Preview Campbell Biology Concepts Connections by Reece, Jane BTaylor, Martha RSimon, Eric JDickey, Jean L (2020)Preview Campbell Biology Concepts Connections by Reece, Jane BTaylor, Martha RSimon, Eric JDickey, Jean L (2020) Preview Campbell Biology Concepts Connections by Reece, Jane BTaylor, Martha RSimon, Eric JDickey, Jean L (2020)
GLOBAL EDITION $BNQCFMM#JPMPHZ Concepts & Connections EIGHTH EDITION +BOF#3FFDFt.BSUIB35BZMPSt&SJD+4JNPOt+FBO-%JDLFZt,FMMZ)PHBO CAMPBELL BIOLOGY CONCEPTS & CONNECTIONS EIGHTH EDITION GLOBAL EDITION J A N E B R E E C E Berkeley, California E R I C J S I M O N New England College M A R T H A R T A Y L O R Ithaca, New York J E A N L D I C K E Y Clemson University K E L L Y H O G A N University of North Carolina, Chapel Hill Boston Columbus Indianapolis New York San Francisco Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montréal Toronto Delhi Mexico City São Paulo Sydney Hong Kong Seoul Singagore Taipei Tokyo Editor-in-Chief: Beth Wilbur Interior Designer: Hespenheide Design Executive Director of Development: Deborah Gale Cover Image: Satit/Shutterstock Acquisitions Editor: Alison Rodal Executive Editorial Manager: Ginnie Simione Jutson Cover Designer: Lumina Datamatics Ltd Illustrations: Precision Graphics Credits and acknowledgments for materials borrowed from other sources and reproduced, with permission, in this textbook appear on the appropriate page within the text or on p 844 Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England Editorial Project Manager: Debbie Hardin Development Artists: Kelly Murphy; Andrew Recher, Precision Graphics Development Editors: Debbie Hardin, Susan Teahan Senior Photo Editor: Donna Kalal Visit us on the World Wide Web at: www.pearsonglobaleditions.com Editorial Assistant: Libby Reiser Photo Researcher: Kristin Piljay © Pearson Education Limited 2016 Senior Supplements Project Editor: Susan Berge Photo Permissions Management: Bill Smith Group Supplements Production Project Manager: Jane Brundage Director of Editorial Content MasteringBiology®: Tania Mlawer Manager, Text Permissions: Tim Nicholls Development Editor, MasteringBiology®: Juliana Tringali Project Manager, Text Permissions: Alison Bruckner Text Permissions Specialist: James Toftness, Creative Compliance, LLC Director of Production: Erin Gregg Managing Editor: Michael Early Production Project Manager: Lori Newman Acquisitions Editor, Global Edition: Shona Mullen Project Editor, Global Edition: Amrita Naskar Manager, Media Production, Global Edition: Vikram Kumar Senior Manufacturing Controller, Production, Global Edition: Trudy Kimber Design Manager: Marilyn Perry Senior Mastering® Media Producer: Katie Foley Associate Mastering® Media Producer: Taylor Merck Editorial Media Producer: Daniel Ross Senior Manager Web Development: Steve Wright Web Development Lead: Dario Wong Vice President of Marketing: Christy Lesko Executive Marketing Manager: Lauren Harp Senior Marketing Manager: Amee Mosley Manufacturing Buyer: Jeffrey Sargent and Associated Companies throughout the world The rights of Jane B Reece, Martha R Taylor, Eric J Simon, Jean L Dickey, and Kelly Hogan to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988 Authorized adaptation from the United States edition, entitled Campbell Biology: Concepts & Connections, 8e, ISBN 978-0-321-88532-6, by Jane B Reece, Martha R Taylor, Eric J Simon, Jean L Dickey, and Kelly Hogan , published by Pearson Education © 2015 All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a license permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London EC 1N 8TS All trademarks used herein are the property of their respective owners The use of any trademark in this text does not vest in the author or publisher any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of this book by such owners Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or in part, without prior written permission from the publisher Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed in initial caps or all caps ® ® MasteringBiology and BioFlix are registered trademarks, in the U.S and/or other countries, of Pearson Education, Inc or its affiliates ISBN 10: 1-292-05780-7 ISBN 13: 978-1-292-05780-4 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library 10 Typeset by S4Carlisle Publishing Services, Inc Printed and bound by Courier Kendallville in the United States of America About the Authors Jane B Reece has worked in biology publishing since 1978, when she joined the editorial staff of Benjamin Cummings Her education includes an A.B in biology from Harvard University, an M.S in microbiology from Rutgers University, and a Ph.D in bacteriology from the University of California, Berkeley At UC Berkeley, and later as a postdoctoral fellow in genetics at Stanford University, her research focused on genetic recombination in bacteria Dr Reece taught biology at Middlesex County College (New Jersey) and Queensborough Community College (New York) During her 12 years as an editor at Benjamin Cummings, she played a major role in a number of successful textbooks She is coauthor of Campbell Biology, Tenth Edition, Campbell Biology in Focus, Campbell Essential Biology, and Campbell Essential Biology with Physiology, Fourth Edition Martha R Taylor has been teaching biology for more than 35 years She earned her B.A in biology from Gettysburg College and her M.S and Ph.D in science education from Cornell University At Cornell, she has served as assistant director of the Office of Instructional Support and has taught introductory biology for both majors and nonmajors Most recently, she was a lecturer in the Learning Strategies Center, teaching supplemental biology courses Her experience working with students in classrooms, in laboratories, and with tutorials has increased her commitment to helping students create their own knowledge of and appreciation for biology She has been the author of the Student Study Guide for all ten editions of Campbell Biology Eric J Simon is a professor in the Department of Biology and Health Science at New England College (Henniker, New Hampshire) He teaches introductory biology to science majors and nonscience majors, as well as upper-level courses in tropical marine biology and careers in science Dr Simon received a B.A in biology and computer science and an M.A in biology from Wesleyan University, and a Ph.D in biochemistry from Harvard University His research focuses on innovative ways to use technology to improve teaching and learning in the science classroom, particularly for nonscience majors Dr Simon is the lead author of the introductory nonmajors biology textbooks Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition, and the author of the introductory biology textbook Biology: The Core Jean L Dickey is Professor Emerita of Biological Sciences at Clemson University (Clemson, South Carolina) After receiving her B.S in biology from Kent State University, she went on to earn a Ph.D in ecology and evolution from Purdue University In 1984, Dr Dickey joined the faculty at Clemson, where she devoted her career to teaching biology to nonscience majors in a variety of courses In addition to creating content-based instructional materials, she developed many activities to engage lecture and laboratory students in discussion, critical thinking, and writing, and implemented an investigative laboratory curriculum in general biology Dr Dickey is author of Laboratory Investigations for Biology, Second Edition, and coauthor of Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition Kelly Hogan is a faculty member in the Department of Biology at the University of North Carolina at Chapel Hill, teaching introductory biology and introductory genetics to science majors Dr Hogan teaches hundreds of students at a time, using active-learning methods that incorporate technology such as cell phones as clickers, online homework, and peer evaluation tools Dr Hogan received her B.S in biology at the College of New Jersey and her Ph.D in pathology at the University of North Carolina, Chapel Hill Her research interests relate to how large classes can be more inclusive through evidence-based teaching methods and technology She provides faculty development to other instructors through peer-coaching, workshops, and mentoring Dr Hogan is the author of Stem Cells and Cloning, Second Edition, and is lead moderator of the Instructor Exchange, a site within MasteringBiology® for instructors to exchange classroom materials and ideas Neil A Campbell (1946–2004) combined the inquiring nature of a research scientist with the soul of a caring teacher Over his 30 years of teaching introductory biology to both science majors and nonscience majors, many thousands of students had the opportunity to learn from him and be stimulated by his enthusiasm for the study of life While he is greatly missed by his many friends in the biology community, his coauthors remain inspired by his visionary dedication to education and are committed to searching for ever better ways to engage students in the wonders of biology About the Authors Make important connections between biological concepts and your life CHAPTER To the Student: dent: How to use this book and MasteringBio MasteringBiology® ology® 12 ? NEW! Each chapterr opens with a high-interest question to o spark your interest in in the topic Questions nss are revisited later in n the chapter, in either e er a Scientific Thinking g or Evolution Connection io on module DNA Technology and Genomics papaya trees on span, thousands of er of darkness, down under the cov h few would c GMO crops Althoug concerned abo should we in fact be to foster consid question continues Os in our die In addition to GM s: Gene cloning in many other way A profiling dustrial products, DN s produce v ence, new technologie n d to inv NA can even be use and DN of thes r, we’ll discuss each pter, chaapter used, how the specific techniques es thaat are r legal, and ethical issu C They are loaded with vitamin below, are sweet and y in tropical climates in the photograph aya) that grows onl pap rica apaya fruit, shown (Ca t plan g treelike win gro p cro idly ort rap a exp borne on le and a valuable decades ago A is both a dietary stap doomed just a few In Hawaii, papaya aya industry seemed out the islands today, Hawaii’s pap had spread through V) (PR s viru t Although thriving spo ion But scientists from ed the papaya ring papaya plant populat the deadly pathogen call e icat erad ely , genetically engised to complet ustry by creating new fi ed and appeared poiHaw m difi ag in vibrant—and able to rescue the ind ly mo allly ticcal y is once aga ustr g neeti ge ind a ty of a aii were ab Are gen a ay aya ersiity a ivers pap Uniiv U the , y the Un aay, day Tod T aayaa To a ay of pap afee?? organisms (GMOs) R -resistant strains ed difi rganism s saf i org mo a aineered PRV ally etic recovery of the Haw aayaass are gen a ay a aii’s pap ces surrounding the a ority of Haw stan um circ the vast maj the ut out aabo r consumption in the a py ab f fo for hap ed is ved ne rov pro y ryo app a ap eve are s as not a ay r a aya nHowever, f