enquiry into life - sylvia mader

8/12/2019 Enquiry into life - sylvia Mader

1/16

1

The Study of LifeChapter Concepts

1.1 The Scientific Process The scientific process allows biologists to gather

information and come to conclusions about thenatural world. 2

Various conclusions pertaining to the same areaof interest are sometimes used to arrive at atheory, a general concept about the naturalworld. 5

All persons have the responsibility to decidehow scientific information can best be used tomake ethical or moral decisions. 6

1.2 The Characteristics of Life Although life is quite diverse, it can be definedby certain common characteristics. 7

The biosphere is made up of ecosystems whereliving things interact with each other and thephysical environment. 10

The biodiversity of the biosphere is beingthreatened by human activities. 12

1.3 The Classification of Living Things

Living things are classified into categoriesaccording to their evolutionary relationships. 13

Many biological experiments are performed in the laboratorywhere conditions can be more easily controlled.

Back Forward Main Menu TOC Study Guide TOC Textbook Website Student OLC MHHE Website
http://toc.pdf/http://toc.pdf/


2/16

1.1 The Scientific ProcessBiology is the scientific study of life (Fig. 1.1). Religion, aes-thetics, ethics, and, yes, science, are all ways that humanbeings have of finding order in the natural world. But sci-ence differs from other human ways of knowing and learn-ing by its process.

The process of science is unique. Science is a humanendeavor that considers only what is observable by the sens-

2 Introduction 1-2

About 200 years ago, an English country doctor,

Edward Jenner, made medical history due to a keen

observation. He noticed that milkmaids usually avoid-

ed contracting smallpox, a disfiguring and frequently fataldisease. Jenner reasoned that the women were somehow

protected because they had previously had cowpox, a simi-

lar but much less serious illness. To test that hypothesis,

Jenner injected a young boy with cowpox, and later

exposed him to smallpox. When his volunteer remained

healthy, the way was paved for the development of the mod-

ern version of a smallpox vaccine that has done away with

the disease entirely.

Biology uses the same methodology today as was used

by Jenner to come to conclusions that are accepted untilproven false by future investigations. The information pre-

sented in this text is the result of work done by scientists

over the ages. What is science and what methodology does

science use?

Figure 1.1 Diversity of life.Biology is the scientific study of life, which has diversified into the many forms we find on planet Earth. a.Vorticella, a protozoan; b. Hibiscus, a

flowering plant; c. Sally lightfoot, a crab; d. Snow leopard, a mammal

es or by instruments that extend the ability of the senses.Microscopes extend the ability of sight way beyond whatcan be seen by the naked eye, for example. Observations canbe made by any one of our five senses; we can observe withour noses that dinner is almost ready; observe with our fin-gertips that a surface is smooth and cold; and observe withour ears that a piano needs tuning. Various input allows sci-entists to formulate hypotheses.

Formulating a HypothesisOnce a scientist becomes interested in an observable event,called a phenomenon,he or she will most likely study up on

it. The goal will be to find any other past work in the area;the Internet, the library, other scientists will all be consultedto see what past ideas there may have been about this phe-nomenon. All of this input helps a scientist use imaginationand creative thinking to formulate a hypothesis. A hypothe-sis is a tentative explanation of a scientific question based onobservations and past knowledge.

Hypotheses, of course, vary in the level of their sophis-tication. A young person in elementary school mighthypothesize that plants need light in order to grow; while ahigh school student might hypothesize that light allowsplant leaves to produce sugar. In any case, all the past expe-riences of the individual no matter their source, will mostlikely influence the formulation of a hypothesis. Einsteinsaid that aesthetic qualities like beauty and simplicity

30 m

d.Snow Leopard, a mammal

a.

Vorticella, a protozoan

b.

Hibiscus,a flowering plant

c.

Sally lightfoot, a crab

http://sgch01.pdf/http://sgch01.pdf/http://glossary.pdf/http://glossary.pdf/http://sgch01.pdf/http://glossary.pdf/http://glossary.pdf/


3/16

helped him to formulate his hypotheses about the workingsof the universe. Indeed, most every scientist looks favorablyupon the simplest hypothesis for a phenomenon and teststhat one first.

Science only considers hypotheses that can be tested.Moral and religious beliefs while very important to our livesdiffer between cultures and through time and they are notalways testable by further observations and/or experimen-tation.

Testing a HypothesisHypotheses are tested either in the laboratory setting or in

a natural setting. The laboratory is a place that lends itselfto carrying on experiments,which are artificial situationsdevised to test hypotheses. Experiments can also be car-ried out in a natural setting, called the field. David P.Barash, who was observing the mating behavior of moun-tain bluebirds, decided to perform an experiment to testthe hypothesis that aggression of the male varies accord-ing to the reproductive cycle. He posted a male bluebirdmodel near nests while the resident male was out forag-ing. The behavior of the male toward the model andtoward his female mate were noted during the first tenminutes of the males return. Aggression was most severewhen the male model was presented before the first eggwas laid, less severe when the model was presented afteran egg was laid, and least severe after the eggs hadhatched (Fig. 1.2).

