechanisms of Living Organisms
30.1 Adaptations of Animals ................................................................................................................... 286
30.2 Adaptations of Plants ...................................................................................................................... 288
30.3 Defense Adaptations ........................................................................................................................ 288
30.4 Adaptation for Preserving Offspring .............................................................................................. 291
Chapter 31 Some Organisms and Their Importance
31.1 Importance of Organisms................................................................................................................. 294
31.2 Conserving Economically Important Organisms ........................................................................... 295
UniT 9 Science in naTUre
Chapter 32 The Ecosystem
32.1 Ecosystem: An Interactive Community .......................................................................................... 300
32.2 The Ecosystem and Its Components ............................................................................................... 302
32.3 The Need for Natural Balance in an Ecosystem .............................................................................. 303
32.4 The Three Important Biogeochemical Cycles in an Ecosystem ...................................................... 303
32.5 Ecological Succession ....................................................................................................................... 307
Chapter 33 Interrelationships in an Ecosystem
33.1 Habitats and Lifestyles in a Community ......................................................................................... 311
33.2 The Different Biotic Relationships .................................................................................................. 312
Chapter 34 Energy Flow in an Ecosystem
34.1 Energy Supply .................................................................................................................................. 316
34.2 Energy Level ..................................................................................................................................... 316
34.3 Food Chains ...................................................................................................................................... 317
34.4 The Pyramid of Productivity ............................................................................................................ 319
34.5 Energy Requirement of Humans ..................................................................................................... 320
Chapter 35 Different Natural and Man-made Ecosystems
35.1 Terrestrial Biomes ............................................................................................................................ 323
35.2 Aquatic Biomes ................................................................................................................................. 326
35.3 Interdependent Ecosystems ............................................................................................................ 328
35.4 Man-made Ecosystems .................................................................................................................... 329
Chapter 36 Threats to the Ecosystems
36.1 Natural Threats ................................................................................................................................. 332
36.2 Man-made Threats ........................................................................................................................... 333
36.3 Saving Our Ecosystems .................................................................................................................... 337
Glossary .............................................................................................................................................................................. 341
Bibliography ............................................................................................................................................................................ 343
Index .............................................................................................................................................................................. 345

7. Biology:
Unit
1
The Science of life
Earth occupies a unique place in the solar system. Some scientists hypothesize that Earth is
the only planet that can sustain life.
Living things such as the forests, seas, grasslands, and man-made communities abound in
our planet. The study of life, therefore, has become a continuing human endeavor. This unit hopes
to inspire you to study Biology—the science of life.

8. Chapter 1
inTroducTion To Biology
Simply put, biology is the study of life. Anything living and to some extent, once-living,
fall under the domain of biology. This chapter will introduce the fundamentals of biology as a
scientific discipline as well as the general characteristics of living things.
1.1 The need To STudy Biology
Over the last few years, you have studied various organisms through their
characteristics. This is part of studying biology. You have also studied biology when you
identified the function of each major organ system in the human body. And it is biology
at work when you put food coloring in water to see capillary action in a lettuce stem. You
cannot get away from biology because you observe and participate in biological processes
every day as you eat, sleep, study, and play.
In an age when breakthroughs in the field of biological science are being made more
public, it is important that you, as a student, are aware of the implications of these recent
discoveries to society. But before you can begin to appreciate them, you should be able to
understand and learn the basic concepts involved in the study of life.
Fig. 1.1 We encounter biology every day.
High School Science Today II

9. 1 . 2 The differenT BrancheS of Biology
Biology is the study of life. It comes from the Greek words bios meaning “life” and
logos meaning “study.” Biology is divided into a number of specific fields of study. These are
the major branches of biology:
Biology
Botany is the Genetics is the Microbiology Evolutionary biology
study of plants. study of genes is the study of is the study of the
and patterns microorganisms change in organisms
of inheritance and viruses. over time.
(heredity).
Zoology is the Ecology is the study
study of animals. of relationships
between organisms
and their environment.
Here are some of the specific fields of Biology.
1. Anatomy − the study of the morphology (form and structure) of organisms and
their elements.
2. Bacteriology − the study of bacteria.
3. Biochemistry − the study of the molecules within the cell and the chemical
composition of living things.
4. Cytology − the study of the formation, structure, and function of cells.
5. Embryology − the study of the formation, early growth, and development of
organisms.
6. Entomology − the study of insects.
7. Epidemiology − the study of patterns of diseases within a certain population,
determining causes of diseases and how they spread.
8. Ethnobotany − the study of the way plants are identified, classified, and used by
various cultures.
9. Herpetology − the study of reptiles and amphibians.
10. Histology − the study of the minute structures of plant and animal tissues.
Biology: The Science of Life

