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РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS GENES ARE SELFISH MOLECULES PLANTS LIVE ON A DIFFERENT TIMESCALE ALL BODILY ACTIVITY DEPENDS ON TEMPERATURE SOLAR ENERGY IS BOTH WITHOUT LIMIT AND WITHOUT COST THE TIME HAS COME FOR SCIENCE TO BUSY ITSELF WITH THE EARTH ITSELF THE ECOLOGY BOOK FOOD IS THE BURNING QUESTION BIG IDEAS SIMPLY EXPLAINED THINK GLOBALLY, ACT LOCALLY WE ARE PLAYING DICE WITH THE NATURAL ENVIRONMENT IF YOU DO NOT KNOW THE NAMES OF THINGS, THE KNOWLEDGE OF THEM IS LOST WE ARE LIVING ON THIS PLANET AS THOUGH WE HAD ANOTHER ONE TO GO TO РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS FOREWORD BY TONY JUNIPER РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS DK US/LONDON ASSISTANT ART EDITORS Shreya Singal, Vidushi Gupta, Amrai Dua Fiona Plowman, Dorothy Stannard, Rachel Warren Chadd SENIOR EDITORS Helen Fewster, Camilla Hallinan SENIOR EDITOR Janashree Singha ASSISTANT EDITOR Isobel Rodel SENIOR ART EDITOR Duncan Turner EDITOR Aadithyan Mohan K. INDEXER Marie Lorimer AMERICANIZER Jill Hamilton ASSISTANT EDITORS Rishi Bryan, Tanya Singhal, Nonita Saha PROOFREADER Richard Beatty JACKET DESIGNER Suhita Dharamjit ADDITIONAL TEXT Shannon Webber, Marcus Weeks SENIOR DTP DESIGNERS Harish Aggarwal, Jagtar Singh original styling by ILLUSTRATIONS James Graham JACKET EDITOR Emma Dawson JACKET DESIGNER Surabhi Wadhwa-Gandhi JACKET DESIGN DEVELOPMENT MANAGER Sophia MTT DTP DESIGNERS Mohammad Rizwan, Bimlesh Tiwary STUDIO 8 First American Edition, 2019 PICTURE RESEARCHER Vishal Ghavri Published in the United States by DK Publishing, 1450 Broadway, 8th Floor, New York, New York 10018 PRODUCER, PRE-PRODUCTION Andy Hilliard JACKETS EDITORIAL COORDINATOR Priyanka Sharma Copyright © 2019 Dorling Kindersley Limited DK, a division of Pengui; n Random House LLC SENIOR PRODUCER Meskerem Berhane MANAGING JACKETS EDITOR Saloni Singh MANAGING EDITOR Angeles Gavira Guerrero PICTURE RESEARCH MANAGER Taiyaba Khatoon MANAGING ART EDITOR Michael Duffy PRE-PRODUCTION MANAGER Balwant Singh ASSOCIATE PUBLISHING DIRECTOR Liz Wheeler PRODUCTION MANAGER Pankaj Sharma ART DIRECTOR Karen Self MANAGING EDITOR Soma B. Chowdhury DESIGN DIRECTOR Philip Ormerod SENIOR MANAGING ART EDITOR Arunesh Talapatra PUBLISHING DIRECTOR Jonathan Metcalf TOUCAN BOOKS DK DELHI EDI TORIAL DIRECTOR Ellen Dupont SENIOR ART EDITOR Ira Sharma SENIOR DESIGNER Thomas Keenes PROJECT ART EDITOR Vikas Sachdeva SENIOR EDITOR Scarlett O’Hara ART EDITORS Shipra Jain, Sourabh Challariya, Debjyoti Mukherjee EDITORS John Andrews, Alethea Doran, Sue George, Guy Croton, Cathy Meeus, Abigail Mitchell, Foreword © 2019 Tony Juniper 19 20 21 22 23 10 9 8 7 6 5 4 3 2 1 001–311040–Apr/2019 All rights reserved. Without limiting the rights under the copyright reserved above, no part of this publication may be reproduced, stored in or introduced into a retrieval system, or transmitted, in any form, or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior written permission of the copyright owner. Published in Great Britain by Dorling Kindersley Limited A catalog record for this book is available from the Library of Congress. ISBN 978-1-4654-7958-7 DK books are available at special discounts when purchased in bulk for sales promotions, premiums, fund-raising, or educational use. For details, contact: DK Publishing Special Markets, 1450 Broadway, 8th Floor, New York, New York 10018 or SpecialSales@dk.com Printed and bound in Malaysia A WORLD OF IDEAS: SEE ALL THERE IS TO KNOW www.dk.com РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS CONTRIBUTORS JULIA SCHROEDER, CONSULTANT DEREK HARVEY Julia Schroeder received her Ph.D. in Animal Ecology from the University of Groningen in the Netherlands. From 2012 to 2017, she headed a research group at the Max Planck Institute for Ornithology in Germany, studying social behavioral ecology. Julia currently researches and teaches evolutionary biology at Imperial College London. A naturalist and teacher with a particular interest in evolutionary biology, Derek Harvey graduated in Zoology from Liverpool University in the UK. He has taught a generation of biologists and led student expeditions to Costa Rica, Madagascar, and Australasia. Derek now concentrates on writing and consulting for science and natural history books. CELIA COYNE TOM JACKSON Celia Coyne is a freelance writer and editor living in Christchurch, New Zealand. She is the author of Earth’s Riches and The Power of Plants and writes and edits articles on science and natural history for magazines, newspapers, journals, websites, and books in the UK, Australia, and New Zealand. Her aim is to make scientific subjects accessible to lay readers. A writer for 25 years, Tom Jackson is the author of about 200 nonfiction books for adults and children and has contributed to many more. Tom studied zoology at Bristol University, UK, and worked in zoos and as a conservationist