Laboratory experiments are often preferred to experi-ments in the field because a laboratory setting eliminatesextraneous variables. A variable is a factor that can cause an

observable change during the progress of the experiment.The Science Focus on the next page describes a hypotheticalexperiment scientists conduct to determine whether sub-stance S is a safe food additive. Some of the possible vari-ables include the individual characteristics of the mice,availability of food and water, and environmental condi-tions such as the cleanliness of the cages and the tempera-ture and humidity of the room, and so forth. Theexperimenters would try to keep all these variables constantexcept the presence or absence of substance

Experiments are considered more rigorous when theyinclude a control group. Control in this context does notrefer to the power of the experimenterrather it refers tothe validity of the experimental results. A control groupexperiences all the steps in the experiment except for theone that is being tested. Barash used a control group. Heposted a male robin instead of a male bluebird near certainnests. (The male bluebirds did not respond at all to a robinmodel.) In the substance S experiment, the mice in the con-

trol group do not have substance S added to their food.When an experiment has a control group, we know that theresults are due to the variable being tested and not due tosome nonidentifiable chance event that occurred during theexperiment.

Chapter 1 The Study of Life 31-3

Stage of Nesting Cycle

ApproachesperMinute

nestconstruction

0.5

1.0

1.5

2.0

approaches tomale model

approaches to

female birdnest 1nest 2

key:

0first egg

laidhatching of

eggs

c. Scientist studies results and comes to a conclusion.

b. Scientist performs experiment and collects objective data.

a. Scientist makes observations, studies previous data, and formulates a hypothesis.

Figure 1.2 Example of scientific method.Observation of male bluebird behavior allowed David Barash to

formulate a testable hypothesis. Then, he collected the datadisplayed in a graph and came to a conclusion.

http://glossary.pdf/http://glossary.pdf/http://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001al.pdfhttp://vrl/0001al.pdfhttp://vrl/0001bl.pdfhttp://vrl/0001al.pdfhttp://glossary.pdf/http://glossary.pdf/


4/16

Biologists want to determine if sweetener S is a safe food addi-tive and design a controlled laboratory experiment. They place

a certain number of randomly chosen inbred (genetically simi-

lar) mice into the two groupssay, 100 mice per group

(Fig. 1A). If any of the mice are different from the others, it is

hoped random selection will distribute them evenly among the

groups. The researchers also make sure that all conditions, such

as availability of water, cage setup, and temperature of the sur-

roundings, are the same for both groups. The food for each

group is exactly the same except for the amount of sweetener S.In experiment 1, the researchers formulate a hypothesis that

sweetener S is a safe food additive at any dietary intake. The

control group receives no sweetener S and in the test group 50%

of the diet is sweetener S. At the end of the experiment, both

groups of mice are examined for bladder cancer. They find that

one-third of the mice in the test group have bladder cancer,

while none in the control group have bladder cancer. The results

of this experiment falsify the hypothesis and the researchers

conclude that sweetener S is not a safe food additive at 50% ofdietary intake.

The researchers decide to refine their study, and in experiment

2 they hypothesize that sweetener S is safe if the diet contains a

limited amount of sweetener S. They feed sweetener S to groups of

mice at ever-greater concentrations until it reaches 50% of the diet.

Group 1: diet contains no sweetener S (the control)

Group 2: 5% of diet is sweetener S

Group 3: 10% of diet is sweetener S

ZGroup 11: 50% of diet is sweetener S

The researchers present their data in the form of a graph and

statistically analyze their data to determine if the difference in

the number of cases of bladder cancer between the various

groups is significant and not due to simple chance. Finding that

they are significant, the researchers conclude that they can now

develop a recommendation concerning the intake of sweetener

S in humans. They suggest that an intake of sweetener S up to

10% of the diet is relatively safe but thereafter an ever-greaterincidence of bladder cancer should be expected (Fig. 1A).

A Controlled Laboratory Experiment

Figure 1A Design of a controlled experiment.

Genetically similar mice are randomly divided into a control group and (a) test group(s) that contain 100 mice each. All groups are exposedto same conditions, such as cage setup, temperature, and water supply. The control group is not subjected to sweetener S in the food. At

the end of the experiment, all mice are examined for bladder cancer.

Test group: sweetener in food

Control group: no sweetener in food

Bladder cancerexamination

Experiment 1

control group: no bladder cancertest group: one-third of mice have bladder cancer

Sweetener S in food (%)

Mice

withbladdercancer(%)

10

15

20

25

30

0

10 20 30 40 50

Experiment 2

http://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdfhttp://vrl/0002l.pdf


5/16

The Experimental ResultsThe results of an experiment are referred to as the data.Dataoften takes the form of a table or a graph that allows one to

see the results in an organized manner. Barashs data areshown in Figure 1.2. Data should be objective rather thansubjective, and mathematical data are conducive to objectiv-ity. For example, Barash didnt report that it seemed to himthat the male bluebirds were more aggressive before theeggs were laid (subjective); rather, he defined aggression asthe number of approaches per minute (objective) andreported that number. When Mendel, the father of genetics,did a pea cross concerning height, he didnt report that he

could tell at a glance there were more tall than short plants;he reported that the ratio was three tall to every short plant.In fact, Mendel repeated one particular experiment so manytimes that he counted 7,324 peas!

To ensure that the results are not due to chance or someunknown variable, experiments are often repeated not onlyby the original scientist but by others in the same area ofexpertise. Therefore, scientists must keep careful records ofhow they perform their experiments so that others canrepeat them. If the same results are not obtained over and

over again, the experiment is not considered valid.

