introduction to biology (outline)

7/26/2019 Introduction to Biology (outline)

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Chapter 1 Exploring Life

Lecture Outline

Overview: Biologys Most Exciting Era

Biology is the scientific study of life. You are starting your study of biology during its most excitingera. The largest and best-equipped community of scientists in historyis beginning to solve problems that once seemed unsolvable. Biology is an ongoing inquiry about the nature of life. Biologists are moving closer to understanding: How a single cell develops into an adult animal or plant. How plants convert solar energy into the chemical energy of food. How the human mind wors. How living things interact in biological communities. How the diversity of life evolved from the first microbes. !esearch breathroughs in genetics and cell biology aretransforming medicine and agriculture. "euroscience and evolutionary biology are reshaping psychology

and sociology. #olecular biology is providing new tools for anthropology and

criminology. "ew models in ecology are helping society to evaluate

environmental issues$ such as the causes and biologicalconsequences of global warming.

%nifying themes pervade all of biology.

Concept 1.1 Biologists explore life from the microscopic to thegloal scale

&ife's basic characteristic is a high degree of order. (ach level of biological organi)ation has emergent properties. Biological organi)ation is based on a hierarchy of structural

levels$ each building on the levels below. *t the lowest level are atoms that are ordered into complexbiological molecules.

Biological molecules are organi)ed into structures calledorganelles$ the components of cells.

+ells are the fundamental unit of structure and function of livingthings.

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,ome organisms consist of a single cell others are multicellularaggregates of speciali)ed cells. hether multicellular or unicellular$ all organisms mustaccomplish the same functions: uptae and processing of nutrients$excretion of wastes$ response to environmental stimuli$ andreproduction. #ulticellular organisms exhibit three ma/or structural levels

above the cell: similar cells are grouped into tissues$ severaltissues coordinate to form organs$ and several organs form anorgan system.

0or example$ to coordinate locomotory movements$ sensoryinformation travels from sense organs to the brain$ where nervoustissues composed of billions of interconnected neurons1supportedby connective tissue1coordinate signals that travel via otherneurons to the individual muscle cells. 2rganisms belong to populations$ locali)ed groups of organisms

belonging to the same species.

3opulations of several species in the same area comprise abiological community. 3opulations interact with their physical environment to form an

ecosystem. The biosphere consists of all the environments on (arth that are

inhabited by life.

Organisms interact continuously with their environment. (ach organism interacts with its environment$ which includesother organisms as well as nonliving factors. Both organism and environment are affected by the interactionsbetween them. The dynamics of any ecosystem include two ma/or processes: thecycling of nutrients and the flow of energy from sunlight toproducers to consumers. 4n most ecosystems$ producers are plants and other

photosynthetic organisms that convert light energy to chemicalenergy.

+onsumers are organisms that feed on producers and otherconsumers.

*ll the activities of life require organisms to perform wor$ andwor requires a source of energy. The exchange of energy between an organism and its environment

often involves the transformation of energy from one form toanother.

4n all energy transformations$ some energy is lost to thesurroundings as heat.

4n contrast to chemical nutrients$ which recycle within anecosystem$ energy flows through an ecosystem$ usually enteringas light and exiting as heat.

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Cells are an organisms asic unit of structure an! function. The cell is the lowest level of structure that is capable ofperforming all the activities of life. 0or example$ the ability of cells to divide is the basis of all

reproduction and the basis of growth and repair of multicellular

organisms. %nderstanding how cells wor is a ma/or research focus ofmodern biology. *t some point$ all cells contain deoxyribonucleic acid$ or 5"*$ theheritable material that directs the cell's activities. 5"* is the substance of genes$ the units of inheritance that

transmit information from parents to offspring. (ach of us began life as a single cell stoced with 5"* inheritedfrom our parents. 5"* in human cells is organi)ed into chromosomes. (ach chromosome has one very long 5"* molecule$ with hundreds

or thousands of genes arranged along its length. The 5"* of chromosomes replicates as a cell prepares to divide. (ach of the two cellular offspring inherits a complete set of

genes. 4n each cell$ the genes along the length of 5"* molecules encodethe information for building the cell's other molecules. 5"* thus directs the development and maintenance of the entire

organism. #ost genes program the cell's production of proteins. (ach 5"* molecule is made up of two long chains arranged in a

double helix. (ach lin of a chain is one of four nucleotides$ encoding the cell'sinformation in chemical letters.