before turning to writing about natural history and all things scientific. JOHN FARNDON The author of hundreds of books on science and nature for both children and adults, John Farndon studied geography at Cambridge University. He has written extensively on earth sciences and the environment, focusing in particular on conservation and ecology. His books include The Oceans Atlas, The Wildlife Atlas, How the Earth Works, and The Practical Encyclopedia of Rocks and Minerals. TIM HARRIS After studying Norwegian glaciers in college, Tim Harris traveled the world in search of unusual wildlife and extraordinary landscapes. He has explored the dunes of the Namib Desert, climbed Popocatépetl in central Mexico, camped in the Sumatran rain forest, and searched the frozen Sea of Okhotsk in Russia. He is a former Deputy Editor of Birdwatch magazine in the UK and has written books about nature for adults and children. ALISON SINGER Alison Singer is a Ph.D. candidate in Community Sustainability at Michigan State University, US, where she studies storytelling and science communication. She has a broad educational background in writing, ecology, and the social sciences. Alison has worked as an educator for environmental charities, and for the US Environmental Protection Agency. РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS CONTENTS 12 INTRODUCTION 34 THE STORY OF EVOLUTION We’ve discovered the secret of life The role of DNA 38 Genes are selfish molecules The selfish gene 20 22 23 Time is insignificant and never a difficulty for nature Early theories of evolution A world previous to ours, destroyed by catastrophe Extinction and change ECOLOGICAL PROCESSES 44 No vestige of a beginning —no prospect of an end Uniformitarianism 24 The struggle for existence Evolution by natural selection 32 Human beings are ultimately nothing but carriers for genes The rules of heredity 50 52 Lessons from mathematical theory on the struggle for life Predator–prey equations Existence is determined by a slender thread of circumstances Ecological niches Complete competitors cannot coexist Competitive exclusion principle 66 The fitness of a foraging animal depends on its efficiency Optimal foraging theory 68 Parasites and pathogens control populations like predators Ecological epidemiology 72 Why don’t penguins’ feet freeze? Ecophysiology 74 All life is chemical Ecological stoichiometry Fear itself is powerful Nonconsumptive effects of predators on their prey 54 Poor field experiments can be worse than useless Field experiments 76 56 More nectar means more ants and more ants mean more nectar Mutualisms ORDERING THE NATURAL WORLD 60 Whelks are like little wolves in slow motion Keystone species 82 In all things of nature there is something of the marvelous Classification of living things РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 84 By the help of microscopes nothing escapes our inquiry The microbiological environment 86 If you do not know the names of things, the knowledge of them is lost A system for identifying all nature’s organisms 88 “Reproductively isolated” are the key words Biological species concept 90 Organisms clearly cluster into several primary kingdoms A modern view of diversity 92 Save the biosphere and you may save the world Human activity and biodiversity 96 We are in the opening phase of a mass extinction Biodiversity hotspots THE VARIETY OF LIFE 102 It is the microbes that will have the last word Microbiology 104 Certain tree species have a symbiosis with fungi The ubiquity of mycorrhizae 106 Food is the burning question Animal ecology 138 Life is supported by a vast network of processes Energy flow through ecosystems 140 The world is green Trophic cascades 144 Islands are ecological systems Island biogeography 150 It is the constancy of 114 Birds lay the number of eggs that produce the optimum number of offspring Clutch control 116 The bond with a true dog is as lasting as the ties of this earth can ever be Animal behavior 118 Redefine “tool”, redefine “man”, or accept chimpanzees as humans Using animal models to understand human behavior 126 All bodily activity depends on temperature Thermoregulation in insects ECOSYSTEMS 132 Every distinct part of nature’s works is necessary for the support of the rest The food chain 134 All organisms are potential sources of food for other organisms The ecosystem numbers that matters Ecological resilience 152 Populations are subjected to unpredictable forces The neutral theory of biodiversity 153 Only a community of researchers has a chance of revealing the complex whole Big ecology 154 The best strategy depends on what others are doing Evolutionarily stable state РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 156 Species maintain the functioning and stability of ecosystems Biodiversity and ecosystem function ORGANISMS IN A CHANGING ENVIRONMENT 162 The philosophical study of nature connects the present with the past The distribution of