10. 11. Ichthyology − the study of fishes.
12. Mammalogy − the study of mammals.
13. Marine ecology − the study of the interrelationships of marine organisms with
their environment.
14. Mycology − the study of fungi.
15. Ornithology − the study of birds.
16. Paleontology − the study of fossils.
17. Parasitology − the study of parasites.
18. Pathology − the study of the nature of diseases and their causes.
19. Phycology − the study of seaweeds and algae.
20. Physiology − the study of typical life processes, functions, and activities of
organisms.
21. Terrestrial ecology − the study of the interrelationships of land organisms with
their environment.
22. Virology − the study of viruses and viral diseases.
1 . 3 The unifying ideaS in Biology
Although the branches of biology deal with different fields of study, they share the
following principles:
1. Life on Earth is both diverse and united through continuous interactions among
life forms.
Recall the concept of the food chain and the food web you have learned.
All the organisms in the food web are connected to each other in a feeding
relationship. You can also be a part of the food web. How do you think this is
possible?
Similarly, people, animals, and plants are connected to each other in a
different way other than in a feeding relationship. Animals give off a gas which
plants need. Plants, in turn, release a gas which is necessary for the survival of
animals.
List some interactions between living organisms that you usually observe.
High School Science Today II

11. 2. The science of life can be studied through a variety of structural levels and
functions.
Even though living systems are complex, there is an underlying degree of
order which is basic to life. Your body is a very good example that shows the order
of structural levels. Your body is made up of organs. These organs are then made
up of smaller parts. Each part works together with other parts. Take eating as an
example. You use different body parts to chew and digest the food, but these parts
work toward a single function—to make the energy stored in food available for
your body to use.
3. The basic unit of structure and function is the cell, and as such it is at the core of
all levels of biological organization.
The cell is the basic unit of life. You will learn more about the cell in Unit II of
this book.
ACTIVITY 1.1 My Biology Collage
Materials
scissors, paste, old magazines, newspapers
Procedure
1. Make a collage showing the unifying ideas of biological sciences. You can use
pictures from old magazines.
2. On a clean sheet of paper, write a short paragraph explaining your artwork and
relating it with the unifying ideas of the biological sciences.
3. Share with the class what you have written. Explain the collage to the class.
Biology: The Science of Life

12. 1 . 4 living ThingS and Their characTeriSTicS
Can you tell if something is living or not? Things are said to be living if they have the
following characteristics:
• They are able to reproduce.
• They exhibit growth and development.
• They have the ability to respond to stimuli (irritability) and adapt themselves to
changing environmental conditions.
• They evolve.
• They have a high degree of organization.
• They undergo the process of metabolism.
• They exhibit homeostasis.
Reproduction
One distinction between living and
nonliving things is the ability of living things
to reproduce their own kind. Only living
things are capable of reproduction. Through
reproduction, the characteristics of the parents
are passed on from one generation to the next
generation.
What will happen if living things do not
reproduce?
Growth and Development
Living things exhibit growth and Fig. 1. The mating season marks the start of
development. A germinating seed grows and reproduction in some organisms.
develops into a plant. It increases in size, and
eventually forms distinct parts such as roots,
stems, and leaves.
An organism grows as its body processes food. Growth can be exhibited by an increase
in size, height, weight, or in the amount of materials in an organism. Development is
marked by the changes an organism undergoes throughout its life span.
High School Science Today II