The sequence of nucleotides along each gene codes for a specificprotein with a unique shape and function. *lmost all cellular activities involve the action of one or more

proteins. 5"* provides the heritable blueprints$ but proteins are the tools

that actually build and maintain the cell. *ll forms of life employ essentially the same genetic code. Because the genetic code is universal$ it is possible to engineer

cells to produce proteins normally found only in some otherorganism. The library of genetic instructions that an organism inherits iscalled its genome. The chromosomes of each human cell contain about 6 billion

nucleotides$ including genes coding for more than 78$888 inds ofproteins$ each with a specific function.

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(very cell is enclosed by a membrane that regulates the passageof material between a cell and its surroundings. (very cell uses 5"* as its genetic material. There are two basic types of cells: proaryotic cells andeuaryotic cells.

The cells of the microorganisms called bacteria and archaea areproaryotic. *ll other forms of life have more complex euaryotic cells. (uaryotic cells are subdivided by internal membranes intovarious organelles. 4n most euaryotic cells$ the largest organelle is the nucleus$

which contains the cell's 5"* as chromosomes. The other organelles are located in the cytoplasm$ the entire

region between the nucleus and outer membrane of the cell. 3roaryotic cells are much simpler and smaller than euaryoticcells. 4n a proaryotic cell$ 5"* is not separated from the cytoplasm in

a nucleus. There are no membrane-enclosed organelles in the cytoplasm. *ll cells$ regardless of si)e$ shape$ or structural complexity$ arehighly ordered structures that carry out complicated processesnecessary for life.

Concept 1." Biological systems are much more than the sum oftheir parts

9The whole is greater than the sum of its parts. The combination of components can form a more complexorgani)ation called a system. (xamples of biological systems are cells$ organisms$ and

ecosystems. +onsider the levels of life. ith each step upward in the hierarchy of biological order$ novel

properties emerge that are not present at lower levels. These emergent properties result from the arrangements andinteractions between components as complexity increases. * cell is much more than a bag of molecules. 2ur thoughts and memories are emergent properties of a complex

networ of neurons. This theme of emergent properties accents the importance ofstructural arrangement. The emergent properties of life are not supernatural or unique tolife but simply reflect a hierarchy of structural organi)ation.

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The emergent properties of life are particularly challengingbecause of the unparalleled complexity of living systems.

The complex organi)ation of life presents a dilemma to scientistsseeing to understand biological processes. e cannot fully explain a higher level of organi)ation by breaing

it down into its component parts. *t the same time$ it is futile to try to analy)e something ascomplex as an organism or cell without taing it apart.

!eductionism$ reducing complex systems to simpler components$is a powerful strategy in biology. The Human ;enome 3ro/ect1the sequencing of the genome of

humans and many other species1is heralded as one of thegreatest scientific achievements ever.

!esearch is now moving on to investigate the function of genesand the coordination of the activity of gene products.

Biologists are beginning to complement reductionism with new

strategies for understanding the emergent properties of life1howall of the parts of biological systems are functionally integrated. The ultimate goal of systems biology is to model the dynamicbehavior of whole biological systems. *ccurate models allow biologists to predict how a change in one or

more variables will impact other components and the wholesystem.