ty etically modified pap a e raised safe some critics hav stryyy Although gen ustr ndu a a iind ay a aya ian pap ts and vegetables), r a three-year n other GMO frui three occasions ove many On are t nt (as men me es a Stat iron n env ted ited Uni U Un f r the fo a them and for eat fforr the people who cerns—fo P 30 30 23 230 OF S4CARLISLE DESIGN SERVICES d tion / NJ / CHET 230 Au: Reece Pg No C/M/Y/K Short / Normal 8/11/13 11:15 AM es Publishing Servic ◃ ABC News Videos and Current Events articles from The New York Times connect what you learn in biology class to fascinating stories in the news iv ◃ Big Ideas help you connect the Gene Cloning (12.1–12.5) ry A variety of laborato used to techniques can be DNA copy and combine molecules ove overarching concepts that are exp explored in the chapter ▹ Genetically Modified Organisms ▿ Connection modules in every chapter (12.6–12.10) ts, Transgenic cells, plan d in and animals are use icine agriculture and med relate biology to your life and the world outside the classroom CONNECTION ▹ DNA Profiling 16.5 Biofilms are complex associations of microbes ▹ In many natural environments, prokaryotes attach t surfaces in highly organized colonies called to CONNECTION b biofilms A biofilm may consist of one or several s species of prokaryotes, and it may include protists a fungi as well Biofilms can form on almost any an and support, including rocks, soil, organic material (including living tissue), metal, and plastic You have a biofilm on your teeth—dental plaque is a biofilm that can cause tooth decay Biofilms can even form without a solid foundation, for example, on the surface of stagnant water Biofilm formation begins when prokaryotes secrete signaling molecules that attract nearby cells into a cluster Once the cluster becomes sufficiently large, the cells produce a gooey coating that glues them to the support and to each other, making the biofilm extremely difficult to dislodge For example, if you don’t scrub your shower, you could find a biofilm growing around the drain—running water alone is not strong enough to wash it away As the biofilm gets larger and more complex, it becomes a “city” of microbes Communicating by chemical signals, members of the community coordinate the division of labor, defense against invaders, and other activities Channels in the biofilm allow nutrients to reach cells in the interior and allow wastes to leave, and a variety of environments develop within it Biofilms are common among bacteria that cause disease in humans For instance, ear infections and urinary tract infections are often the result of biofilm-forming bacteria Cystic fibrosis patients are vulnerable to pneumonia caused by bacteria that form biofilms in their lungs Biofilms of harmful Genomics (12.17–12.21) e DNA The study of complet about sets helps us learn evolutionary history bacteria can also form on implanted medical devices such as catheters, replacement joints, or pacemakers The complexity of biofilms makes these infections especially difficult to defeat Antibiotics may not be able to penetrate beyond the outer layer of cells, leaving much of the community intact For example, some biofilm bacteria produce an enzyme that breaks down penicillin faster than it can diffuse inward Biofilms that form in the environment can be difficult to eradicate, too A variety of industries spend billions of dollars every year trying to get rid of biofilms that clog and corrode pipes, gum up filters and drains, and coat the hulls of ships (Figure 16.5) Biofilms in water distribution pipes may survive chlorination, the most common method of ensuring that drinking water does not contain any harmful microorganisms For example, biofilms of Vibrio cholera, the bacterium that causes cholera, found in water ▲ Figure 16.5 A biofilm fouling the insides of a pipe pipes were capable of withstanding levels of chlorine 10 to 20 times higher than the concentrations routinely used to chlorinate drinking water ? Why are biofilms difficult to eradicate? biofilm stick to each other; the outer layer of cells may prevent antimicrobial substances from penetrating into the interior of the biofilm (12.11–12.16) be used Genetic markers can ch a DNA to definitively mat al sample to an individu ● The biofilm sticks to the surface it resides on, and the cells that make up the 231 C/M/Y/K 10.19 8/11/13 11:15 AM Emerging viruses threaten human health Emerging viruses are ones that seem to burst on to Em E the scene, becoming apparent to the medical th ccommunity quite suddenly There aree many familiar examples, such as the m 2009 H1N1 influenza virus (discussed 220 d iin the h chapter introduction) Another example is HIV (human immunodeficiency virus), the virus that causes AIDS (acquired immunodeficiency syndrome) HIV appeared in New York and California in the early 1980s, seemingly out of nowhere Yet another example is the deadly Ebola virus, recognized initially in 1976 in central Africa; it is one of several emerging viruses that causee hemorrhagic fever, an often fatal syndrome charharacterized by fever, vomiting, massive bleeding, g, and circulatory system collapse A number of other er dangerous newly recognized viruses cause encephalitis, itis, inflammation of the brain Onee example is the Why are viral West Nile virus, which appeared in North America in 1999 and has since diseases such a spread to all 48 contiguous U.S states constant threat? West Nile virus is spread primarily by mosquitoes, which carry the virus in blood sucked from one victim and can transfer it to another victim West Nile virus cases surged in 2012, especially in Texas Severe acute respiratory syndrome (SARS) first appeared in China in 2002 Within eight months, about 8,000 people were infected, and 10% died Researchers quickly id ifi d h i f i i l k EVOLUTION CONNECTION EVOLUTION CONNECTION OF S4CARLISLE DESIGN SERVICES Colorized TEM 180,000 aii were hacked the big island of Haw test against presumably as a pro inal behavior, condone such crim O crops? This out the safety of GM disagreement and ate deb able der s affect our lives et, DNA technologie e medical and ing is used to produc of forensic scihas changed the field logical research, valuable data for bio ns In this g e historical questio vestigat ll also consider the W We’’ll ions We ation licaat plic aapp se ap social, d,, and some of the lied plie aapp ey are ap nologies tech new the by raised BIG IDEAS ▼ Figure 10.19 A Hong Kong health-care worker prepares to cull a chicken to help prevent the spread of the avian flu virus (shown in the inset) ◃ Evolution Connection modules present concrete examples of the evidence for evolution within each chapter, providing you with a coherent theme for the study of life To the Student: dent: How to use this book and MasteringBiology MasteringBiology® ● The ER produces a huge variety of molecules, including phospholipids for cell memb 4.9 The Golgi apparatus modifies, sort s, and Central concepts summarize the key topic of each module, helping you ou stay focused as you study Checkpoint questions at the end nd of each module help p you stay on track NEW and revised art provides clear visuals to help you understand key topics Selected figures include numbered steps that are keyed to explanations in the text ships cell products functions as a depot, dispatching its products in vesicles that bud off and travel to other sites How might ER products be processed during their transit through the Golgi? Various Golgi enzym es modify the carbohydrate portions of the glycoproteins made in the ER, removing some sugars and substituting others Mole cular identification tags, such as phosphate groups, may be added that help the Golgi sort molecules into different batches for different destinations Finished secretory products, packaged in transport vesicles, move to the plasma membrane for export from the cell Alternatively, finished products may become part of the plasma membrane itself or part of anoth er organelle, such as a lysosome, which we discuss next ? What is the relationship of the Golgi apparatus to the ER in a protein-secreting cell? ● The Golgi receives transport vesicle s budded from the ER that contain proteins synthesized by bound riboso mes The Golgi finishes processing the proteins and dispatches transport vesicles to the plasma membrane, where the proteins are secreted Stay focused onn the key concepts ts After leaving the ER, many transport vesicles travel to the Golgi apparatus Using a light micro scope and a staining technique he developed, Italian scien tist Camillo Golgi discovered this membranous organelle in 1898 The electron microscope confirmed his discovery more than 50 years later, revealing a stack of flattened sacs, looki ng much like a pile of pita bread A cell may contain many, even hundreds, of these stacks The number of Golgi stacks corre lates with how active the cell is in secreting proteins—a multi step process that, as you have just seen, is initiated in the rough ER The Golgi apparatus serves as a mole cular warehouse and processing station for products manu factured by the ER You can follow these activities in Figure 4.9 Note that the flattened Golgi sacs are not connected, as are ER sacs ➊ One side of a Golgi stack serves as a receiv ing dock for transport vesicles produced by the ER ➋ A vesic le fuses with a Golgi sac, adding its membrane and contents to the “receiving” side ➌ Products of the ER are modi fied as a Golgi sac progresses through the stack ➍ The “ship ping” side of the Golgi “Receiving” side of Golgi apparatus Transport vesicle from the ER ➊ ➋ × ,000 ➌ d, rize Colo Golgi apparatus TEM 145 ➍ Transport vesicle from the Golgi “Shipping” side of Golgi apparatus ▲ Figure 4.9 The Golgi apparatus receiv ing, processing, and shipping products The Endomembrane System 61 ◃ Connecting the Concepts activities link one biological concept to another vi 12.9 Genetically modified organisms raise health concerns A soon as scientists realized the power As of DNA techtheir new genes to related species in nology, they began to worry about poten n nearby wild areas, disSCIENTIFIC tial dangers turbing the composition of the natura Early concerns focused on the possib E l ecosystem Critics of THINKING ility GMO crops can point to several studie that t recombinant DNA technology might s that Are genetically indeed show unintended gene transf ccr create new pathogens To guard against er from enmodified gineered crops to nearby wild relativ rogue microbes, scientists developed es But GMO a set of organism s safe? advocates counter that no lasting or guidelines including strict laboratory detrimental safety and effects from such transfers have been containment procedures, the genetic demon crippling of transgenic strated, and that some GMOs (such organisms to ensure that they canno as bacteria engineered to t survive outside the labbreak down oil spills) can actively help oratory, and a prohibition on certain the environment dangerous experiments Today, most public concern centers on Labeling Although the majority of severa GMOs used for food l staple crops grown in the United