13. This can be related to a human
being that started as a single cell
developing in a mother’s womb. From
that single cell, thousands of different
kinds of cells grew and developed.
Do nonliving things also exhibit
growth? How? Give an example.
Response to Stimuli (Irritability)
All living things are affected by
both internal and external factors. What Fig. 1. Physical changes are natural results of
happens to your body temperature when growth.
the weather gets cold?
Your brain responds internally to the
change in temperature by giving certain
signals to specific organs. You then respond to
the external factor, such as the cold weather,
by wearing a jacket or sweater.
Other living things also display the
ability to respond to stimuli. Take for example
the makahiya plant (Mimosa pudica), whose
leaves fold once you touch them.
What will happen to living things
if they cannot respond to changes in the
environment?
Fig. 1. Makahiya leaves fold once touched. It
takes about 10 minutes for the plant
to open its leaves again.
Evolutionary Adaptation
Response is basically a short-term reaction. However, since an organism’s
environment does not change drastically, organisms need to adapt. Evolutionary
adaptation refers to the traits an organism possesses as a consequence of surviving in the
environmental conditions.
Living things should adapt to their environment so that they will continue to exist.
Fish adapt to living in water. They have fins which enable them to maneuver and their body
shapes minimize the drag caused by swimming.
Biology: The Science of Life

14. All living things should adapt themselves to their habitats, climates, food sources, and
ways of life.
Phylogenetic Tree of Life
Bacteria Archaea Eucarya
Green
Filamentous Slime
bacteria Entamoeba molds Animals
Spirochetes
Methanosarcina Fungi
Gram Methanobacterium
positive Halophiles Plants
Proteobacteria
Methanococcus
Cyanobacteria
T. celer Ciliates
Thermoproteus
Planctomyces Flagellates
Pyrodicticum
Bacteroides Trichomonads
Cytophaga
Microsporidia
Thermotoga
Diplomonads
Aquifex
Fig. 1. One good way of showing relationships among organisms is by making a
phylogenetic tree. The phylogenetic tree shows how organisms diverged from
their common ancestor because of evolution. The phylogenetic tree above shows
the relationships among the major groups of organisms.
High Degree of Organization
In biology, scientists study life
and its processes following levels of
organizations.
The cell, the basic functional unit
of life, is a highly organized structure.
Cells are composed of biomolecules such
as nucleic acids, lipids or fats, proteins,
and carbohydrates. These biomolecules
help the cell perform essential
functions such as reproduction, atoms → molecules → organelles → cells
digestion, and respiration. organ system ← organs ← tissues
Different kinds of cells that are organism → population → community
grouped together make up a tissue.
Tissues are organized to form a more biome ← ecosystem
complex structure called an organ.
Organs that are grouped together form Fig. 1. All living things are made up of atoms which
form molecules. Molecules form larger
structures.
High School Science Today II

15. an organ system. Organ systems make up an organism. Each organ performs specific
functions necessary for the survival of an organism. The structure of an organ is developed
to suit a particular function. For example, your stomach has folded structures to increase
its surface area. A large surface area allows more food substances to be exposed to digestive
juices.
Metabolism
All living things obtain the materials and energy they need from the environment to
be able to perform the different life processes such as nutrition, movement, respiration,
excretion, growth, circulation, and reproduction.
Plants have the capacity to obtain and utilize light energy from the sun to convert raw
materials (carbon dioxide, water) into food. Animals and other living things are capable
of converting stored energy from food into a usable form of energy through cellular
respiration. Cellular respiration releases the stored energy from food like in plants. Energy is
then used by the cells to be able to perform various activities.
The process of converting and releasing energy is called metabolism. Only living
things are capable of undergoing metabolic activities. Metabolism enables living things
to break down food into simpler forms to release the stored energy in the process called
catabolism. Living things are also capable of anabolism which allows them to synthesize new
products such as proteins and nucleic acids.
Homeostasis
Living things have the ability to maintain the condition of their internal environment
within tolerable limits. This regulatory mechanism is called homeostasis. This is evident,
for example, in the regulation of body temperature in humans which is maintained at a
temperature of 37oC. If this temperature rises, the human body perspires. The evaporation
of perspiration cools the body.
1 . 5 The imporTance of The ScienTific meThod
As with all sciences, biology is not solely a visual experience—it requires all five senses
to collect, analyze, and use information. Like any field of study, biology requires patience
and systematic ways of solving problems.
Biology: The Science of Life