species over space and time 164 The virtual increase of the population is limited by the fertility of the country The Verhulst equation 166 The first requisite is a thorough knowledge of the natural order Organisms and their environment 167 Plants live on a different timescale The foundations of plant ecology 168 The causes of differences among plants Climate and vegetation 170 I have great faith in a seed Ecological succession 172 The community arises, grows, matures, and dies Climax community 174 An association is not an organism but a coincidence Open community theory 176 A group of species that exploit their environment in a similar way The ecological guild THE LIVING EARTH 198 The glacier was God’s great plow Ancient ice ages 178 The citizen 200 There is nothing 184 Population dynamics 202 Global warming isn’t a network depends on volunteers Citizen science become chaotic when the rate of reproduction soars Chaotic population change 185 To visualize the big picture, take a distant view Macroecology 186 A population of populations Metapopulations 188 Organisms change and construct the world in which they live Niche construction 190 Local communities that exchange colonists Metacommunities on the map to mark the boundary line Biogeography prediction. It is happening Global warming 204 Living matter is the most powerful geological force The biosphere 206 The system of nature Biomes 210 We take nature’s services for granted because we don’t pay for them A holistic view of Earth 212 Plate tectonics is not all havoc and destruction Moving continents and evolution 214 Life changes Earth to its own purposes The Gaia hypothesis РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 218 65 million years ago 270 The introduction something killed half of all the life on the Earth Mass extinctions of a few rabbits could do little harm Invasive species 274 As temperatures increase, the delicately balanced system falls into disarray Spring creep 224 Burning all fuel reserves will initiate the runaway greenhouse Environmental feedback loops THE HUMAN FACTOR 230 Environmental pollution is an incurable disease Pollution 236 God cannot save these trees from fools Endangered habitats 240 We are seeing the beginnings of a rapidly changing planet The Keeling Curve 280 One of the main threats 242 The chemical barrage has been hurled against the fabric of life The legacy of pesticides 248 A long journey from discovery to political action Acid rain 250 A finite world can support only a finite population Overpopulation 252 Dark skies are now blotted out Light pollution 254 I am fighting for humanity Deforestation 260 The hole in the ozone layer is a kind of skywriting Ozone depletion 262 We needed a mandate for change Depletion of natural resources 266 Bigger and bigger boats chasing smaller and fewer fish Overfishing to biodiversity is infectious diseases Amphibian viruses 281 Imagine trying to build a house while someone keeps stealing your bricks Ocean acidification 282 The environmental damage of urban sprawl cannot be ignored Urban sprawl 284 Our oceans are turning into a plastic soup A plastic wasteland 286 Water is a public trust and a human right The water crisis РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 306 The time has come for 324 We are playing dice with 308 Think globally, 326 Monocultures and science to busy itself with the Earth itself Environmental ethics act locally The Green Movement 310 The consequences of today’s actions on tomorrow’s world Man and the Biosphere Programme 312 Predicting a population’s ENVIRONMENTALISM AND CONSERVATION 296 The dominion of man over nature rests only on knowledge Humankind’s dominance over nature 297 Nature is a great economist The peaceful coexistence of humankind and nature 298 In wildness is the preservation of the world Romanticism, conservation, and ecology 299 Man everywhere is a disturbing agent Human devastation of Earth 300 Solar energy is both without limit and without cost Renewable energy size and its chances of extinction Population viability analysis the natural environment The economic impact of climate change monopolies are destroying the harvest of seed Seed diversity 328 Natural ecosystems and their species help sustain and fulfill human life Ecosystem services 330 We are living on this planet as though we have another one to go to Waste disposal 316 Climate change is happening here. It is happening now Halting climate change 322 The capacity to sustain the world’s population Sustainable biosphere initiative 332 DIRECTORY 340 GLOSSARY 344 INDEX 351 QUOTE ATTRIBUTIONS 352 ACKNOWLEDGMENTS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS FOREWORD As a small child, I was fascinated by nature—birds, butterflies, plants, reptiles, fossils, rivers, weather, and much else. My youthful passions set me on the path to being a life-long naturalist, and to working as an environmentalist, studying the natural world and promoting