The ConclusionAfter studying the results, the experimenter comes to a con-clusion whether the results support or falsify(show to beuntrue) the hypothesis. The data allowed Barash to con-clude that aggression in male bluebirds is related to theirreproductive cycle. Therefore, his hypothesis was support-

ed. If male bluebirds were always aggressive even towardmale robin models, his hypothesis would have been provenfalse.

Science progresses and the hypothesis may have to bemodified in the future. There is always the possibility that amore sophisticated experiment using perhaps moreadvanced technology might falsify the hypothesis. There-fore, a scientist never says that the data prove the hypoth-esis to be true. Because of this feature, some think ofscience as what is left after alternative hypotheses have been

rejected.Scientists report their findings in scientific journals so

that their methodology and results are available to the scien-tific community. Barash reported his experiment in the

American Naturalist.1 The reporting of experiments results inaccumulated data that will help other scientists formulatehypotheses. Also, it results in a body of information that ismade known to the general public through the publishing ofbooks, such as this biology textbook.

Scientific TheoriesThe ultimate goal of science is to understand the naturalworld in terms of scientific theories, which are concepts that

join together well-supported and related hypotheses. In amovie, a detective may claim to have a theory about thecrime. Or you may say that you have a theory about thewon-lost record of your favorite baseball team. But in sci-ence, the word theory is reserved for a conceptual schemethat is supported by a broad range of observations, experi-ments, and data.

Some of the basic theories of biology are:

Name of Theory ExplanationCell All organisms are composed

of cells.

Biogenesis Life comes only from life.

Evolution All living things have acommon ancestor and areadapted to a particular wayof life.

Gene Organisms contain codedinformation that dictatestheir form, function, andbehavior.

Evolution is the unifying concept of biology because it per-tains to various aspects of living things. For example, thetheory of evolution enables scientists to understand the his-tory of life, the variety of living things, and the anatomy,physiology, and development of organismseven their

behavior.Barash gave an evolutionary interpretation to his

results. It was adaptive, he said, for male bluebirds to be lessaggressive after the first egg is laid because by that time themale bird is sure the offspring is his own and maladaptivefor the male bird to waste time and energy being too aggres-sive toward a rival and his mate after hatching because hisoffspring is already present. (When an organism is adaptedto its environment, it is better able to survive and produceoffspring.)

Fruitful theories are ones that help scientists generatenew hypotheses, and the theory of evolution has been avery fruitful theory. In fact, it probably helped Barashdevelop the hypothesis he chose to test. Because the the-ory of evolution has been supported by so many obser-vations and experiments for over 100 years, somebiologists refer to the principleof evolution, suggestingthat this is the appropriate term for theories that are gen-erally accepted by an overwhelming number of scien-

tists. The term law instead of principle is preferred bysome. In another chapter concerning energy relation-ships, for example, we will examine the laws of thermo-dynamics.


1Barash, D. P. 1976. The male responds to apparent female adultery in the mountain

bluebird, Sialia currucoides:An evolutionary interpretation.American Naturalist

110:1097101.

http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/


6/16

The Scientific MethodThe process of science is often described in terms of the sci-entific method.Some scientists object to outlining the steps

of the scientific method as is done in Figure 1.3 becausesuch a diagram suggests a rigid methodology. Actually, sci-entists approach their work in many different ways andeven sometimes make discoveries by chance. The mostfamous case pertains to penicillin. When examining a petridish in 1928, Alexander Fleming noticed an area around amold that was free of bacteria. Upon investigating, Flemingfound that the mold produced an antibacterial substance hecalled penicillin. Penicillin was later mass produced and is

still a successfully used antibiotic in humans today. Somescientists do not test hypothesesinstead, they makeobservations and add to the known data. For example, a sci-entist might decide to find out what types of animals live onthe ocean floor.

A discussion of the scientific process is not completewithout an admission that scientists do have to accept cer-tain assumptions. They have to believe, for example, thatnature is real and understandable and knowable by observ-ing it; that nature is orderly and uniform; that measure-

ments yield knowledge of the thing measured; and thatnatural laws are not affected by time.

Science and Social ResponsibilityScience seeks only a natural cause for the origin and historyof life. Doctrines of creation that have a mythical, philosoph-ical, or theological basis are outside the realm of sciencebecause they cannot be tested by observation and/or exper-

imentation. Creationism, which states that God created allspecies as they are today, cannot be considered sciencebecause explanations based on supernatural rather than nat-ural causes involve faith rather than data.

There are many ways in which science has improvedour lives. The discovery of antibiotics and vaccines hasexpanded the human life span. Cell biology research ishelping us understand the causes of cancer. Geneticresearch has produced new strains of agricultural plantsthat have eased the burden of feeding our burgeoningworld population. Still there are other instances in whichscience has resulted in technologies that have harmed theenvironment. Technology is a process, an instrument, or astructure that is developed or constructed using scientificprinciples. Biochemical knowledge was used to developpesticides which have helped increase agricultural yields.Pesticides, as you may know, kill not only pests but alsoother types of organisms. The book Silent Spring was writ-ten to make the public aware of the harmful environmen-

tal effects of pesticide use.Too often we blame science for these developments

and think that scientists are duty bound to pursue only

those avenues of research that are consistent with a certainsystem of values. But making value judgments is not apart of science. Ethical and moral decisions must be madeby all people. The responsibility for how we use the fruitsof science, including a given technology, must reside withpeople from all walks of life, not upon scientists alone. Sci-entists should provide the public with as much informa-tion as possible when such issues as the use of atomicenergy, fetal research, and genetic engineering are beingdebated. Then they, along with other citizens, can helpmake decisions about the future role of these technologies

in our society. All men and women have a responsibility todecide how to use scientific knowledge so that it benefitsthe human species and all living things.