States—including corn Human Safety Genetically modified organ and soybeans— isms are used in are genetically modified, products made crop production because they are more from GMOs are not nutritious or because requir ed to be labele they are cheaper to produce But d in any way Chances are you ate a food these advantages come containing GMOs today, but the lack at a cost to the health of people consu of labeling means you ming GMOs? When probably can’t say for certain Labeli investigating complex questions like ng of foods containing this one, scientists often more than trace amounts of GMOs is use multiple experimental methods required in Europe, A 2012 animal study Japan, Australia, China, Russia, and involved 104 pigs that were divided into other countries Labeltwo groups: The ing advoc ates point out that the information would first was fed a diet containing 39% GMO allow corn and the other consumers to decide for themselves a closely related non-GMO corn The whether they wish to health of the pigs was be exposed to GMO foods Some biotec measured over the short term (31 days), hnology advocates, the medium term however, respond that similar deman (110 days), and the normal generational ds were not made when life span The re“transgenic” crop plants produced by searchers reported no significant differe traditi onal breeding nces between the two techniques were put on the market For groups and no traces of foreign DNA example, triticale (a in the slaughtered pigs crop used primarily in animal feed but Although pigs are a good model organ also in some human ism for human difoods) was created decades ago by combi gestion, critics argue that human data ning the genomes of are required to draw wheat and rye—two plants that not conclusions about the safe safety interbreed in nature f of dietary GMOs for people The Triticale is now sold worldwide withou results of one human study, study conducted jointly by Chinese t any special labeling and Scientists and the public need to weigh A Ameriican scient i ists, ts, were published in 2012 Sixty-eight the possible benChiefits versus risks on a case-by-case basis nese schoolchildren (ages 6–8) were The best scenario fed Golden Rice, spinach would be to proceed with caution, basing N New Scientific Thinking (a natural source of beta-caroten our decisions on a e), or a capsule containing sound scientific information rather than pure beta-carotene Over 221 days, blood on either irrational samples were drawn ttopics include: fear or blind optimism to measure how much h vitami vitam n A the body produced from each food source Thee data show that the beta-carotene in ▸ Module 2.15 — Scientists both study Why crop plants engineered to be resista Goldethe n Rice and d the ccapsules was converted to vitami nt to weed ? killermight n pose a danger to the environment A in the body with simila ? milar r efficie ncy, while the beta-carotene effects of rising atmospheric CO on in spinach led to signifi ificant cantly less vitamin A (Figure 12.9) The results led researchers tto conclu coral reef ecosystems de that GMO rice can indeed be effective in preven preve ting vitamin A deficiency Despi te its positive findings, this study caused an ▸ Module 8.10 — Tailoring treatment 75 uproar Chinese authorities called alled the th study an unethical “scandal,” complcancer to each patient may improve aining that U.S scientists had used Chine se schoolchildren as laboratory subjec 50 b cts bje ts The project leaders countered therapy that proper permission n and consent had been obtained in both China and the United nited States S The controversy highlights ▸ Module 25.3 — Coordinated one of waves the difficulties in 25 n condu cting research on human nutrition: Animal studie diess are of limited value, but human of movement in huddles help studies may be unethical cal T To date, no study has documented penguins thermoregulatehealth risks in humans fro ffrom m GMO foods, and there is genCapsule of pure Golden rice eral agreement among scientists that Spinach the GMO foods on the beta-carotene marke t are safe However, ▸ Module 26.3 — A widely used r iitt is i not yet possible to measure the weed ▲ Figure long-term effects (if any) 12.9 Vitamin A production after consumption of y) of GMO G s on human health different sources of beta-carotene killer demasculinizes maleEnviro frogs nmental Safety Adv Data from G Tang et al., Beta-carotene Advocates of a cautious approach in Golden Rice is as good as beta-car otene toward GMO crops fearr that transgenic in oil at providing vitamin A to children , American Journal of Clinical Nutrition plants might pass ▸ Module 29.2 — The model for 96(3): 658–64 (2012) Learn how to to thinkk like a scientist ▹ New Scientific Thinkingg modules explore how scientists use the processes of science for discovery Each module concludes with a question that challengess you to think like a scientist ntist Percentage absorbed and converted to vitamin A SCIENTIFIC THINKING ● The genes for herbicide resistance could transfer to closely related weeds, which could themselves then become resistant ▹ 240 magnetic sensory reception is incomplete CHAPTER 12 DNA Techno ology logy and a Genomics ◃ NEW! Scientific Thinking activities teach you how to practice important scientific skills like understanding variables and making predictions Specific wrong-answer feedback coaches you to the correct response To the Student: How to use this book and MasteringBiology® g gy Cycles rations and Plant Life ne Ge of n io at rn te Al ▹ 17.3 VISUALIZING THE CONCEPT modules walk you through challenging concepts and complex processes Haplo THE PLANT LIFE CYCLE uals— are diploid individ from ours Humans fro fr somes, two sets of chromo has us of h eac is, is that Gametes (sperm and ent (Module 8.12) cycle one from each par e in the human life stag loid hap s: The diploid eggs) are the only tion of generation rna alte an e ies hav Plants llular bod are distinct, multice es gametes and haploid stages ion of a plant produc The haploid generat loid generation dip The te etophy e In a hyt and is called the gam is called the sporop produces spores and alternate in se two generations the le, cyc life t’s plan all nonvascular er In mosses, as in obvious stage producing each oth is the larger, more te phy eto gam plants, the have a life cycle s, like most plants, ut of the life cycle Fern abo 95% of all sporophyte Today, dominated by the a dominant seed plants, have all g udin incl ts, plan cycles of all plants ir life cycle The life sporophyte in the e her wn sho tern pat follow a ▹ The brief narrative works together with the artwork to help you visualize and understand the topic Meiosis The life cycles of all plants follow the pattern shown Be sure that you understand this diagram; then review it after studying each life cycle to see how the pattern applies The sporophyte produces haploid spores by meiosis Sporophytee plant (2n) Egg (n) A sperm fertilizes an egg, resulting in a diploid zygote Fertilization Zygote (2n) The single-celled zygote divides by t e i s M ev mitosis and develop d r into a multicellula sporophyte In plants, gametes are produced by mitosis Mitosis nyy ony iony hion hi cushi n, cush reenn, h gree The The istss nsist moss wee see cons of gametophytes Sperm (n) Mit osi s d an ent m A Moss Life Cycle Hints embedded within the module emulate the guidance that you might receive during instructor office hours or in a tutoring session These hints provide additional information to deepen your understanding of the topic hyte The haploid gametop etes gam produces haploid mitosis by s) (sperm and egg re divides by A single-celled spo s mitosis and develop r llula tice mul Gametophyte into a p plant (n) gametophyte Spores (n) in The gametangium a male gametophyte rm spe es duc pro egg in Sperm swim to the gium the female gametan d d an nt sis me ito op M evel Diploid (2n) Haploid (n) Key os l o is a pm nd ent ▹ New Visualizing the Concept A Fe e cycles ns alternate in plant lif id and diploid generatio M dev itos elo is p Maximize your learning and success Sperm re A single-celled spo and divides by mitosis ticellular mul into s elop dev gametophyte Gametophyte plan The gametangium in a female gametophyte produces an egg ts (n) Spores (n) Sporangium grow Sporophytes (2n) s from gametophyte Egg n tion atio iliza Fertiliz Fert Sporophyte The sporophyte produces spores by meiosis in the sporangium ot The sporophyte cann is dependent photosynthesize—it on the gametophyte A sperm fertilizes the egg, producing a diploid zygote Zygote Gametophyte Meiosis 346 The Evolution of C H A P T E R 17 mitosis zygote divides by The single-celled rophyte a multicellular spo and develops into Mitosis and development In plants, meiosis produces spores Plant and Fungal Diversity IZ VISUALIZING NCEP THE NGGT LIZI AON ALIZING VISUUCAL VISUA EPPT THE CONCEP TTHE blood glucose level mones regulate blo ic horm Panncreattic omeos o glucagon maintains a ho secretion of insulin and systems ack sy f T o negative feedba ucose Tw “set point”” of glu bacck system ose in the blood One ffeedb amount of gluco it e raises it er he eas the oth whereas insulin, wher release of insulin ough release through thr e blood, glu the hen insulin is present in of glucagon Wh ored in live glucose is stto by nearly all cellls, and excess blood the n hen he glycogen Wh as a polysaccharride called okken down, and n stores are brok g glucagon, the glycoge ow illlustrates th lo figure belo returned to the blood The ample exaample aan exa man ma huma level, using a hum osse level glucos of blood gluc Insuulin release Beta ce release N OF BLOOD GLUCOOSE REGULLATION ood Rising blo se llevvell gluccose e the mulates stim ncreass pan nes ntagonistic hormo Effects of anta Gluccose n Insulin 0A 7:00 duuctioonn pproductio v evel lu s level glucose Stimu Carbo break roduct u goonn pro Glllucagon Glucagon el glucoose level r raises rai on release G Glucag Bl Concept Activities include interactive videos os that were created and narrated by the authors of the text mL) d lucose level (mg/100 ▹ NEW! Visualizing the 26.8 with dual functions: It secretes he pancreas is a gland TTh small intestine, and it secretes estive enzymes into the dige dig blood and glucagon, into the protein hormones, insulin two prot blood and ose in the blood glucose el of gluc level e the lev t egulat r regula mones r ho hor the These of glucose circulating through thereby control the amount f animal cells is an energy source for body Recall that glucose level is regulated ’ see how blood glucose Let’s endocrine pancreas are clusters of Scattered throughout the cells, which Within each islet are beta nsulin cells, called pancreatic islets n IInsulin e glucagon produce cells, which produc insulin and alpha cells e insulin, oduce produc pr because the es hormon be antagonistic in and glucagon are said to balance The other effects of the effects of one oppose the of the pancreas c Alpha cells g n into the blood glucago e gluc e release 2:00 PM ime g blood Declining evel glucose le e the mulates stim pancreas viii 2:00 PM Stimulus Lunch skipped e brea Liver