,cientists investigating ecosystems pioneered this approach inthe 8s with elaborate models diagramming the interactions ofspecies and nonliving components in ecosystems. ,ystems biology is now becoming increasingly important in cellular

and molecular biology$ driven in part by the deluge of data from thesequencing of genomes and our increased understanding of proteinfunctions. 4n ?886$ a large research team published a networ of protein

interactions within a cell of a fruit fly. Three ey research developments have led to the increasedimportance of systems biology.1. #igh$throughput technology.,ystems biology depends on

methods that can analy)e biological materials very quicly andproduce enormous amounts of data. *n example is the automatic5"*-sequencing machines used by the Human ;enome 3ro/ect.

2. Bioinformatics.The huge databases from high-throughputmethods require computing power$ software$ and mathematicalmodels to process and integrate information.

3. %nter!isciplinary research teams.,ystems biology teams mayinclude engineers$ medical scientists$ physicists$ chemists$mathematicians$ and computer scientists as well as biologists.

&egulatory mechanisms ensure a !ynamic alance in living systems.

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+hemical processes within cells are accelerated$ or cataly)ed$ byspeciali)ed protein molecules$ called en)ymes. (ach type of en)yme cataly)es a specific chemical reaction. 4n many cases$ reactions are lined into chemical pathways$ each

step with its own en)yme.

How does a cell coordinate its various chemical pathways@ #any biological processes are self-regulating: the output or

product of a process regulates that very process. 4n negative feedbac$ or feedbac inhibition$ accumulation of an

end product of a process slows or stops that process. Though less common$ some biological processes are regulated bypositive feedbac$ in which an end product speeds up its ownproduction. 0eedbac is common to life at all levels$ from the molecular level

to the biosphere. ,uch regulation is an example of the integration that maes living

systems much greater than the sum of their parts.

Concept 1.' Biologists explore life across its great !iversity ofspecies

Biology can be viewed as having two dimensions: a 9verticaldimension covering the si)e scale from atoms to the biosphere and a9hori)ontal dimension that stretches across the diversity of life. The latter includes not only present-day organisms$ but also those

that have existed throughout life's history. Living things show !iversity an! unity.

&ife is enormously diverse. Biologists have identified and named about


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"ew methods$ including comparisons of 5"* among organisms$have led to a reassessment of the number and boundaries of theingdoms. Carious classification schemes now include six$ eight$ or evendo)ens of ingdoms.

+oming from this debate has been the recognition that there arethree even higher levels of classifications$ the domains. The three domains are Bacteria$ *rchaea$ and (uarya. The first two domains$ domain Bacteria and domain *rchaea$

consist of proaryotes. *ll the euaryotes are now grouped into various ingdoms of thedomain (uarya. The recent taxonomic trend has been to split the single-celled

euaryotes and their close relatives into several ingdoms. 5omain (uarya also includes the three ingdoms of multicellular

euaryotes: the ingdoms 3lantae$ 0ungi$ and *nimalia.

These ingdoms are distinguished partly by their modes ofnutrition. #ost plants produce their own sugars and food by photosynthesis. #ost fungi are decomposers that absorb nutrients by breaing

down dead organisms and organic wastes. *nimals obtain food by ingesting other organisms. %nderlying the diversity of life is a striing unity$ especially atthe lower levels of organi)ation. The universal genetic language of 5"* unites proaryotes and

euaryotes. *mong euaryotes$ unity is evident in many details of cell

structure. *bove the cellular level$ organisms are variously adapted to their

ways of life. How do we account for life's dual nature of unity and diversity@ The process of evolution explains both the similarities and

differences among living things.

Concept 1.( Evolution accounts for lifes unity an! !iversity The history of life is a saga of a changing (arth billions of yearsold$ inhabited by a changing cast of living forms. +harles 5arwin brought evolution into focus in


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This term captured the duality of life's unity and diversity: unityin the inship among species that descended from commonancestors and diversity in the modifications that evolved asspecies branched from their common ancestors.