6 Introduction 1-6

previous data

formulation ofhypothesis

observationsand/or experimentation

new data conclusion

theory

1 2 3

observations

Figure 1.3 Flow diagram for the scientific method.On the basis of observations and previous data, a scientist

formulates a hypothesis. The hypothesis is tested by further

observations or a controlled experiment, and new data either support

or falsify the hypothesis. The return arrow indicates that a scientist

often chooses to retest the same hypothesis or to test a related

hypothesis. Conclusions from many different but related experimentsmay lead to the development of a scientific theory. For example,

studies in biology of development, anatomy, and fossil remains all

support the theory of evolution.

http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://vrl/0003l.pdfhttp://glossary.pdf/http://glossary.pdf/


7/16

1.2 The Characteristics of LifeBiological theories help us determine the characteristics oflife. Despite its diversity (see Figure 1.1), certain propertiescharacterize all living things. For example, all living thingsare organized.

Living Things Are OrganizedLiving things have levels of organization from the atomsthat constitute all matter to an ecosystem in which theylive (Fig. 1.4). Atoms join together to form molecules suchas the DNA molecules that occur only within cells. The

cell is the lowest level of biological organization to havethe characteristics of life. A nerve cell is one of the types ofcells in the body of a white-tailed deer. A tissueis a groupof similar cells that perform a particular function. Nervoustissue has millions of nerve cells that transmit signals to all

parts of the deers body. Several tissues join together toform an organ.The main organs in the nervous system ofa deer are the brain, the spinal cord, and the nerves.Organs work together to form an organ system. The brain

sends messages to the spinal cord which, in turn, sendsthem to body parts by way of the spinal nerves. An organ-ism, meaning an individual living thing, is a collection oforgan systems. A deer contains a digestive system, a circu-latory system, and several other systems in addition to anervous system. Organisms usually live within apopula-tion, which is a group of interbreeding organisms in a par-ticular locale. Several different populations interact withina community.For example, deer feed on many different

types of living plants. An ecosystem includes a communi-ty and also the physical environment. Organisms not onlyinteract with one another, they also interact with the phys-ical environment, as when a deer takes a drink of waterfrom a pond.


molecular level(DNA)cellular level

(nerve cell)

tissue level

(nervous tissue)

organ level(brain)

organ system level(nervous system)

organism level(white-tailed deer)

other levels(population, community, ecosystem)

Figure 1.4 Levels of biological organization.

http://sgch01.pdf/http://sgch01.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://vrl/0007l.pdfhttp://sgch01.pdf/http://vrl/0007l.pdfhttp://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/


8/16

8 Introduction 1-8

Living Things Acquire Materials andEnergyLiving things cannot maintain their organization nor carryon lifes other activities without an outside source of materi-als and energy. Photosynthesizers, such as trees, use carbondioxide, water, and solar energy to make their own food.Human beings and other animals, like ospreys (Fig. 1.5),acquire materials and energy when they eat food.

Food provides nutrient molecules, which are used asbuilding blocks or for energy. Energy is the capacity to dowork, and it takes work to maintain the organization of the

cell and of the organism. When nutrient molecules are usedto make their parts and products, cells carry out a sequenceof synthetic chemical reactions. Some nutrient molecules arebroken down completely to provide the necessary energy tocarry out synthetic reactions.

Most living things can convert energy into motion. Self-directed movement, as when we decide to rise from a chair,is even considered by some to be a characteristic of life.

Living Things are HomeostaticHomeostasismeans staying the same. Actually, the inter-nal environment stays relatively constant; for example, thehuman body temperature fluctuates slightly during the day.

Also, the bodys ability to maintain a normal internal tem-perature is somewhat dependent on the external tempera-turewe will die if the external temperature becomes

overly hot or cold.All human systems contribute to homeostasis. The

digestive system provides nutrient molecules; the circula-tory system transports them about the body; and the excre-tory system rids blood of metabolic wastes. The nervousand hormonal systems coordinate the activities of the oth-er systems. One of the major purposes of this text is toshow how all the systems of the human body help to main-tain homeostasis.

Living Things Respond to StimuliLiving things respond to external stimuli, often by movingtoward or away from the stimulus. Movement in humans isdependent upon their nervous and muscular systems. Otherliving things use a variety of mechanisms in order to move.Leaves of plants track the passage of the sun during the day,and when a houseplant is placed near a window, its stem

bends to face the sun.The movement of an organism, whether self-directed or

in response to a stimulus, constitutes a large part of anorganisms behavior. Behavior largely is directed towardminimizing injury, acquiring food, and reproducing.

Figure 1.5 Living things acquire materials and energy.An osprey is a large bird that preys on fishes as its source of food.