cells glyccogen stores and gly return gllucose to the d blood Liver L e cells Pg No 346 C/M/Y/K l OF S4CARLISLE DESIGN SERVICES R es P blishing Servic CHAPTER Biology: Exploring Life S ? nowy owls (Bubo scandiacus), such as the one pictured below, are strikingly beautiful owls with bright orange eyes and wingspans as wide as five feet These swift and silent predators exhibit remarkable adaptations for life in their frozen, barren habitat The layers of fine feathers on their face, body, legs, and even their feet provide insulation in subzero weather They breed on the Arctic tundra, nesting on open ground The female broods the eggs and young, while the Why so many animals match male provides a steady supply of food His keen vision and acute hearing help him locate small mammals such as voles and lemmings, which he then snatches in midtheir surroundings? flight with his sharp talons The majority of owl species are nocturnal But during the endless days of arctic summers, snowy owls hunt in daylight Projecting upper eyelids help shield their eyes from bright sun As with all owls, the overlapping fields of vision of their forward-facing eyes provide superior depth perception These large eyes cannot move, so an owl must turn its whole head to follow a moving object This is not a problem for an owl, as you can see in the photo below, because adaptations of its neck BIG IDEAS Themes in the Study of Biology (1.1–1.4) Common themes help to organize the study of life ▹ vertebrae enable it to rotate its head a full 270 degrees Imagine being able to look over your left shoulder by turning your head to the right! You may think of owls in general in shades of brown, nesting in tree cavities and blending in with their surroundings And with snowy owls, you may think of Harry Potter’s white-feathered companion In real life, these owls also blend in with their wintry habitat Later in this chapter, you will read about an experiment that tests the hypothesis that camouflage coloration protects animals from predators The amazing adaptations of snowy owls are the result of evolution, the process that has transformed life from its earliest beginnings to the astounding array of organisms living today In this chapter, we begin our exploration of biology—the scientific study of life Evolution, the Core Theme of Biology (1.5–1.7) Evolution accounts for the unity and diversity of life and the evolutionary adaptations of organisms to their environment ▹ The Process of Science (1.8–1.9) In studying nature, scientists make observations, form hypotheses, and test predictions ▹ Biology and Everyday Life (1.10–1.11) Learning about biology helps us understand many issues involving science, technology, and society 39 ▹ Themes in the Study of Biology All forms of life share common properties Defining biology as the scientific study of life raises the obvious question: What is life? Even a small child realizes that a bug or a flower is alive, whereas a rock or a car is not But the phenomenon we call life defies a simple, one-sentence definition We recognize life mainly by what living things Figure 1.1 highlights seven of the properties and processes that we associate with life Order This sunflower illustrates the ordered structure that typifies life Living cells make up this complex organization Reproduction Organisms reproduce their own kind Here a baby African elephant walks beneath its mother Growth and development Inherited information in the form of DNA controls the pattern of growth and development of all organisms, including this hatching crocodile Energy processing This caterpillar will use the chemical energy stored in the plant it is eating to power its own activities and chemical reactions Regulation Many types of mechanisms regulate an organism’s internal environment, keeping it within limits that sustain life Pictured here is a lizard “sunbathing”—which helps raise its body temperature on cool mornings Response to the environment All organisms respond to environmental stimuli This Venus flytrap closed its trap rapidly in response to the stimulus of a damselfly landing on it (1) Order (5) Regulation ▲ Figure 1.1 Some important properties of life 40 CHAPTER Biology: Exploring Life (2) Reproduction Evolutionary adaptation A snowy owl’s sharp talons facilitate prey capture and its feathered feet keep it warm in its cold habitat Such adaptations evolve over many generations as individuals with traits best suited to their environment have greater reproductive success and pass their traits to offspring Figure 1.1 reminds us that the living world is wondrously varied How biologists make sense of this diversity and complexity, and how can you? Indeed, biology is a subject of enormous scope that gets bigger all the time One of the ways to help you organize this information is to connect what you learn to a set of themes that you will encounter throughout your study of life The next few modules introduce several important themes: novel properties emerging at each level of biological organization, the correlation of structure and function, and the exchange of matter and energy as organisms interact with the environment We then focus on the core theme of biology—evolution, the theme that makes sense of both the unity and diversity of life Let’s begin our journey with a tour through the levels of the biological hierarchy ? How would you define life? ● Life can be defined by a set of common properties such as those described in this module 1.1 (3) Growth and development (6) Response to the environment (4) Energy processing (7) Evolutionary adaptation 1.2 In life’s hierarchy of organization, new properties emerge at each level As Figure 1.2 illustrates, the study of life extends from the global scale of the biosphere to the microscopic level of molecules At the upper left we take a distant view of the biosphere, all of the environments on Earth that support life Ecosystem Florida Everglades Biosphere Florida Community All organisms in this wetland ecosystem Population All alligators living in the wetlands Organism an American alligator Nerve Brain Spinal cord Organ system Nervous system Organ Brain Tissue Nervous tissue These include most regions of land, bodies of water, and the lower atmosphere A closer look at one of these environments brings us to the level of an ecosystem, which consists of all the organisms living in a particular area, as well as the physical components with which the organisms interact, such as air, soil, water, and sunlight The entire array of organisms in an ecosystem is called a community In this community, we find alligators and snakes, herons and egrets, myriad insects, trees and other plants, fungi, and enormous numbers of microorganisms Each unique form of life is called a species A population includes all the individuals of a particular species living in an area Next in the hierarchy is the organism, an individual living thing, such as an alligator Within a complex organism, life’s hierarchy continues to unfold An organ system, such as the circulatory system or nervous system, consists of several organs that cooperate in a specific function For instance, the organs of the nervous system are the brain, the spinal cord, and the nerves An alligator’s nervous system controls all its actions An organ is made up of several different tissues, each in turn made up of a group of similar cells that perform a specific function A cell is the fundamental unit of life In the nerve cell shown here, you can see several organelles, such as the nucleus An organelle is a membrane-enclosed structure that performs a specific function within a cell Finally, we reach the level of molecules in the hierarchy A molecule is a cluster of small chemical units called atoms held together by chemical bonds Our example in Figure 1.2 is a computer graphic of a section of DNA (deoxyribonucleic acid)—the molecule of inheritance Now let’s work our way in the opposite direction in Figure 1.2, moving up life’s hierarchy from molecules to the biosphere At each higher level, there are novel properties that arise, properties that were not present at the preceding level For example, life emerges at the level of the cell—a test tube full of organelles is not alive Such emergent properties represent an important theme of biology The familiar saying that “the whole is greater than the sum of its parts” captures this idea The emergent properties of each level result from the specific arrangement and interactions of its parts ? Which of these levels of biological organization includes all others in the list: cell, molecule, organ, tissue? ● Organ Cell Nerve cell Nucleus Organelle Nucleus ▲ Figure 1.2 Atom Molecule DNA Life’s hierarchy of organization Themes in the Study of Biology 41 Cells are the structural and functional units of life 42 CHAPTER Biology: Exploring Life Prokaryotic cell Eukaryotic cell DNA (no nucleus) Membrane Organelles Nucleus (membraneenclosed) DNA (throughout nucleus) Colorized TEM 11,250× The cell has a special place in the hierarchy of biological organization It is the level at which the properties of life emerge—the lowest level of structure that can perform all activities required for life A cell can regulate its internal environment, take in and use energy, respond to its environment, and build and maintain its complex organization The ability of cells to give rise to new cells is the basis for all reproduction and also for the growth and repair of multicellular organisms All organisms are composed of cells They occur singly as a great variety of unicellular (single-celled) organisms, such as amoebas and most bacteria And cells are the subunits that make up multicellular organisms, such as owls and trees Your body consists of trillions of cells of many different kinds All cells share certain characteristics For example, every cell is enclosed by a membrane that regulates the passage of materials between the cell and its surroundings And every cell uses DNA as its genetic information However, we can distinguish h between two main forms of cells Prokaryotic cells were the first to evolve and were Earth’s sole inhabitants for more than 1.5 billion years Fossil evidence indicates that eukaryotic cells evolved from prokaryotic ancestral cells about 1.8 billion years ago Figure 1.3 shows these two types of cells as artificially colored photographs taken with an electron microscope A prokaryotic cell is much simpler and usually much smaller than a eukaryotic cell The cells of the microorganisms we call bacteria are prokaryotic Plants, animals, fungi, and protists (mostly unicellular organisms) are all composed of eukaryotic cells As you can see in Figure 1.3, a eukaryotic cell is subdivided by membranes into various functional compartments, or organelles These include a nucleus, which houses the cell’s DNA The properties of life emerge from the ordered arrangement and interactions of the structures of a cell Such a combination of components forms a more complex organization that we can call a system Systems and their emergent properties are not unique to life Consider a box of bicycle parts When all of the