5arwin's second point was his mechanism for descent withmodification: natural selection. 5arwin inferred natural selection by connecting two observations: 2bservation


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The word science is derived from a &atin verb meaning 9to now. *t the heart of science is inquiry$ people asing questions aboutnature and focusing on specific questions that can be answered. The process of science blends two types of exploration: discoveryscience and hypothesis-based science.

5iscovery science is mostly about discovering nature. Hypothesis-based science is mostly about explaining nature. #ost scientific inquiry combines the two approaches. 5iscovery science describes natural structures and processes asaccurately as possible through careful observation and analysis ofdata. 5iscovery science built our understanding of cell structure and is

expanding our databases of genomes of diverse species. 2bservation is the use of the senses to gather information$ whichis recorded as data.

5ata can be qualitative or quantitative. Fuantitative data are numerical measurements. Fualitative data may be in the form of recorded descriptions. Eane ;oodall has spent decades recording her observations of

chimpan)ee behavior during field research in ;ambia. ,he has also collected volumes of quantitative data over thattime. 5iscovery science can lead to important conclusions based oninductive reasoning. Through induction$ we derive generali)ations based on a large

number of specific observations.

4n science$ inquiry frequently involves the proposing and testingof hypotheses. * hypothesis is a tentative answer to a well-framed question. 4t is usually an educated postulate$ based on past experience andthe available data of discovery science. * scientific hypothesis maes predictions that can be tested byrecording additional observations or by designing experiments. * type of logic called deduction is built into hypothesis-basedscience. 4n deductive reasoning$ reasoning flows from the general to the

specific. 0rom general premises$ we extrapolate to a specific result thatwe should expect if the premises are true.

4n hypothesis-based science$ deduction usually taes the form ofpredictions about what we should expect if a particular hypothesisis correct. e test the hypothesis by performing the experiment to see

whether or not the results are as predicted.Lecture Outline for Campbell/Reece Biology, 7thEdition, Pearson Education, Inc. 1'


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5eductive logic taes the form of 94f . . . then logic. ,cientific hypotheses must be testable. There must be some way to chec the validity of the idea. ,cientific hypotheses must be falsifiable. There must be some observation or experiment that could reveal

if a hypothesis is actually not true. The ideal in hypothesis-based science is to frame two or morealternative hypotheses and design experiments to falsify them. "o amount of experimental testing can prove a hypothesis. * hypothesis gains support by surviving various tests that couldfalsify it$ while testing falsifies alternative hypotheses. 0acts$ in the form of verifiable observations and repeatableexperimental results$ are the prerequisites of science.

+e can explore the scientific metho!.

There is an ideali)ed process of inquiry called the scientificmethod. Cery few scientific inquiries adhere rigidly to the sequence of

steps prescribed by the textboo scientific method. 5iscovery science has contributed a great deal to our

understanding of nature without most of the steps of the so-called scientific method.

e will consider a case study of scientific research. This case begins with a set of observations and generali)ationsfrom discovery science. #any poisonous animals have warning coloration that signalsdanger to potential predators. 4mposter species mimic poisonous species$ although they are

harmless. *n example is the bee fly$ a nonstinging insect that mimics a

honeybee. hat is the function of such mimicry@ hat advantage does it

give the mimic@ 4n ?$ Henry Bates proposed that mimics benefit whenpredators mistae them for harmful species. This deception may lower the mimic's ris of predation. 4n ?88


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"atural selection may have favored an instinctive recognition andavoidance of the warning coloration of the coral snae. The nonpoisonous scarlet ing snae mimics the ringed colorationof the coral snae. Both ing snaes and coral snae live in the +arolinas$ but the ing

snae's range also extends into areas without coral snaes. The distribution of these two species allowed the 3fennigs andHarcombe to test a ey prediction of the mimicry hypothesis. #imicry should protect the ing snae from predators$ but only in

regions where coral snaes live. 3redators in noncoral snae areas should attac ing snaes

more frequently than predators that live in areas where coralsnaes are present.