16. Scientists perform activities based on observation, data gathering and analysis, and
experimentation. The logical way used by scientists to solve their problems or to answer
their questions is called the scientific method. The method starts with the identification
of the problem. When scientists notice some occurrences in their surroundings, they start
to ask questions. They gather information about the problem from the previous works of
other scientists. Then, they come up with possible answers or hypotheses. Hypotheses
are intelligent guesses derived from observations. The hypothesis should contain the
problem or the subject being studied and two possible consequences or results. The two
possible consequences may be positive or negative. These consequences are used to denote
the possible result of the study. Hypotheses are tested by conducting experiments. The
organization and analysis of the experimental results follow after experimentation. Results
may be presented in graphs, charts, or tables. The results become the basis for a conclusion,
which might prove or disprove the hypotheses. The results of the scientific investigation
may be communicated to the scientific community through the publication of scientific
papers, conventions, symposiums, and conferences.
In summary, these are the steps of the scientific method:
1. State the problem.
2. Gather information about the problem.
3. Formulate a hypothesis.
4. Test the hypothesis through experimentation.
5. Analyze the data gathered from the experiment.
6. Formulate a conclusion.
7. Communicate the results.
Practice how to state a problem and formulate a hypothesis by doing the following
experiment.
ACTIVITY 1. Come into the Light
Materials
three Petri dishes, pond or aged tap water, three dozen planarians, three sheets of
white paper, three sheets of black paper, lampshade, and two shoe boxes
Procedure
1. Place the black and white sheets of paper under each Petri dish such that each
sheet is covered by half of the bottom of the dish.
2. Pour pond or aged tap water into each Petri dish.
10 High School Science Today II

17. 3. Place a dozen planarians in each of the Petri dishes.
4. Place two of the Petri dishes in two separate shoe boxes.
5. Focus the light of the lampshade on one of the Petri dishes.
6. Position all three dishes side by side. Observe the behavior of the planarians.
(a) (b) (c)
Questions
1. To which side of the dish did the planarians move?
2. How would you account for the movement of the planarians?
3. Which of the setups is experimental? Which is the control?
4. What are the variables used in the activity?
Check whether you have identified the variables correctly. Read the next lesson.
1.6 The ScienTific Way of conducTing inveSTigaTionS
Variables in a Scientific Investigation
You have learned the systematic way of solving problems. Now, you are ready to
observe other important factors involved in conducting a scientific investigation. The
factors affecting the results of a study are called variables. Variables are of two kinds:
dependent and independent. The factor that causes changes in the result of a study is called
the independent variable. The dependent variable is the result which is observed to
change due to the independent variable. In Activity 1.2, the movement of the planarians is
the dependent variable. The shoe boxes and light from the lampshade used for each dish are
the independent variables.
Biology: The Science of Life 11

18. In conducting a scientific investigation, there are always two kinds of setups—the
experimental and the control. The experimental setup is characterized by the presence
of independent variables which can be manipulated. This setup is the subject of your study.
In the case of the experiment in Activity 1.2, the Petri dishes in the shoe boxes and under
the lampshade are the experimental setups. The control setup is the one which does not
contain any independent variable and is the basis by which the experimental result should
be evaluated. Thus, one Petri dish with planarians was not exposed to changes in lighting
conditions to represent the normal situation.
From Activity 1.2, you have learned to identify the control and experimental setups.
Think of a problem with some help from your group mates. Design a simple experiment
based on the problem. Make an outline of your experimental design following the
scientific method. Identify the independent and dependent variables and the control and
experimental setups in your experiment.
You can always have two or more groups of setups while testing a single hypothesis.
What do you think is the significance of having several setups?
The outcome of scientific findings should be reported to the community through
publication of academic journals. The results of an investigation remain largely insignificant
to society unless reported.
Scientific investigations allow scientists to explore other fields of science, work with
different people, gain more knowledge, and learn and develop new ideas.
Chapter Review
I. Enriching Your Science Vocabulary
A. Choose the words in the box that will complete the sentences below.
bios entomology
logos herpetology
cell bacteriology
cytology
1. Scientists do not consider the virus as a living thing because it has no _____,
which is the basic unit of structure and function.
2. A scientist studying the life cycle of moths and flies to effectively limit their
population is a specialist in the field of _________________.
3. The word biology comes from the words _______________ meaning “life” and
_______________ meaning “study.”
4. Scientists who study the nature of microscopic organisms, especially bacteria,
are experts in the field of _______________.
1 High School Science Today II