individual parts are properly assembled, the result is a mechanical system you can use for exercise or transportation The emergent properties of life, however, are particularly challenging to study because of the unrivaled complexity of biological systems Biologists today often use an approach called systems biology—the study of a biological system and the modeling of its dynamic behavior by analyzing the interactions among its parts Biological systems can range from the functioning of the biosphere to the molecular machinery of an organelle Cells illustrate another theme of biology: the correlation of structure and function Experience shows you that form ▲ Figure 1.3 Contrasting the size and complexity of prokaryotic and eukaryotic cells (shown here approximately 11,250 times their real size) generally fits function A screwdriver tightens or loosens screws, a hammer pounds nails Because of their form, these tools can’t each other’s jobs Applied to biology, this theme of form fitting function is a guide to the structure of life at all its organizational levels For example, the long extension of the nerve cell shown in Figure 1.2 enables it to transmit impulses across long distances in the body Often, analyzing a biological structure gives us clues about what it does and how it works The activities of organisms are all based on cells For example, your every thought is based on the actions of nerve cells, and your movements depend on muscle cells Even a global process such as the cycling of carbon is the result of cellular activities, including the photosynthesis of plant cells and the cellular respiration of nearly all cells, a process that uses oxygen to break down sugar for energy and releases carbon dioxide In the next module, we explore these processes and how they relate to the theme of organisms interacting with their environments ? Why are cells considered the basic units of life? ● They are the lowest level in the hierarchy of biological organization at which the properties of life emerge 1.3 Organisms interact with their environment, exchanging matter and energy An organism interacts with its environment, and that environment includes other organisms as well as physical factors Figure 1.4 is a simplified diagram of such interactions taking place in a forest in Canada Plants are the producers that provide the food for a typical ecosystem A tree, for example, absorbs water (H2O) and minerals from the soil through its roots, and its leaves take in carbon dioxide (CO2) from the air In photosynthesis, a tree’s leaves use energy from sunlight to convert CO2 and H2O to sugar and oxygen (O2) The leaves release O2 to the air, and the roots help form soil by breaking up rocks Thus, both organism and environment are affected by the interactions between them The consumers of a ecosystem eat plants and other animals The moose in Figure 1.4 eats the grasses and tender shoots and leaves of trees in a forest ecosystem in Canada To release the energy in food, animals (as well as plants and most other organisms) take in O2 from the air and release CO2 An animal’s wastes return other chemicals to the environment Another vital part of the ecosystem includes the small animals, fungi, and bacteria in the soil that decompose wastes and the remains of dead organisms These decomposers act as recyclers, changing complex matter into simpler chemicals that plants can absorb and use The dynamics of ecosystems include two major processes— the recycling of chemicals and the flow of energy These processes are illustrated in Figure 1.4 The most basic chemicals necessary for life—carbon dioxide, oxygen, water, and various minerals—cycle within an ecosystem from the air and soil to plants, to animals and decomposers, and back to the air and soil (shown with blue arrows in the figure) By contrast, an ecosystem gains and loses energy constantly Energy flows into the ecosystem when plants and other photosynthesizers absorb light energy from the sun (yellow arrow) and convert it to the chemical energy of sugars and other complex molecules Chemical energy (orange arrow) is then passed through a series of consumers and, eventually, to decomposers, powering each organism in turn In the process of these energy conversions between and within organisms, some energy is converted to heat, which is then lost from the system (red arrow) In contrast to chemicals, which recycle within an ecosystem, energy flows through an ecosystem, entering as light and exiting as heat In this first section, we have touched on several themes of biology, from emergent properties in the biological hierarchy of organization, to cells as the structural and functional units of life, to the exchange of matter and energy as organisms interact with their environment In the next section, we begin our exploration of evolution, the core theme of biology ? Explain how the photosynthesis of plants functions in both the cycling of chemicals and the flow of energy in an ecosystem ● Photosynthesis uses light energy to convert carbon dioxide and water to energy-rich food, making it the pathway by which both chemicals and energy become available to most organisms 1.4 ENERGY FLOW AL CYCLING CHEMIC Sun Inflow of light energy Outflow of heat Consumers (animals) Producers (plants) Leaves take up CO2 from air; roots absorb H2O and minerals from soil Chemical energy in food Decomposers such as worms, fungi, and bacteria return chemicals to soil ▲ Figure 1.4 The cycling of chemicals and flow of energy in an ecosystem Themes in the Study of Biology 43 ▹ Evolution, the Core Theme of Biology 1.5 The unity of life is based on DNA and a common genetic code Cell All cells have DNA, and the continuity of life depends forms of life use essentially the same genetic on this universal genetic material DNA is the chemical code to translate the information stored in substance of genes, the units of inheritance that trans- Nucleus DNA into proteins This makes it possible to mit information from parents to offspring Genes, which engineer cells to produce proteins normally DNA are grouped into very long DNA molecules called chrofound only in some other organism Thus, mosomes, also control all the activities of a cell bacteria can be used to produce insulin for How does the molecular structure of DNA account the treatment of diabetes by inserting a gene for its ability to encode and transmit information? for human insulin into bacterial cells C G Each DNA molecule is made up of two long chains, The diversity of life arises from differC G called strands, coiled together into a double helix The ences in DNA sequences—in other words, G C strands are made up of four kinds of chemical building from variations on the common theme of blocks Figure 1.5 (left side) illustrates these four build- G storing genetic information in DNA BacteC ing blocks, called nucleotides, with different colors and ria and humans are different because they letter abbreviations of their names The right side of have different genes But both sets of inT A the figure shows a short section of a DNA double helix structions are written in the same language Each time a cell divides, its DNA is first replicated, The entire “library” of genetic instrucA T or copied—the double helix unzips and new completions that an organism inherits is called C G mentary strands assemble along the separated strands its genome A typical human cell has two Thus, each new cell inherits a complete set of DNA, similar sets of chromosomes, and each set A T identical to that of the parent cell You began as a single contains about billion nucleotide pairs In cell stocked with DNA inherited from your two parents recent years, scientists have determined the The replication of that DNA entire sequence of nucleotides in the human T A during each round of cell divigenome, as well as the genomes of thousands A C G sion transmitted copies of the of other species More species continue to be G C DNA to what eventually became added to the list of species whose genomes the trillions of cells of your body T have been sequenced as the rate at which seC G The way DNA encodes a quencing can be done has accelerated rapidly cell’s information is analogous in recent years To deal with the resulting C A T to the way we arrange letters deluge of data, scientists are applying a sysof the alphabet into precise setems biology approach at the molecular level A T quences with specific meanings In an emerging field known as genomics, G T A The word rat, for example, conresearchers now study whole sets of genes jures up an image of a rodent; in a species and then compare genes across ▲ Figure 1.5 The four building blocks of DNA (left); tar and art, which contain the multiple species The benefits from such part of a DNA double helix (right) same letters, mean very differan approach range from identifying genes ent things We can think of the that may be implicated in human cancers to four building blocks as the alphabet of inheritance Specific revealing the evolutionary relationships among diverse organsequential arrangements of these four chemical letters encode isms based on similarities in their genomes Genomics affirms precise information in genes, which are typically hundreds or the unity of life based on the universal genetic material—DNA thousands of “letters” long In the next module, we see how biologists attempt to orgaThe DNA of genes provides the blueprints for making pronize the diversity of life teins, and proteins serve as the tools that actually build and maintain the cell and carry out its activities A bacterial gene What are the two main functions of DNA? ? may direct the cell to “Make a yellow pigment.” A particular human gene may mean “Make the hormone insulin.” All ● DNA is the genetic material that is passed from parents to offspring, and it codes for proteins that control the activity of cells 1.6 The diversity of life can be arranged into three domains We can think of biology’s enormous scope as having two dimensions The “vertical” dimension, which we examined in Module 1.2, is the size scale that stretches from molecules to 44 CHAPTER Biology: Exploring Life the biosphere But biology also has a “horizontal” dimension, spanning across the great diversity of organisms existing now and over the long history of life on Earth Colorized SEM 10,000× LM 340× Colorized SEM 7,500× Diversity is a hallmark of life Biologists have so Domain Bacteria Domain Archaea far identified and named about 1.8 million species Estimates of the total number of species range from 10 million to more than 100 million There seems to be a human tendency to group things, such as owls or butterflies, although we recognize that each group includes many different species And then we cluster groups into broader categories, such as birds and insects Taxonomy, the branch of biology that names and classifies species, arranges species into a hierarchy of broader and broader groups: genus, family, order, class, phylum, Bacteria Archaea and kingdom Historically, biologists divided all of life into Domain Eukarya five kingdoms But new methods for assessing evolutionary