> What are some of the branches of biology?

> What are seven characteristics that allliving things share?

biologycellhomeostasismetabolism

reproductionheredityevolution

All living things on Earth aretied together by commontraits and rely on one anotherfor their common survival.

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7_e giant sequoia shown in Figure 8 is very different from the manszanding below it. But both organisms have much in common.'-mdying living organisms is what the science of biology is all about.

The s·~vj @f ll,"fe.ology is the study of life. Life is extremely diverse. It would be

_possible for one person to become an expert in all aspects of-=-:ology,so scientists specialize. There are many branches of biology.}- Biology includes biochemistry, ecology, cell biology, genetics, evolutionaryC"aory, microbiology, botany, zoology, and physiology. Biochemistry is the~~ dy of the chemistry of life. Ecology is the study of how organismsb-eract with each other and with their environment. The study of=e- on the cellular level is called cell biology. Genetics is the study:: how organisms pass traits to their offspring. Evolutionary theory=- the study of changes in types of organisms over time. The study of.:::<icroscopic organisms is called microbiology. The study of plants is~ ed botany. Zoology is the study of animals. Physiology is the study:: me human body. As you read, you will learn about each of these::clds. You will also have the opportunity to practice techniques thatzre used in careers in each of these fields.

biology the scientific study of living organismsand their interactions with the environment

Figure 8 Both the man and the sequoia treethat he is standing on are living organisms.

Which branches of biology would studyboth humans and trees?

SECTION 4 What Is Biology? 17

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r@perties L'"feAll living organisms share certain properties. ~ The seven propertiesof life are cellular organization, homeostasis, metabolism, responsiveness,reproduction, heredity, and growth. Life is characterized by the presenceof all seven properties at some stage in an organism's life.

Cellular Organi:!:ati@1i'iI A cell is the smallest unit capable of all lifefunctions. A cell is a highly organized, tiny structure that is enclosedin a thin covering called a membrane. The basic structure of cells isthe same in all organisms.

anging Around for ScienceSometimes, field biologists hang around ininteresting places. Scientists who study thebiology of cave-dwelling organisms are calledspeleologists. This scientist is hanging over a'cave called the Well of the Birds. This sinkholeis more than 200 meters deep and growing.

Life Under Water This marine biologist has togo underwaterto study manatees in their habitat.Manateesare an endangeredspecies. Scientistshope that by learning about manatees,we maybeable to prevent the extinction of this species.

Homeostasis All living organisms must maintain a stableinternal environment in order to function properly. Themaintenance of stable internal conditions in spite of changesin the external environment is called homeostasis.

Metali»@lism Living things carry out many chemical reac-tions in order to obtain energy. Metabolism is the sum of allof the chemical reactions carried out in an organism. Almostell of the energy used by living things originally comes fromsunlight. Plants, algae, and some bacteria capture this energyand use it to make molecules. These molecules serve as thesource of energy, or food, for other organisms.

RespOi'!l!!hf$U'ieSS In addition to maintaining a stableinternal environment, living organisms also respond totheir external environment. Plants bend toward sunlight.Birds fluff their feathers to insulate their bodies during cold weather.Students, shown in Figure 9, also respond to their environment.

Reprcductnon Most living things can reproduce. Reproduction isme process by which organisms make more of their own kind fromone generation to the next. Because no organism lives forever, repro-

uction is an essential part of life.

Heredity When an organism reproduces, it passes on its own traitsa its offspring in a process known as heredity. Heredity is the reason

that children tend to look like their parents. Inherited characteristicschange over generations. This process is called evolution.

Growth All living organisms grow. Some one-celled organismsonly grow briefly, during the time that they are reproducing. Otherliving things, like the giant sequoia, grow for thousands of years andreach an enormous size. As organisms grow, many change. This_rocess is called development. Frogs begin as eggs, develop intotadpoles, and eventually develop into frogs. Development differsHorn evolution because development refers to change in a singlefudividual during that individual's life.

,< ;) Reading Ci1ercf{ How is heredity related to evolution?

ReviewKEYmEA~1. Explain what biology is.2. Describe nine fields that are part

of the science of biology.3. Name the basic unit of life.4. Discuss the seven properties all

living organisms share.5. Define homeostasis.

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C ITiCAt HiNKDNG6. Recognizing Verifiable Facts If you

find an object that seems alive,how might you determine if theobject is indeed an organism?

7. Elaborating Give an exampleof one way that you areinterdependent on another type oforganism.

S. Analyzing Information Relate fiveof the characteristics of life to anorganism familiar to xou .

Figure 9 These students are re$:pondingto the rain by using raincoats. ~~n youthink of a way that you have respoq~ed toyour environment today? .

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cell in biology,thesmallestunitthatcanperformall lifeprocesses

homeostasis themaintenanceofaconstantinternalstateina changingenvironment

metabolism thesumof all chemicalproc-essesthatoccurin anorganism

reproduction theprocessof producingoffspring

heredity thepassingofgenetictraitsfrom, parentto offspring

evolution theprocessof changeby whichnewspeciesdevelopfrompreexistingspeciesovertime

ALTERNATIVE ASSESSMENTi 9. Interview a Biologist Choose; a field of biology that interests

you. Locate a biologist workingin that field, and conduct aninterview by phone or e-mall,Ask the biologist how he or shebecame interested in his or herfield and what the scientist'swork is like. Report yourfindings to the class.

SECTION 4 What Is Biology? 19 {/

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