Figure 1.6 Living things reproduce.An osprey lays two to four eggs in a large nest located on the top of a

tree, a rock pinnacle, or even a telephone pole. The fledglings are

ready to leave the nest 40 to 50 days after hatching.

http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/


9/16


Living Things ReproduceLife comes only from life. The presence of genes in the form of

DNA molecules allows cells and organisms to reproducethat is, make more of themselves (Fig. 1.6). DNA contains thehereditary information that directs the structure andmetabo-lism, chemical reactions of a cell. Before reproduction occurs,genes are replicated and copies of genes are produced.

Unicellular organisms reproduce asexually simply bydividing. The new cells have the same genes and structureas the single parent. Multicellular organisms usually repro-duce sexually. Each parent, male and female, contributesroughly one-half the total number of genes to the offspring,which then does not resemble either parent exactly.

Living Things Grow and DevelopGrowth, recognized by an increase in size and often the num-ber of cells, is a part of development. In humans, develop-ment includes all the changes that take place betweenconception and death. First, the fertilized egg develops into anewborn, and then a human goes through the stages of child-

hood, adolescence, adulthood, and aging. Development alsoincludes the repair that takes place following an injury.

All organisms undergo development. Figure 1.7 illus-trates that an oak tree progresses from an acorn to a seedlingbefore it becomes an adult oak tree.

Living Things Are AdaptedAdaptations are modifications that make an organism

suited to its way of life. Consider, for example, a bird likean osprey (see Fig. 1.5), which catches and eats fish. Anosprey can fly in part because it has hollow bones toreduce its weight and flight muscles to depress and ele-vate the wings. When an osprey dives, its strong feet takethe first shock of the water and then its long and sharpclaws hold onto its slippery prey.

Adaptations come about through evolution. Evolu-tion is the process by which characteristics of species (agroup of similarly constructed organisms that successfullyinterbreed) change through time. When new variationsarise that allow certain members of the species to capturemore resources, these members tend to survive and tohave more offspring than the other unchanged members.Therefore, each successive generation will include moremembers with the new variation. In the end, most mem-bers of a species have the same adaptations to their envi-ronment.

Evolution, which has been going on since the origin of

life, explains both the unity and the diversity of life. Allorganisms share the same characteristics of life becausetheir ancestry can be traced to the first cell or cells. Organ-isms are diverse because they are adapted to differentways of life.

need confirmation of photo

Figure 1.7 Living things grow and develop.Stages in the development of an oak tree from an acorn to a seedling to an adult.

http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/


10/16

Living Things Belong to a PopulationIndividual organisms belong to a population,all the mem-bers of a species that live within a particular community.

The populations within a community interact among them-selves and with the physical environment (soil, atmosphere,etc.), thereby forming an ecosystem. All ecosystems areincluded within the biosphere,a thin layer of life that encir-cles the earth.

Although an ecosystem like a tropical rain forestchangessome trees fall and some animals diean ecosys-tem remains recognizable year after year. We say it is indynamic balance. In many cases, even the extinction ofspecies (and their replacement by new species through evo-

lution) still allows the dynamic balance of the system to bemaintained.

A major feature of the interactions between populationspertains to who eats whom. Plants produce food, and ani-mals that eat plants are food for other animals. Such asequence of organisms is called a food chain (Fig. 1.8). Bothplants and animals interact with the physical environment,as when they exchange gases with the atmosphere.

Nutrients cycle within and between ecosystems. Plantstake in inorganic nutrients, like carbon dioxide and water,and produce organic nutrients, such as carbohydrates, thatare used by themselves and various levels of animal con-sumers. When these organisms die and decay, inorganicnutrients are made available to plants once more. The bluearrows in Figure 1.8 show how chemicals cycle through thevarious populations of an ecosystem.

In contrast, the yellow arrows in Figure 1.8 show howenergy flows through an ecosystem: solar energy used byplants to produce organic food is eventually converted toheat when organisms, including plants, use organic food asan energy source. Therefore, a constant supply of solar ener-

gy is required for an ecosystem and for life to exist.

All living things share the same characteristics of

life: they are organized; take materials and energy

from the environment; are homeostatic; respond to

stimuli; reproduce; grow and develop; are adapted

to their way of life; and belong to populations.

10 Introduction 1-10

death and decomposition

Key:

energy

nutrientsheat

inorganic nutrients

heat heat

heat

heat

Figure 1.8 Ecosystem organization.Within an ecosystem, nutrients cycle (see blue arrows); plants make and use their own organic food, and this becomes food for several levels of

animal consumers, including humans. When these organisms die and decompose, the inorganic remains are used by plants as they produce

organic food. Energy flows (see yellow arrows); solar energy used by plants to produce organic food is eventually converted to heat by all

members of an ecosystem (therefore, a constant supply of solar energy is required for life to exist).

http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://vrl/0009l.pdfhttp://glossary.pdf/http://glossary.pdf/http://glossary.pdf/http://glossary.pdf/


11/16


12/16

So far, nearly 2 million species of organisms have been discov-ered and named. Two-thirds of the plant species, 90% of the

nonhuman primates, 40% of birds of prey, and 90% of the insects

live in the tropics. Many more species of organisms (perhaps as

many as 30 million) are estimated to live in the tropical rain

forests but have not yet been discovered.