relationships, such as comparisons of DNA sequences, have led to an ongoing reevaluation of the number and boundaries of kingdoms Although the debate on such divisions continues, there is consensus among biologists that life can be organized into three higher levels called domains Figure 1.6 shows representatives of domains Bacteria, Archaea, and Eukarya Domains Bacteria and Archaea both consist of prokaryotes, organisms with prokaryotic cells Bacteria are the most diverse and widespread prokaryotes Many of the prokaryotes known as archaea Protists (multiple kingdoms) Kingdom Plantae live in Earth’s extreme environments, such as salty lakes and boiling hot springs Each rod-shaped or round structure in the photos of the prokaryotes in Figure 1.6 is a single cell These photos were made with an electron microscope, and the number along the side indicates the magnification of the image All the eukaryotes, organisms with eukaryotic cells, are grouped in domain Eukarya Protists are a diverse collection of mostly single-celled organisms Pictured in Figure 1.6 is an assortment of protists in a drop of pond water Biologists are currently assessing how to group the protists to reflect their evolutionary relationships Kingdom Fungi Kingdom Animalia The three remaining groups within Eukarya are distinguished partly by their modes of nutrition ▲ Figure 1.6 The three domains of life Kingdom Plantae consists of plants, which produce their own food by photosynthesis The plant pictured in Figure 1.6 is a tropical bromeliad, a plant native to shelter; the tree uses nutrients from the decomposition of the the Americas sloth’s feces; the prokaryotes gain access to the sunlight necesKingdom Fungi, represented by the mushrooms in sary for photosynthesis by living on the sloth; and the sloth is Figure 1.6, is a diverse group whose members mostly decamouflaged from predators by its green coat compose the remains of dead organisms and organic wastes The diversity of life and its interconnectedness are eviand absorb the nutrients into their cells dent almost everywhere Earlier we looked at life’s unity in Animals obtain food by eating other organisms The sloth its shared properties and common genetic code In the next in Figure 1.6 resides in South American rain forests There module, we explore how evolution explains both the unity are actually members of two other groups in the sloth photo and the diversity of life The sloth is clinging to a tree (kingdom Plantae), and the greenish tinge in its hair is a luxuriant growth of photosynthetic prokaryotes (domain Bacteria) This photograph exemTo which of the three domains of life we belong? plifies a theme reflected in our book’s title: connections be? tween living things The sloth depends on trees for food and ● Eukarya Evolution, the Core Theme of Biology 45 1.7 Evolution explains the unity and diversity of life Evolution can be defined as the process of change that has transformed life on Earth from its earliest beginnings to the diversity of organisms living today The fossil record documents the fact that life has been evolving on Earth for billions of years, and patterns of ancestry can be traced through this record For example, the mammoth being excavated in Figure 1.7A is clearly related to present-day elephants We can explain the shared traits of mammoths and elephants with the premise that they descended from a common ancestor in the distant past Their differences reflect the evolutionary changes that occurred within their separate lineages during the history of their existence on Earth Thus, evolution ▲ Figure 1.7A Excavation of accounts for life’s dual 26,000-year-old fossilized mammoth nature of kinship and bones from a site in South Dakota diversity This evolutionary view of life came into sharp focus in November gure 1.7B) 1859, when Charles Darwin (Figure mportant and published one of the most important en Entitled influential books ever written On the Origin of Species byy Means of Natural Selection, Darwin’s win’s book ller and was an immediate bestseller nonysoon made his name synonymous with the concept off evolution As a young man, Darwin made key observations that greatly influenced his thinking During a five-year, e, around-the-world voyage, ▲ Figure 1.7B he collected and docuCharles Darwin in 1859 mented plants and animals als láin widely varying locations—from the isolated Galáts of the pagos Islands off the coast of Ecuador to the heights Andes mountains to the jungles of Brazil He was particularly struck by the adaptations of these varied organisms ms that fit them to their diverse habitats After returning to England, Darwin spent more than two decades continuing his observations, er scientists, performing experiments, corresponding with other ed his work and refining his thinking before he finally published The first of two main points that Darwin presented in The Origin of Species was that species living today arose from a successor of ancestors that differed from them Darwin called this process “descent with modification.” It was an insightful 46 CHAPTER Biology: Exploring Life phrase, because it captured both the unity of life (descent from a common ancestor) and the diversity of life (modifications that evolved as species diverged from their ancestors) Figure 1.7C illustrates this unity and diversity among birds These three birds all have a common “bird” body plan of wings, beak, feet, and feathers, but these features are highly specialized for each bird’s unique lifestyle Darwin’s second point was to propose a mechanism for evolution, which he called natural selection Darwin started with two observations, from which he drew two inferences OBSERVATION #1: Individual variation Individuals in a population vary in their traits, many of which are inherited from parents to offspring OBSERVATION #2: Overproduction of offspring All species can produce far more offspring than the environment can support Competition for resources is thus inevitable, and many of these offspring fail to survive and reproduce INFERENCE #1: Unequal reproductive success Individuals with heritable traits best suited to the local environment are more likely to survive and reproduce than are less well-suited individuals INFERENCE #2: Accumulation of favorable traits over time As a result of this unequal reproductive success over many generations, a higher and higher proportion of individuals in the population will have the advantageous traits ▲ Figure 1.7C Unity and diversity among birds Try This For each bird, describe some adaptations that fit it to its environment and way of life ➊ Population with varied inherited traits ➋ Elimination of individuals with certain ➌ Increasing frequency of traits that enhance survival and reproductive success traits and reproduction of survivors ▲ Figure 1.7D An example of natural selection in action Try This Describe what might happen if some of these beetles colonized a sand dune habitat Deinotherium Mammut Platybelodon Stegodon Mammuthus Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa) 34 24 5.5 104 Millions of years ago Years ago ▲ Figure 1.7E An evolutionary tree of elephants Try This Use this tree to determine when mastadons (in the genus Mammut) last shared a common ancestor with African elephants know and learn about life In the next module, we introduce scientific inquiry, the process we use to study the natural world ? Explain the cause and effect of unequal reproductive success ● Those individuals with heritable traits best suited to the local environment produce the greatest number of offspring Over many generations, the frequency of those adaptive traits increases in the population Figure 1.7D uses a simple example to show how natural selection works ➊ An imaginary beetle population has colonized an area where the soil has been blackened by a recent brush fire Initially, the population varies extensively in the inherited coloration of individuals, from very light gray to charcoal ➋ A bird eats the beetles it sees most easily, the light-colored ones This selective predation reduces the number of light-colored beetles and favors the survival and reproductive success of the darker beetles, which pass on the genes for dark coloration to their offspring ➌ After several generations, the population is quite different from the original one As a result of natural selection, the frequency of the darker-colored beetles in the population has increased Darwin realized that numerous small changes in populations as a result of natural selection could eventually lead to major alterations of species He proposed that new species could evolve as a result of the gradual accumulation of changes over long periods of time This could occur, for example, if one population fragmented into subpopulations isolated in different environments In these separate arenas of natural selection, one species could gradually divide into multiple species as isolated populations adapted over many generations to different sets of environmental factors The fossil record provides evidence of such diversification of species from ancestral species Figure 1.7E traces an evolutionary tree of elephants and some of their relatives (Biologists’ diagrams of evolutionary relationships generally take the form of branching trees, usually turned sideways and read from left to right.) You can see that the three living species of elephants are very similar because they shared a recent common ancestor (dating to about million years ago, which is relatively recent in an evolutionary timeframe) Notice that all the other close relatives of elephants are extinct—their branches not extend to the present (The mammoth being excavated in Figure 1.7A belonged to the genus Mammuthus, whose members became extinct less than 10,000 years ago.) If we were to trace this family tree back to about 60 million years ago, however, you would find a common ancestor that connects elephants to their closest living relatives—the manatees and hyraxes The fossil record, along with other evidence such as comparisons of DNA, allows scientists to trace the evolutionary history of life back through time All of life is connected, and the basis for this kinship is evolution—the core theme that makes sense of everything we Evolution, the Core Theme of Biology 47 ▹ The Process of Science 1.8 In studying nature, scientists make observations and form and test hypotheses Science is a way of knowing—an approach to understanding the natural world It stems from our curiosity about ourselves and the world around us At the heart of science is the process of inquiry, the search for information and explanations of natural phenomena Scientific inquiry usually involves making observations, forming hypotheses, and testing them Observations may be made directly or indirectly, such as with the help of microscopes and other instruments that extend our senses Recorded observations are the data of science You may think of data as numbers, but a great deal of scientific data are in the form of detailed, carefully recorded observations For example, much of our knowledge of snowy owl behavior is based on descriptive, or