action for its conservation. I have worked as a field ornithologist, writer, campaigner, policy advocate, and environmental advisor. All of these diverse interests and activities have, however, been linked by a single theme: ecology. Ecology is a vast subject, embracing the many disciplines needed to understand the relationships that exist between different living things, and the physical worlds of air, water, and rock within which they are embedded. From the study of soil microorganisms to the role of pollinators, and from research into the water cycle to investigating Earth’s climate system, ecology involves many specialist areas. It also unites many strands of science, including zoology, botany, mathematics, chemistry, and physics, as well as some aspects of social science—especially economics—while at the same time raising profound philosophical and ethical questions. Because of the fundamental ways in which the human world depends on healthy natural systems, some of the most important political issues of our age are ecological ones. They include climate change, the effects of ecosystem damage, the disappearance of wildlife, and the depletion of resources, including fish stocks, freshwater, and soils. All these ecological changes have implications for people and are increasingly pressing. Considering the huge importance of ecology for our modern world, and the many threads of thought and ideas that must be woven to gain an understanding of the subject, I am delighted that Dorling Kindersley decided to produce The Ecology Book, setting out the key concepts that have helped shape our understanding of how Earth’s incredible natural systems function. In the pages that follow readers will also discover something about the history of ecological concepts, the leading thinkers, and the different perspectives from which they approached the questions they sought to answer. One thing that sets this book apart is the manner in which the rich, memorable, and attractive content is presented. A huge body of information and insight is effectively conveyed by clear layout, graphics, illustrations, and quotes, enabling readers to quickly achieve an understanding of many important ecological ideas and the people behind them: James Lovelock’s Gaia Hypothesis, Norman Myers’s warnings about impending mass extinction, and Rachel Carson’s work to expose the effects of toxic pesticides among them. The diverse body of information found in the pages that follow could not be more important. For while the headlines and popular debate suggest it is politics, technology, and economics that are the vital forces shaping our common future, it is in the end ecology that is the most important context determining societies’ prospects, and indeed the future of civilization itself. I hope you find The Ecology Book to be an enlightening overview of what is not only the most important subject, but also the most interesting. Tony Juniper CBE Environmentalist РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS INTRODU РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS CTION РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 14 INTRODUCTION F or the earliest humans, a rudimentary knowledge of ecology—how organisms relate to one another—was a matter of life and death. Without having a basic understanding of why animals grazed in a certain place and fruit-bearing plants grew in another, our ancestors would not have survived and evolved. How living animals and plants interact with each other, and with the nonliving environment interested the ancient Greeks. In the 4th century BCE, Aristotle and his student Theophrastus developed theories of animal metabolism and heat regulation, dissected birds’ eggs to discover how they grew, and described an 11-level “ladder of life,” the first attempt at classifying organisms. Aristotle also explained how some animals consume others—the first description of a food chain. In the Middle Ages (476–1500), the Catholic Church discouraged new scientific thought, and human understanding of ecology advanced very slowly. By the 16th century, however, maritime exploration, coupled with great technological advances, such as the invention of the microscope, led to the discovery of amazing life forms and a thirst for knowledge about them. Swedish botanist Carl Linnaeus developed a classification system, Systema Naturae, the first scientific attempt to name species and group them according to relatedness. Throughout this time, essentialism—the idea that each species had unalterable characteristics—continued to dominate Western thought. Great breakthroughs Geological discoveries in the late 17th and early 18th centuries began to challenge the idea of essentialism. Geologists noted that some fossil species suddenly disappeared from the geological record and were replaced by others, suggesting that There are some 4 million different kinds of animals and plants in the world. Four million