To test the mimicry hypothesis$ Harcombe made hundreds ofartificial snaes. The experimental group had the red$ blac$ and yellow ring

pattern of ing snaes. The control group had plain$ brown coloring. (qual numbers of both types were placed at field sites$ includingareas where coral snaes are absent. *fter four wees$ the scientists retrieved the fae snaes andcounted bite or claw mars. 0oxes$ coyotes$ raccoons$ and blac bears attaced snae models. The data fit the predictions of the mimicry hypothesis. The ringed snaes were attaced by predators less frequently

than the brown snaes only within the geographic range of thecoral snaes.

The snae mimicry experiment provides an example of howscientists design experiments to test the effect of one variable bycanceling out the effects of unwanted variables. The design is called a controlled experiment. *n experimental group Iartificial ing snaesJ is compared with a

control group Iartificial brown snaesJ. The experimental and control groups differ only in the one factor

the experiment is designed to test1the effect of the snae'scoloration on the behavior of predators.

The brown artificial snaes allowed the scientists to rule out suchvariables as predator density and temperature as possibledeterminants of number of predator attacs.

,cientists do not control the experimental environment byeeping all variables constant. !esearchers usually 9control unwanted variables$ not by

eliminating them but by canceling their effects using controlgroups.

Lets loo, at the nature of science.Lecture Outline for Campbell/Reece Biology, 7thEdition, Pearson Education, Inc. 111


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There are limitations to the inds of questions that science canaddress. These limits are set by science's requirements that hypothesesare testable and falsifiable and that observations and experimentalresults be repeatable.

The limitations of science are set by its naturalism. ,cience sees natural causes for natural phenomena. ,cience cannot support or falsify supernatural explanations$

which are outside the bounds of science. (veryday use of the term theory implies an untested speculation. The term theory has a very different meaning in science. * scientific theory is much broader in scope than a hypothesis. This is a hypothesis: 9#imicing poisonous snaes is an adaptation

that protects nonpoisonous snaes from predators. This is a theory: 9(volutionary adaptations evolve by natural

selection. * theory is general enough to generate many new$ specifichypotheses that can be tested. +ompared to any one hypothesis$ a theory is generally supportedby a much more massive body of evidence. The theories that become widely adopted in science Isuch as thetheory of adaptation by natural selectionJ explain many observationsand are supported by a great deal of evidence. 4n spite of the body of evidence supporting a widely acceptedtheory$ scientists may have to modify or re/ect theories when newevidence is found.

*s an example$ the five-ingdom theory of biological diversityeroded as new molecular methods made it possible to test someof the hypotheses about the relationships between livingorganisms.

,cientists may construct models in the form of diagrams$ graphs$computer programs$ or mathematical equations. #odels may range from lifelie representations to symbolic

schematics. ,cience is an intensely social activity. #ost scientists wor in teams$ which often include graduate and

undergraduate students.

Both cooperation and competition characteri)e scientific culture. ,cientists attempt to confirm each other's observations and may

repeat experiments. They share information through publications$ seminars$ meetings$

and personal communication. ,cientists may be very competitive when converging on the same

research question.

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ith advances in technology come difficult choices$ informed asmuch by politics$ economics$ and cultural values as by science. ,cientists should educate politicians$ bureaucrats$ corporateleaders$ and voters about how science wors and about the potentialbenefits and ha)ards of specific technologies.

Concept 1. / set of themes connects the concepts of iology 4n some ways$ biology is the most demanding of all sciences$partly because living systems are so complex and partly becausebiology is a multidisciplinary science that requires nowledge ofchemistry$ physics$ and mathematics. Biology is also the science most connected to the humanities andsocial sciences.

Lecture Outline for Campbell/Reece Biology, 7thEdition, Pearson Education, Inc. 11#

introduction to biology (outline)

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