qualitative, data, documented in field notes, photographs, and videos Other types of data are quantitative, such as numerical measurements that may be organized into tables and graphs Collecting and analyzing a large number of specific observations can lead to generalizations based on inductive reasoning For example, “All organisms are made of cells” is an inductive conclusion based on the discovery of cells in every biological specimen observed over two centuries of time Observations often prompt us to ask questions and seek answers through the forming and testing of hypotheses A hypothesis is a proposed explanation for a set of observations A good hypothesis leads to predictions that can be tested by making additional observations or by performing experiments Deductive reasoning is used to come up with ways to test hypotheses Here, the logic flows from general premises to the specific results we should expect if the premises are correct If all organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans should be composed of cells (a prediction that can be tested) We all use hypotheses in solving everyday problems Let’s say you are preparing for a big storm that is approaching your area and find that your flashlight isn’t working That your flashlight isn’t working is an observation, and the question is obvious: Why doesn’t it work? Reasonable hypotheses are that the batteries are dead or the bulb is burned out Each of these hypotheses leads to predictions you can test with experiments For example, the dead-battery hypothesis predicts that replacing the batteries with new ones will fix the problem Figure 1.8 diagrams the results of testing these hypotheses An important point about scientific inquiry is that we can never prove that a hypothesis is true As shown in Figure 1.8, the burned-out bulb hypothesis is the more likely explanation in our hypothetical scenario But perhaps the old bulb was simply loose and the new bulb was inserted correctly We could test this hypothesis by trying another experiment— carefully reinstalling the original bulb If the flashlight still doesn’t work, the burned-out bulb hypothesis is supported by another line of evidence Testing a hypothesis in various ways provides additional support for a hypothesis and increases our confidence in it 48 CHAPTER Biology: Exploring Life Observation: Flashlight doesn’t work Question: Why doesn’t the flashlight work? Hypothesis #1: Batteries are dead Hypothesis #2: Bulb is burned out Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Test of prediction: Replace batteries Test of prediction: Replace bulb Results: Flashlight doesn’t work Hypothesis is contradicted Results: Flashlight works Hypothesis is supported ▲ Figure 1.8 An everyday example of forming and testing hypotheses A scientific theory is much broader in scope than a hypothesis and is supported by a large and usually growing body of evidence For example, the theory of evolution explains a great diversity of observations and is supported by multiple lines of evidence In addition, the theory of evolution has not been contradicted by any scientific data Another important aspect of science is that it is necessarily repetitive: In testing a hypothesis, researchers may make observations that call for rejecting the hypothesis or at least revising and further testing it This process allows biologists to circle closer and closer to their best estimation of how nature works As in all quests, science includes elements of challenge, adventure, and luck, along with careful planning, reasoning, creativity, cooperation, competition, and persistence Science is a social activity, with most scientists working in teams, which often include graduate and undergraduate students Scientists share information through peerreviewed publications, seminars, meetings, and personal 1.9 analysis and evaluation of data; the use of tools and technologies that have built and continue to expand scientific knowledge; and the communication of the results of scientific studies and the evaluation of their implications for society as a whole ? What is the main criterion for a scientific hypothesis? ● It must generate predictions that can be tested communication Scientists build on what has been learned from earlier research and often check each other’s claims by attempting to confirm observations or repeat experiments To help you better understand what scientists do, we include a Scientific Thinking module in each chapter These discussions will encompass several broad activities of science: the forming and testing of hypotheses using various research methods; the Hypotheses can be tested using controlled field studies Yo have undoubtedly observed that many animals You TABLE 1.9 RESULTS FROM CAMOUFLAGE EXPERIMENT m match their environment: white snowy owls in their SCIENTIFIC Number of Attacks aarctic habitat, toads the color of dead leaves, flounTHINKING d ders that blend in with the sandy sea floor From On Non% Attacks on NonOn Camouflaged camouflaged camouflaged these th observations, you might hypothesize that such Habitat Models Models Models l patterns have evolved as adaptations that protect color animals from predation Can scientists test this camouflage Beach (light 71% hypothesis? Let’s consider an experiment with two populahabitat) tions of mice that belong to the same species (Peromyscus Inland (dark 16 76% polionotus) but live in different environments habitat) The beach mouse lives along the Florida seashore, a habitat of white sand dunes with sparse clumps of beach grass Data from S N Vignieri et al., The selective advantage of crypsis in mice, Evolution 64: 2153–2158 (2010) The inland mouse lives on darker soil farther inland As you can see in Figure 1.9, there is a striking match between mouse coloration and habitat In 2010, biologist Hopi Hoekthe control group, and the mice with the non-native colorstra of Harvard University and a group of her students ation were the experimental group Signs of predation were headed to Florida to test the camouflage hypothesis They recorded for three days Judging by the bite marks and surreasoned that if camouflage coloration protects mice from rounding tracks, the researchers deterWhy so predators, then mice with coloration that did not match their mined the predators were likely foxes, habitat would be preyed on more heavily than the native mice many animals coyotes, owls, herons, and hawks that were well-matched to their environment As you can see by the results prematch their The researchers built 250 plastic models of mice and sented in Table 1.9, the noncamouflaged surroundings? painted them to resemble either beach or inland mice Equal models had a much higher percentage of numbers of models were placed randomly in both habitats predation attacks in both the beach and inland habitats The The models resembling the native mice in each habitat were data thus fit the key prediction of the camouflage hypothesis This study is an example of a controlled experiment, one that is designed to compare an experimental group (the noncamouflaged mice models) with a control Beach population Beach mice living Inland population Members of the on sparsely vegetated sand dunes along same species living about 30 km inland group (the camouflaged models that matched the the coast have light tan, dappled coats are darker in color mice native in each area) Ideally, in a controlled experiment the two groups differ only in the one factor the experiment is designed to test—in this case, coat color and its effect on the success of predators The experimental design left coloration as the only factor that could account for the higher predation rate on the noncamouflaged mice in both the beach and the inland habitats This study is also an example of a field study, one not done in a laboratory but out in nature Researchers tested their hypothesis using the natural habitat of the mice and their predators ? ● Camouflaged mice are more likely to survive and reproduce, passing their protective coloration to their offspring ▲ Figure 1.9 Beach mouse and inland mouse with their native habitat These two populations of mice belong to the same species, yet they have very different coloration How does natural selection explain these differences? The Process of Science 49 ▹ Biology and Everyday Life Evolution is connected to our everyday lives To emphasize evolution as the core theme of biology, w include an Evolution Connection module in each we EVOLUTION c in this text But how is evolution connected CONNECTION chapter t your everyday life? to You just learned that natural selection is the primary mechanism of evolution, in which the environment “selects” for adaptive traits when organisms with such traits are better able to survive and reproduce Through the selective breeding of plants and animals, humans are also an agent of evolution As a result of artificial selection, our crops, livestock, and pets bear little resemblance to their wild ancestors Humans have been modifying species for millennia, and recent advances in biotechnology have increased our capabilities Plant biologists using genomics can identify beneficial genes in relatives of our crop plants, enabling the breeding or genetic engineering of enhanced crops Genes from totally unrelated species have also been inserted into plants For example, genes for such traits as drought or flood tolerance, improved growth, and increased nutrition have been engineered into rice plants (Figure 1.10) But humans also affect evolution unintentionally The impact of habitat loss and global climate change can be seen in the loss of species Indeed, scientists estimate that the current rate of extinction is 100 to 1,000 times the typical rate seen in the fossil record Our actions are also driving evolutionary changes in species For example, our widespread use of antibiotics and pesticides has led to the evolution of antibiotic resistance in How might an understanding of evolution contribute to the development of new drugs? Biology, technology, and society are connected in important ways M Many of the current issues facing society are related tto biology, and they often involve our expandCONNECTION iing technology What are the differences between sscience and technology? The goal of science is to understand un natural phenomena In contrast, the goal t h off technology is to apply scientific knowledge for some specific purpose Scientists usually speak of “discoveries,” whereas engineers more often speak of “inventions.” These two fields, however, are interdependent Scientists use new technology in their research, and scientific discoveries often lead to the development of new technologies The potent combination of science and technology can have dramatic effects on society For example, the discovery of the structure of DNA by Watson and Crick 60 years ago and subsequent advances in DNA science led to the technologies of DNA manipulation that today are transforming applied fields such as medicine, agriculture, and forensics Technology has improved our standard of living in many ways, but not without consequences Technology