Tropical forests span the planet on both sides of the equator

and cover 67% of the total land surface of the earthan area

roughly equivalent to our contiguous forty-eight states. Every

year humans destroy an area of forest equivalent to the size ofOklahoma. At this rate, these forests and the species they con-

tain will disappear completely in just a few more decades. Even

if the forest areas now legally protected survive, 5672% of all

tropical forest species would still be lost.

The loss of tropical rain forests results from an interplay of

social, economic, and political pressures. Many people already

live in the forest, and as their numbers increase, more of the land

is cleared for farming. People move to the forests because inter-

nationally financed projects build roads and open the forests upfor exploitation. Small-scale farming accounts for about 60% of

tropical deforestation, and this is followed by commercial log-

ging, cattle ranching, and mining. International demand for tim-

ber promotes destructive logging of rain forests in Southeast Asia

and South America. A market for low-grade beef encourages the

conversion of tropical rain forests to pastures for cattle. The lure

of gold draws miners to rain forests in Costa Rica and Brazil.

The destruction of tropical rain forests produces only short-

term benefits but is expected to cause long-term problems. The

forests soak up rainfall during the wet season and release it dur-

ing the dry season. Without them, a regional yearly regime of

flooding followed by drought is expected to destroy property

and reduce agricultural harvests. Worldwide, there could be

changes in climate that would affect the entire human race. On

the other hand, the preservation of tropical rain forests offers

benefits. For example, the rich diversity of plants and animals

would continue to exist for scientific and pharmacological study.

One-fourth of the medicines we currently use come from tropical

rain forests. The rosy periwinkle from Madagascar has producedtwo potent drugs for use against Hodgkin disease, leukemia,

and other blood cancers. It is hoped that many of the still-

unknown plants will provide medicines for other human ills.

Studies show that if the forests were used as a sustainable

source of nonwood products, such as nuts, fruits, and latex rub-

ber, they would generate as much or more revenue while con-

tinuing to perform their various ecological functions. And

biodiversity could still be preserved. Brazil is exploring the con-

cept of extractive reserves, in which plant and animal prod-ucts are harvested but the forest itself is not cleared. Ecologists

have also proposed forest farming systems, which mimic the

natural forest as much as possible while providing abundant

yields. But for such plans to work maximally, the human popu-

lation size and the resource consumption per person must be

stabilized.

Preserving tropical rain forests is a wise investment. Such

action promotes the survival of most of the worlds species

indeed, the human species, too.

12

Tropical Rain Forests: Can We Live Without Them?

The Human PopulationThe human population tends to modify existing ecosystemsfor its own purposes. As more and more ecosystems are con-verted to towns and cities, fewer of the natural cycles areable to function adequately to sustain an evergrowinghuman population. It is important to do all we can to pre-

serve ecosystems, because only then can we be assured thatwe will continue to exist. The recognition that the workingsof the ecosystems need to be preserved is one of the mostimportant developments of our new ecological awareness.

Presently, there is great concern about preserving theworlds tropical rain forests, as discussed in the reading onthis page. The tropical rain forests perform many servicesfor us. For example, they act like a giant sponge and absorbcarbon dioxide, a pollutant that pours into the atmosphere

from the burning of fossil fuels such as oil and coal. If therain forests continue to be depleted as they are now, anincreased amount of carbon dioxide in the atmosphere isexpected to cause an increase in the average daily tempera-ture. Problems with acid rain are also expected to increase,

since carbon dioxide combines with water to form carbonicacid, a component of acid rain.

The present biodiversity(number and size of populationsin a community) of our planet is being threatened. It has beenestimated that the number of species in the biosphere may beas high as 80 million species, but thus far fewer than 2 million

have been identified and named. Even so we may be present-ly losing from 24 to even 100 species a day due to humanactivities. The existence of the species featured in Figure 1.9 isthreatened because tropical rain forests are being reduced insize. Most biologists are alarmed over the present rate ofextinction and believe the rate may eventually rival the massextinctions that have occurred during our planets history.

The human population tends to modify existing

ecosystems and to reduce biodiversity. Becauseall living things are dependent upon the normal

functioning of the biosphere, ecosystems should

be preserved.

http://glossary.pdf/http://glossary.pdf/


13/16

1.3The Classification of Living ThingsTaxonomy is that part of biology dedicated to naming,

describing, and classifying organisms. Taxonomists use spe-cific criteria to classify species, including human beings, intocertain categories.

As we move from genus to kingdom, more and moredifferent types of species are included in each successive cat-

share very similar characteristics, but those that are in the

same kingdom have only general characteristics in common.In the same way, all species in the genus Zea look prettymuch the samethat is, like corn plantswhile species inthe plant kingdom can be quite different, as is evident whenwe compare grasses to trees.

Taxonomists give each species a scientific name in Latin.The scientific name is a binomial (bi means two; nomenmeans name). For example, the name for humans is Homosapiens, and for corn, it is Zea mays. The first word is thegenus, and the second word is a specific epithet for that

species. (Note that both words are in italic but only the genusis capitalized.) Scientific names are universally used by biol-ogists so as to avoid confusion. Common names tend tooverlap and often are in the language of a particular country.

Taxonomy makes sense out of the bewildering variety oflife on earth. Species are classified according to their pre-sumed evolutionary relationship; those placed in the samegenus are the most closely related, and those placed in sepa-rate kingdoms are the most distantly related. As more is

known about evolutionary relationships between species,taxonomy changes. Presently many biologists recognize thefive kingdoms listed in Figure 1.10. Others disagree not onlyabout the number of kingdoms but also about which speciesshould be placed in the various categories of classification.