19. 5. Scientists that specialize in cell structure, function, and processes are experts in
the field of ___________________.
B. Match the situations in column A with the characteristics of living things in column B.
Write the letter of your answer on the blank space.
Column A Column B
______ 1. Your heart is made up of a. reproduction
special kinds of muscles b. growth and development
working together.
c. irritability
______ 2. A flower that has been
d. metabolism
pollinated becomes a fruit.
e. organization
______ 3. You try to block very bright
light from your field of vision. f. evolution
______ 4. A mosquito lays thousands of
eggs in stagnant water.
______ 5. Your body breaks down food
so it can be used by your
cells.
II. Assessing Your Knowledge
A. Answer the following questions briefly.
1. Why do you think Biology is a required subject in high school?
2. Which branch of biology do you think is the most exciting? Why do you say so?
B. Choose the letter of the best answer. Write your answer on the blank space.
______ 1. Which of the following can be accepted or not depending on the
results obtained after the experiment?
a. variable
b. hypothesis
c. problem
d. conclusion
For numbers 2–5: Paulo wanted to show the relationship between plant growth
and the presence of fertilizer.
Problem: Will plants grow faster in soil with fertilizer?
Hypothesis: Plants grown in soil with fertilizer will grow faster than plants grown in
soil without fertilizer.
Biology: The Science of Life 1

20. E
xperiment:
a. Paulo got two young plants of the same kind, size, and vigor.
b. He placed equal amounts of loam soil in two identical containers. He planted
one plant in a container without fertilizer. He planted the other plant in a
container with fertilizer.
c. He placed the two plants in the garden, making sure that both plants get the
same amount of sunlight.
d. Every morning, he gave the plants the same amount of water.
e. He recorded the length of the stem of both plants for a week.
Data gathered after seven days:
Length of Stem (cm)
Setup
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Plant without
3 3.5 3.5 3.75 4 4.25 4.5
fertilizer
Plant with
3 3.5 4 4.25 4.75 5 5.5
fertilizer
______ 2. In the experiment, what is the independent variable?
a. application of fertilizer
b. amount of water given
c. length of the stems
d. number of days
______ 3. What is the dependent variable?
a. presence of fertilizer
b. amount of water given
c. length of the stems
d. number of days
______ 4. Which is the experimental setup?
a. plant with fertilizer
b. plant without fertilizer
c. two plants
d. fertilizer
______ 5. If Paulo were to base his hypothesis on the results, should he accept
his hypothesis?
a. Yes, the results of the experiment support his hypothesis.
b. Yes, the observations support the variable.
c. No, the results of the experiment do not support his hypothesis.
d. No, the observations are not enough to be conclusive.
1 High School Science Today II

21. Chapter 2
Technology and people
Technology refers to the practical application of knowledge to society. Scientists often
need to have a firm background on a body of knowledge before coming up with an invention
or an innovation.
Technology is the application of scientific principles. Many technological breakthroughs
and innovations have had significant implications on the way we live today. Can you imagine
how we can store food if the refrigerator were not invented? We have come to depend on the
benefits of technology. It is important that we understand the underlying scientific principles
behind them.
2.1 BioTechnology
Biotechnology is defined in two ways. First, it is concerned with the processing of
living organisms to produce useful products for human consumption. The second definition
refers to the technique of using deoxyribonucleic acid (DNA) sequence, cell, enzymes,
and other molecular components of a living organism to produce commercial products.
Biotechnology uses concepts in microbiology, biochemistry, and chemical engineering.
Biotechnology applies these concepts to manufacture useful products.
The first definition of biotechnology involves the production of useful products for
human consumption. Examples of these are the production of powdered shrimp heads, soy
sauce, patis and bagoong, nata de coco, and dairy products.
1. Powdered shrimp heads − The Philippines is one of the world’s major exporters of
shrimps, but exporters and processors face the problem of how to lengthen the
shelf life of their products. Shrimp heads release a foul odor because of the rapid
degradation of enzymes. Hence, exporters and processors remove the shrimps’
heads before they are exported. Not only does the foul odor affect the export
quality of the shrimps, but a great amount of shrimps’ heads is wasted. To be
able to maximize the use of shrimps, the Food and Nutrition Research Institute
(FNRI) has developed a technology that converts shrimps’ heads into a usable
product. This product is a concentrated powder which provides a good source of
protein and flavor for various food products.
2. Soy sauce − Traditionally, fermentation in soy sauce making lasts from 1 to 3 h
and requires a temperature of 37oC. However, recent studies have established
that good quality soy sauce needs to be fermented for a month at 40oC. Scientists
use the salt-tolerant acid bacterium, Lactobacillus delbrueckii. They have also
discovered that mongo beans are a good substitute for soy beans.
Biology: The Science of Life 1