has helped Earth’s population to grow tenfold in the past three centuries 50 ? CHAPTER Biology: Exploring Life and more than double to billion in just the past 40 years Global climate change, toxic wastes, deforestation, and nuclear accidents are just some of the repercussions of more and more people wielding more and more technology Science can help identify problems and provide insight into how to slow down or prevent further damage But solutions to these problems have as much to with politics, economics, and cultural values as with science and technology Every citizen has a responsibility to develop a reasonable amount of scientific literacy to be able to participate in the debates regarding science and technology The crucial science-technology-society relationship is a theme we will return to throughout this text We hope this book will help you develop an appreciation for biology and help you apply your new knowledge to evaluating issues ranging from your personal health to the wellbeing of the whole world ? How science and technology interact? ● New scientific discoveries may lead to new technologies; new technologies may increase the ability of scientists to discover new knowledge 1.11 bacteria and pesticide resistance in insects How can evolutionary theory help address such worldwide problems? Understanding evolution can help us develop strategies for conservation efforts and prompt us to be more judicious in our use of antibiotics and pesticides It can also help us create flu vaccines and HIV drugs by tracking the rapid evolution of these ▲ Figure 1.10 Researcher working with viruses Identifying shared transgenic rice genes and studying their actions in closely related organisms may produce new knowledge about cancer or other diseases and lead to new medical treatments New sources of drugs may be found by tracing the evolutionary history of medicinal plants and identifying beneficial compounds in their relatives Our understanding of evolution can yield many beneficial results ● As one example, we can test the actions of potential drugs in organisms that share our genes and similar cellular processes 1.10 CHAPTER For practice quizzes, BioFlix animations, MP3 tutorials, video tutors, and more study tools designed for this textbook, go to REVIEW Reviewing the Concepts The Process of Science (1.8–1.9) Themes in the Study of Biology (1.1–1.4) 1.8 In studying nature, scientists make observations and form and test hypotheses Scientists use inductive reasoning to draw 1.1 All forms of life share common properties Biology is the scientific study of life Properties of life include order, reproduction, growth and development, energy processing, regulation, response to the environment, and evolutionary adaptation 1.2 In life’s hierarchy of organization, new properties emerge at each level Biological organization unfolds as follows: biosphere ecosystem community population organism organ system organ tissue cell organelle molecule Emergent properties result from the interactions among component parts 1.3 Cells are the structural and functional units of life Eukaryotic cells contain membrane-enclosed organelles, including a nucleus Prokaryotic cells lack such organelles Structure is related to function at all levels of organization Systems biology models the complex behavior of biological systems 1.4 Organisms interact with their environment, exchanging matter and energy Ecosys- ENERGY FLOW AL CHEMIC CYCLING Light general conclusions from many observations They form hypotheses and use deductive reasoning to make predictions, which can be tested with experiments or additional observations Data may be qualitative or quantitative A scientific theory is broad in scope and is supported by a large body of evidence 1.9 Hypotheses can be tested using controlled field studies Researchers found that mice models that did not match their habitat had higher predation rates than camouflaged models In a controlled experiment, the use of control and experimental groups can demonstrate the effect of a single variable Biology and Everyday Life (1.10–1.11) 1.10 Evolution is connected to our everyday lives Evolutionary theory is useful in medicine, agriculture, forensics, and conservation Human-caused environmental changes are powerful selective forces that affect the evolution of many species 1.11 Heat tems are characterized by the cycling of chemicalss from the atmosphere and Consumer n- Producers soil through producers, consumers, decomposers, and Chemical back to the environment energy ugh Energy flows one way through an ecosystem—entering as sunlight, converted to chemical energy by producers, passed on to consumers, and exiting as heat Biology, technology, and society are connected in important ways Technological advances stem from scientific research, and research benefits from new technologies Connecting the Concepts Complete the following map organizing some of biology’s major concepts Biology is the study of Evolution, the Core Theme of Biology (1.5–1.7) (a) 1.5 The unity of life is based on DNA and a common genetic code DNA is responsible for hered- has changed through the process of ity and for programming the activities of a cell A species’ genes are coded in the sequences of the four building blocks making up DNA’s double helix Genomics is the analysis and comparison of genomes (b) mechanism is depends on accounts for 1.6 The diversity of life can be arranged into three domains Taxonomists name species and classify them into a system of broader groups Domains Bacteria and Archaea consist of prokaryotes The eukaryotic domain, Eukarya, includes various protists and the kingdoms Fungi, Plantae, and Animalia 1.7 Evolution explains the unity and diversity of life Darwin synthesized the theory of evolution by natural selection Observations Inferences Heritable variations Natural selection: Unequal reproductive success leads to evolution of adaptations in populations Overproduction of offspring DNA (genetic code) (c) leads to codes for accounts for is evidence of (d) diversity of life seen in (e) seen in variations in cells as basic units of life seen in common properties of living organisms Chapter Review 51 Level 1: Knowledge/Comprehension The species of bacteria residing on your skin make up a an ecosystem b a community c a population d the biosphere Life is grouped into three domains based on a how individuals look under a microscope b the phenotypes of individuals c the methods for assessing evolutionary relationships, such as comparisons of DNA sequences d the different environments individuals live in Which of the following statements best distinguishes hypotheses from theories in science? a Theories are hypotheses that have been proved b Hypotheses usually are narrow in scope; theories have broad explanatory power c Hypotheses are tentative guesses; theories are correct answers to questions about nature d Hypotheses and theories are different terms for essentially the same thing in science Which of the following best demonstrates the unity among all living organisms? a descent with modification b DNA and a common genetic code c emergent properties d natural selection A controlled experiment is one that a proceeds slowly enough that a scientist can make careful records of the results b keeps all variables constant c is repeated many times to make sure the results are accurate d tests experimental and control groups in parallel Which mechanism of evolution did Darwin propose? a natural selection b genetic drift c evolution due to random mutations in DNA d migration and gene flow Level 2: Application/Analysis A biologist studying interactions among the protists in an ecosystem could not be working at which level in life’s hierarchy? (Choose carefully and explain your answer.) a the population level b the molecular level c the organism level d the organ level Which of the following best describes the logic of scientific inquiry? a If I generate a testable hypothesis, tests and observations will support it b If my prediction is correct, it will lead to a testable hypothesis c If my observations are accurate, they will support my hypothesis d If my hypothesis is correct, I can expect certain test results 52 CHAPTER Biology: Exploring Life 10 In an ecosystem, how is the movement of energy similar to that of chemicals, and how is it different? 11 Explain the role of heritable variations in Darwin’s theory of natural selection 12 What is a hypothesis, and how does it differ from a scientific theory? 13 Contrast technology with science Give an example of each to illustrate the difference 14 Biology can be described as having both a vertical scale and a horizontal scale Explain what that means Level 3: Synthesis/Evaluation 15 Explain what is meant by this statement: Natural selection is an editing mechanism rather than a creative process 16 The graph below shows the results of an experiment in which mice learned to run through a maze 25 Average time to complete maze (min) Testing Your Knowledge 20 15 10 No reward Food reward 0 Day a State the hypothesis and prediction that you think this experiment tested b Which was the control group and which the experimental? Why was a control group needed? c List some variables that must have been controlled so as not to affect the results d Do the data support the hypothesis? Explain 17 SCIENTIFIC THINKING Consider the camouflage experiment described in Module 1.9 Suppose that a group of researchers conducted a similar experiment with 10 live mice instead of 250 plastic models In this experiment, all of the camouflaged and noncamouflaged mice were killed The researchers concluded that the camouflage hypothesis is false Do you think this conclusion is justified? Why or why not? 18 The fruits of wild species of tomato are tiny compared to the giant beefsteak tomatoes available today This difference in fruit size is almost entirely due to the larger number of cells in the domesticated fruits Plant biologists have recently discovered genes that are responsible for controlling cell division in tomatoes Why would such a discovery be important to producers of other kinds of fruits and vegetables? To the study of human development and disease? To our basic understanding of biology? 19 The news media and popular magazines frequently report stories that are connected to biology In the next 24 hours, record the ones you hear or read about in three different sources and briefly describe the biological connections in each story Answers to all questions can be found in Appendix ... successful textbooks She is coauthor of Campbell Biology, Tenth Edition, Campbell Biology in Focus, Campbell Essential Biology, and Campbell Essential Biology with Physiology, Fourth Edition Martha. .. Central Community College Lewis Deaton, University of Louisiana Lawrence DeFilippi, Lurleen B Wallace College James Dekloe, Solano Community College Veronique Delesalle, Gettysburg College Loren... these levels of biological organization includes all others in the list: cell, molecule, organ, tissue? ● Organ Cell Nerve cell Nucleus Organelle Nucleus ▲ Figure 1.2 Atom Molecule DNA Life’s