Categories For Humans Description

Kingdom Animalia Multicellular, moves,ingests food

Phylum Chordata Dorsal supporting rodand nerve cord

Class Mammalia Hair, mammary glands

Order Primates Adapted to climb trees

Family Hominidae Adapted to walk erect

Genus Homo Large brain, tool use

Species H. sapiens

Kingdomsof Life

Representative Organisms Organization Type of NutritionRepresentative

Organisms

Monera

Protista

Fungi

Plantae

Animalia

Microscopic singlecell (sometimeschains or mats)

Complex single cell,some multicellular

Some unicellular,

most multicellularfilamentous formswith specializedcomplex cells

Multicellular formwith specializedcomplex cells

Multicellular formwith specializedcomplex cells

Absorb food(some photo-synthesize)

Absorb,photosynthesize,or ingest food

Absorb food

Photosynthesizefood

Ingest food

Bacteria includingcyanobacteria

Protozoans,algae, water molds,and slime mold

Molds, yeast,and mushrooms

Mosses, ferns,nonwoody andwoody floweringplants

Invertebrates,fishes, reptiles,amphibians, birds,and mammals

bacillispirochete Anabaena Gl oeocapsa

black bread mold yeast mushroom bracket fungus

coral earthworm blue jay squirrel

moss fern pine treenonwoodyflowering plant

paramecium euglenoid slime mold dinoflagellate

egory. Only human beings are in the genusHomo,but manydifferent types of animals are in the animal kingdom. Noticethat in the example given, species within the same genus

Figure 1.10 Classification of organisms.In this text, organisms are classified into the five kingdoms illustrated in this table.

http://sgch01.pdf/http://sgch01.pdf/http://glossary.pdf/http://sgch01.pdf/http://glossary.pdf/


14/16

Summarizing the Concepts

1.1 The Scientific ProcessWhen studying the world of living things, biologists and other scien-

tists use the scientific process. Observations along with previous data

are used to formulate a hypothesis. New observations and/or experi-ments are carried out in order to test the hypothesis. Scientists often do

controlled experiments. The control sample does not go through thestep being tested, and this acts as a safeguard against a wrong conclu-

sion.The new data may support a hypothesis or they may prove it false.

Hypotheses cannot be proven true. Several conclusions in a particulararea may allow scientists to arrive at a theorygeneralizations such as

the cell theory, gene theory, or the theory of evolution. Evolution is the

unifying theory of biology.Science is objective and uses conclusions based on data to arrive at

theories about the natural world. Any explanation based on supernat-ural beliefs cannot be considered science because such beliefs are not

tested in the usual scientific way.

Science does not answer ethical questions; we must do this forourselves. Knowledge provided by science, such as the contents of thistext, can assist us in making decisions that will be beneficial to human

beings and to other living things.

1.2 The Characteristics of LifeEvolution accounts for both the diversity and the unity of life we see

about usall organisms share the same characteristics of life:

1. Living things are organized. The levels of biologicalorganization extend from the cell to ecosystems: atoms andmolecules cells tissues organs organ systems organisms populations communities ecosystems. In an ecosystem, populations interact with oneanother and the physical environment.

2. Living things take materials and energy from theenvironment; they need an outside source of nutrients.

3. Living things are homeostatic; internally they stay just aboutthe same despite changes in the external environment.

4. Living things respond to stimuli; they react to internal andexternal events.

5. Living things reproduce; they produce offspring that resemblethemselves.

6. Living things grow and develop; during their lives they

changemost multicellular organisms undergo variousstages from fertilization to death.7. Living things are adapted; they have modifications that make

them suited to a particular way of life.8. All living things belong to a population, which can be defined

as all the members of the same species that occur in aparticular locale.

1.3 The Classification of Living ThingsLiving things are classified according to their evolutionary relation-

ships into these ever more specific categories: kingdom, phylum, class,

order, family, genus, species. Organisms in different kingdoms are onlydistantly related; organisms in the same genus are very closely related.

Studying the Concepts

1. What are the steps of the scientific process? Why cant thisprocess prove a hypothesis true? 2

2. What is a controlled experiment? Why must a scientist testone variable at a time? have a control group? 3

3. What is the ultimate goal of science? Give an example thatsupports your answer. 5

4. Why isnt creationism considered a part of science by biolo-gists? 6


The Endangered Species Act requiresthe federal government to identifyendangered and threatened species and toprotect their habitats, even to the extent ofpurchasing their habitats. Developers feelthat the act protects wildlife at the expenseof jobs for US citizens. In an effort to allowdevelopment in sensitive areas, it is nowpossible to move forward after a HabitatConservation Plan (HCP) is approved. An

HCP permits, say, new-home constructionor logging on a part of the land if wildlifehabitat is conserved on another part. Con-servation can also mean helping the gov-ernment buy habitat some place else.