different solutions to the problems of staying alive. David Attenborough organisms change over time, and even become extinct. The Frenchman Jean-Baptiste Lamarck proposed the first cohesive theory of evolution—the transmutation of species by the inheritance of acquired characteristics—in 1809. However, some 50 years later it was Charles Darwin—influenced by his experiences on the epic expedition of HMS Beagle—and Alfred Russel Wallace, who developed the concept of evolution by means of natural selection, the theory that organisms evolve over the course of generations to adapt better to their environment. Darwin and Wallace did not understand the mechanism by which this happened, but Gregor Mendel’s experiments on peas pointed at the role of hereditary factors later known as genes, representing another giant leap in evolutionary theory. Making connections The relationships between organisms and their environment, and between species, dominated ecological study in the early 20th century. The concepts of food chains and food webs (who eats what in a particular habitat) and ecological niches (the role an organism has in its environment) developed, and in 1935, Arthur РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS INTRODUCTION 15 Tansley introduced the concept of the ecosystem—the interactive relationship between living organisms and the environment in which they live. Later ecologists developed mathematical models to forecast population dynamics within ecosystems. Evolutionary theories also advanced with the discovery of the structure of DNA, and the evolutionary “vehicle” provided by mutation as DNA is replicated. New frontiers Improved technology opened up new possibilities for ecology. An electron microscope can now make images to half the width of a hydrogen atom, and computer programs can analyze the sounds made by bats and whales, which are higher or lower than can be heard by the human ear. Camera traps and infrared detectors photograph and film nocturnal creatures, and tiny satellite devices fitted to birds can track their movements. In the laboratory, analysis of the DNA of feces, fur, or feathers indicates which species an animal belongs to, and throws light on the relationship between different organisms. It is now easier than ever for ecologists to collect data, helped by a growing army of citizen scientists. New concerns Early ecology was driven by a desire for knowledge. Later, it was used to find better ways to exploit the natural world for human needs. As time went on, the consequences of this exploitation became increasingly evident. Deforestation was highlighted as a problem as early as the 18th century, and the problems of air and water pollution became obvious in industrialized nations in the 19th century. In 1962, Rachel Carson’s book Silent Spring alerted the world to the dangers of pesticides, and six years later Gene Likens demonstrated the link between power station emissions, acid rain, and fish deaths. In 1985, a team of Antarctic scientists discovered the dramatic depletion of atmospheric ozone over Antarctica. The link between greenhouse gases and a warming of Earth’s lower atmosphere had been made as early as 1947 by G. Evelyn Hutchinson, but it was decades before there was a scientific consensus on the man-made causes of climate change. The future Modern ecology has come a long way since the science was first recognized. It now draws on many disciplines. In addition to zoology, botany, and their microdisciplines, it relies on geology, geomorphology, climatology, chemistry, physics, genetics, sociology, and more. Ecology influences local and national government decisions about urbanization, transportation, industry, and economic growth. The challenges posed by climate change, rising sea levels, habitat destruction, the extinction of species, plastic and other forms of pollution, and a looming water crisis pose serious threats to human civilization. They demand radical policy responses based on sound science. Ecology will provide the answers. It is up to governments to apply them. ■ Even in the vast and mysterious reaches of the sea we are brought back to the fundamental truth that nothing lives to itself. Rachel Carson РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STO OF EVOL РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS RY UTION РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 18 INTRODUCTION James Hutton presents his theory that Earth is much older than was previously believed, and that Earth’s crust is continuously changing. In his Essay on the Theory of the Earth, Georges Cuvier suggests that fossils are the remains of extinct creatures wiped out by periodic “catastrophic” events. HMS Beagle sets sail on a circumnavigation of the world, with Charles Darwin serving as the voyage’s naturalist. The trip provides Darwin with the information that inspired his theory of evolution by natural selection. 1785 1813 1831 A 1809 1823 Jean-Baptiste Lamarck publishes Philosophie Zoologique, where he argues that animals acquire characteristics as a consequence of use or nonuse of different body parts, triggering mutations over generations. Amateur fossil hunter Mary Anning uncovers the first intact plesiosaurus skeleton. ncient myths, religions, and philosophies all reflect an enduring fascination with how the world began and man’s place in the story of life on Earth. In the West, Christianity held that all animals and plants were the result of a perfect creation. On the chain or ladder of being, no species could ever move from one position to another. Species were immutable, an idea called essentialism. The 18th-century Age of Enlightenment began to challenge orthodox Christian beliefs. French zoologist Jean-Baptiste Lamarck rejected the prevailing Bible-based notion of Earth being only a few thousand years old. He argued that organisms must have changed from simple life forms to more complex ones over millions of years, and that the “transmutation” of species was the driving force behind this change. He speculated that characteristics acquired by animals during their lifetime were inherited by the next generation: giraffes, for example, became slightly longernecked by stretching up to reach higher leaves, and passed this trait to their offspring; over many generations, giraffes grew longer and longer necks. Fossil evidence of extinct life forms with features that resembled modern descendants, found by pioneering geologists such as Georges Cuvier, also suggested Earth had more ancient origins. Meanwhile James Hutton and Charles Lyell argued that geological features could be accounted for by the constant, ongoing processes of erosion, and deposition—a view called uniformitarianism. Because these processes take place slowly, Earth’s history had to be much longer than was previously thought. Natural selection In 1858, Charles Darwin and Alfred Russel Wallace delivered a paper that would change biology forever. Darwin’s observations on the epic voyage of the Beagle (1831–36), his correspondence with other naturalists, and the influence of Thomas Malthus’s writings inspired Darwin’s insight that evolution came about by what he called natural selection. He spent 20 years gathering supporting data, but when Wallace wrote to him with the same idea, Darwin realized it was time to go public. His subsequent book, On the Origin of Species by Means of Natural Selection, provoked outrage. РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 19 Gregor Mendel’s paper “Experiments with Plant Hybrids” outlines findings from his pea plant experiments, laying the foundations for the field of genetics. The Selfish Gene by evolutionary biologist Richard Dawkins offers a new perspective on evolution, looking at the gene, as opposed to the species or group. 1866 1976 1859 1953 2003 Darwin elaborates on his theories of evolution in On the Origin of Species by Means of Natural Selection, which is an instant sellout. In The Eagle pub in Cambridge, UK, Crick and Watson announce that they have discovered the structure of DNA. The Human Genome Project produces the first genetic blueprint of Homo sapiens. Although the idea of evolution became widely accepted, the mechanism that made natural selection possible was not yet known. In 1866, an Austrian monk called Gregor Mendel made a huge contribution to genetics when he published his findings on heredity in pea plants. Mendel described how dominant and recessive traits pass from one generation to the next, by means of invisible “factors” that we now call genes. The rediscovery of Mendel’s work in 1900 initially sparked sharp debate between his supporters and many Darwinians. At the time, evolution was believed to be based on the selection of small, blending variations, but Mendel’s variations clearly did not blend. Three decades later, geneticist Ronald Fisher and others argued that the two schools of thought were complementary, rather than contradictory. In 1942, Julian Huxley articulated the synthesis between Mendel’s genetics and Darwin’s theory of natural selection in his book Evolution: The Modern Synthesis. The double helix Advances in technology such as X-ray crystallography led to more discoveries in the 1940s and ’50s, and the foundation of the new discipline of molecular biology. In 1944, chemist Oswald Avery identified deoxyribonucleic acid (DNA) as the agent for heredity. Rosalind Franklin and Raymond Gosling photographed strands of the DNA molecule in 1952, and James Watson and Francis Crick confirmed its double helix structure the following year. Crick then showed that genetic information is “written” on DNA molecules. The errors that occur when DNA copies itself create mutations—the raw materials for evolution. By the 1980s it was possible to map and manipulate the genes of individuals and species. In the 1990s, the mapping the human genome paved the way for medical