The nations first HCP was approvedin 1980. It permitted housing constructionon San Bruno Mountain near San Francisco,

if 97% of the habitat for the endangeredmission blue butterfly was preserved. Thatsounds pretty good, but by this time hun-dreds of HCPs have been approved, andthe conservation requirement may haveslipped a bit. Tim Cullinan, a director ofthe National Audubon Society, recentlyfound that logging companies in the Pacif-ic Northwest are proposing the exchangeof habitat on public land for the right to

log privately owned old forests. In otherwords, nothing has been given up. Bynow, there are so many HCPs in the worksthey are being rubber-stamped by govern-ment officials with no public review at all.

Do you favor development overpreservation of habitat or vice versa? Doyou think the federal government should

be in the business of trying to preserveendangered species? Do you think thatpublic review of HCPs should be allowed,even if it slows down the approvalprocess? Is it the publics responsibility toremain vigilant or is governmental reviewof HCPs sufficient?

Questions1. What are the concerns of developers

versus environmentalists with regard to

natural areas?2. Is it short-sighted to stress the importance

of jobs over the rights of wildlife? Why orwhy not?

3. In what ethical ways can each side maketheir concerns known to the generalpublic?


Go To Student OLC


15/16


16/16


Match the terms to these definitions:a. Concept consistent with conclusions based on a

large number of experiments and observations.b. Statement that is capable of explaining present

observations and will be tested by further experimentationand observations.

c. Capacity to do work and bring about change;occurs in a variety of forms.

d. Suitability of an organism for its environmentenabling it to survive and produce offspring.

e. Maintenance of the internal environment of an

organism within narrow limits.

Understanding the Terms

adaptation 9behavior 8

biodiversity 12biology 2biosphere 10cell 7community 7conclusion 5control group 3data 5development 9ecosystem 7

energy 8evolution 9experiment 3falsify 5gene 9homeostasis 8

hypothesis 2law 5

metabolism 9organ 7organism 7organism system 7phenomenon 2population 7principle 5reproduce 9science 2scientific method 6

scientific theory 5species 9taxonomy 13technology 6tissue 7variable 3

Further Readings for Chapter 1

Balick, M. J., and Cox, P. A. 1996. Plants, people, and culture: Thescience of ethnobotany. New York: Scientific American Library.

This well-illustrated book discusses the medicinal andcultural uses of plants, and the importance of rain forestconservation.

Barnard, C., et al. 1993.Asking questions in biology. Essex: LongmanScientific & Technical. First-year life science students areintroduced to the skills of scientific observation.

Carey, S. S. 1997.A beginners guide to scientific method. 2d ed.Belmont, Calif.: Wadsworth Publishing. The basics of thescientific method are explained.

Cox, G. W. 1997. Conservation biology. Dubuque, Iowa: Wm. C.Brown Publishers. This text examines the field ofconservation, surveys basic principles of ecology andconsiders how biodiversity can be preserved.

Dobson, A. P. 1996. Conservation and biodiversity. New York:Scientific American Library. Discusses the value of

biodiversity, and describes attempts to manage endangeredspecies.

Drewes, F. 1997.How to study science. 2d ed. Dubuque, Iowa: Wm.C. Brown Publishers. Supplements any introductory sciencetext; shows students how to study and take notes and how tointerpret text figures.

Frenay, A. C. F., and Mahoney, R. M. 1997. Understanding medicalterminology. 10th ed. Dubuque, Iowa: Wm. C. BrownPublishers. A structural approach to the study of medicalterminology.

Johnson, G. B. 1996.How scientists think. Dubuque, Iowa: Wm. C.Brown Publishers. Presents the rationale behind 21 importantexperiments in genetics and molecular biology that becamethe foundation for todays research.

Kellert, S. R. 1996. The value of life: Biological diversity and humansociety. Washington D.C.: Island Press/Shearwater Books. Theimportance of biological diversity to the well-being of

humanity is explored.Marchuk, W. N. 1992.A life science lexicon. Dubuque, Iowa: Wm. C.

Brown Publishers. Helps students master life sciencesterminology.

Margulis, L., et al. 1998.Five kingdoms: An illustrated guide to thephyla of life on earth. New York: W. H. Freeman & Co.Introduces the kingdoms of organisms.

Minkoff, E. C., and Baker, P. J. 1996. Biology today: An issuesapproach. New York: The McGraw-Hill Companies, Inc. Thisintroductory text emphasizes understanding of selected

biological issues, and discusses each issues social context.Nemecek, S. August 1997. Frankly, my dear, I dont want a dam.

Scientific American 277(2):20. The article discusses how damsaffect biodiversity.

Primak, R. B. 1995.A primer of conservation biology. Sunderland,Mass.: Sinauer Associates. Addresses the loss of biologicaldiversity throughout the world, and suggests remedies.

Schmidt, M. J. January 1996. Working elephants. ScientificAmerican 274(1):82. In Asia, teams of elephants serve as analternative to destructive logging equipment.

Serafini, A. 1993. The epic history of biology. New York: PlenumPress. This is a history of biology beginning with ancientEgyptian medicine.

Using Technology

Your study of biology is supported by these available technologies:

Essential Study Partner CD-ROMEvolution & Diversity Classification

Visit the Mader web site for related ESP activities.

Exploring the Internet

The Mader Home Page provides resources and tools asyou study this chapter.

http://www.mhhe.com/biosci/genbio/mader

http://www.mhhe.com/biosci/genbio/maderhttp://www.mhhe.com/biosci/genbio/mader

enquiry into life - sylvia mader

Documents