research into gene therapy. Ecologists also want to establish whether genes influence behavior. Back in 1964, William D. Hamilton popularized the concept of genetic relatedness (“kin selection”) to explain altruistic behavior in animals. In The Selfish Gene (1976), Richard Dawkins further advanced the gene-centered approach. It is clear that aspects of evolutionary biology will still spark debate as long as ecologists continue to develop Darwin’s theory. ■ РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 20 TIME IS INSIGNIFICANT, AND NEVER A DIFFICULTY FOR NATURE EARLY THEORIES OF EVOLUTION IN CONTEXT KEY FIGURES The Comte de Buffon (1707–88), Jean-Baptiste Lamarck (1744–1829) BEFORE 1735 Swedish botanist Carl Linnaeus publishes Systema Naturae, a system of biological classification that later helped to determine species’ ancestry. 1751 In “Système de la nature” French philosopher Pierre Louis Moreau de Maupertuis introduces the idea that features can be inherited. AFTER 1831 Etienne Geoffroy SaintHilaire writes that sudden environmental change can cause a new species to develop from an existing organism. 1844 In Vestiges of the Natural History of Creation, Scottish geologist Robert Chambers argues—anonymously—that simple creatures have evolved into more complex species. B efore the 18th century, most people believed that plant and animal species stayed unchanged throughout time—a view now known as essentialism. This idea came under challenge as a result of two developments: the intellectual movement known as the Enlightenment (c. 1715–1800), and the Industrial Revolution (1760–1840). The Enlightenment was marked by scientific progress and increased questioning of religious orthodoxy, such as the claim that God created Earth and all living things in seven days. Then, as the Industrial Revolution gathered pace, canals, railroads, mines, and quarries cut through rock strata and revealed thousands of fossils, mostly of animal and plant species that no longer existed and had never been seen before. These suggested that life began long before the widely accepted creation date of 4400 bce, deduced from biblical sources. Animal adaptation In the late 1700s, French scientist Georges-Louis Leclerc, Comte de Buffon, upset church authorities by asserting that Earth was much older than the Bible suggested. He believed it was formed from molten material, struck off the Sun by a comet, that had taken 70,000 years to cool (a huge underestimate, in fact). As Earth cooled, species had appeared, died off, and were finally replaced by ancestors of those known today. Noting similarities among animals such as lions, tigers, and cats, Buffon deduced that 200 species of quadrupeds had evolved from just 38 ancestors. He also believed that changes in body shape and size in related species had occurred in response to living in different environments. In 1800, French naturalist JeanBaptiste Lamarck went further. In a lecture at the Museum of Natural Nature is the system of laws established by the Creator for the existence of things and for the succession of creatures. The Comte de Buffon РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 21 See also: Extinction and change 22 ■ Uniformitarianism 23 natural selection 24–31 ■ The rules of heredity 32–33 History in Paris, he argued that traits acquired by a creature during its lifetime could be inherited by its offspring—and that a buildup of such changes over many generations could radically alter an animal’s anatomy. Lamarck wrote several books in which he developed this idea of transmutation. He argued, for instance, that the use or nonuse of body parts eventually resulted in such features becoming stronger, weaker, bigger, or smaller in a species. For example, the ancestors of moles probably had good eyesight, but over generations this deteriorated because moles did not require vision as they burrowed underground. Similarly, giraffes gradually developed longer necks to enable them to reach leaves growing high up in trees. Drivers of evolution Larmarck’s ideas about inherited acquired traits were part of a wider early theory of evolution. He also believed that the earliest, simplest forms of life had emerged directly from nonliving matter. Lamarck identified two main “life forces” driving evolutionary change. One, he believed, made organisms ■ Evolution by …continuous use of any organ gradually strengthens, develops and enlarges that organ. Jean-Baptiste Lamarck Jean-Baptiste Lamarck develop from simple to more complex forms in a “ladder” of progress. The other, via the inheritance of acquired traits, helped them adapt better to their environment. When Charles Darwin developed his theory of evolution by means of natural selection, he would reject many of Lamarck’s ideas, but both men shared the belief that complex life evolved over an immense period of time. ■ Fossil finds changed ideas about how life began. The first example of an articulated plesiosaur—Plesiosaurus dolichodeirus—was discovered in 1823 by Mary Anning in Dorset, England. Born in 1744, Jean-Baptiste Lamarck attended a Jesuit college before joining the French army. Forced by an injury to resign, he studied medicine and then pursued his passion for plants, working at the Jardin du Roi (Royal Garden) in Paris. Supported by the Comte de Buffon, Lamarck was elected to the Academy of Sciences in 1779. When the Jardin’s main building became the new National Museum of Natural History during the French Revolution (1789–99), Lamarck was placed in charge of the study of insects, worms, and microscopic organisms. He coined the biological term “invertebrate” and often used the relatively simpler forms of such species to illustrate his “ladder” of evolutionary progress. However, Lamarck’s work was controversial and he died in poverty in 1829. Key works 1802 Research on the Organization of Living Bodies 1809 Zoological Philosophy 1815–22 Natural History of Invertebrate Animals РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 22 A WORLD PREVIOUS TO OURS, DESTROYED BY CATASTROPHE EXTINCTION AND CHANGE IN CONTEXT KEY FIGURE Georges Cuvier (1769–1832) BEFORE Late 1400s Leonardo da Vinci argues that fossils are the remains of living creatures, not just shapes spontaneously formed in the earth. 1660s English scientist Robert Hooke suggests that fossils are extinct creatures, since no similar forms can be found on Earth today. AFTER 1841 English anatomist Richard Owen calls huge reptile fossils “dinosaurs.” 1859 Charles Darwin’s On the Origin of Species explains how evolution can occur through “natural selection.” 1980 US scientists Luis and Walter Alvarez present evidence that an asteroid hit Earth at the time of the extinction of the dinosaurs. I n the early days of studying fossils, many people denied they could be extinct species. They failed to see why God would create and destroy creatures before humans ever appeared, arguing that unfamiliar fossil species might still be living somewhere on Earth. In the late 18th century, French zoologist Georges Cuvier looked into this by exploring the anatomy of living and fossil elephants. He proved that fossil forms such as mammoths and mastodons were anatomically distinct from living elephants, so they must represent extinct species. (It was highly unlikely that they still lived on Earth without being noticed.) Cuvier believed that Earth had experienced a series of distinct ages, each of which ended with a “revolution” that destroyed existing flora and fauna. He did not, though, believe that the evidence of fossil remains supported a theory of evolution. Nevertheless, Cuvier’s central views have continued to win support, and modern evidence points to at least five catastrophic mass extinction events in Earth’s past, including the one that wiped out the dinosaurs. Unlike Cuvier, however, today’s scientists know that life is not recreated out of nothing after a catastrophe. Rather, when a mass extinction event kills off many species, those left will evolve and multiply—sometimes relatively quickly—to fill vacant ecological niches, as the mammals did after the age of the dinosaurs. ■ Cuvier coined the name “mastodon” for its Greek meaning of “breast tooth,” referring to the nipplelike patterns on the creature’s teeth, which were unlike those of any living elephants. See also: Evolution by natural selection 24–31 ■ Ecological niches 50–51 ■ An ancient ice age 198–199 ■ Mass extinctions 218–223 РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 23 NO VESTIGE OF A BEGINNING, NO PROSPECT OF AN END UNIFORMITARIANISM IN CONTEXT KEY FIGURE James Hutton (1726–97) BEFORE 1778 The Comte de Buffon, a French naturalist, suggests that Earth is at least 75,000 years old—far older than most people believed at the time. 1787 German geologist Abraham Werner proposes that Earth’s layers of rock formed from a great ocean that once covered the entire planet. His followers became known as Neptunists. AFTER 1802 James Hutton’s theory of uniformitarianism reaches a wider audience when Scottish geologist John Playfair publishes Illustrations of the Huttonian Theory of the Earth. 1830–33 Principles of Geology, by Scottish geologist Charles Lyell, supports and builds on the uniformitarian ideas of James Hutton. U niformitarianism is the theory that geological processes, such as the laying down of sediment, erosion, and volcanic activity, occur at the same rate now as they did in the past. The idea emerged in the late 18th century, as mining, quarrying, and increased travel brought ever more geological features to light, including unusual rock strata and previously unknown fossils, whose origins were then widely debated. The generally accepted view that Earth was only a few thousand years old had been challenged by the Comte de Buffon, and in 1785 Scottish geologist James Hutton also argued for Earth’s far greater antiquity. Hutton’s ideas were formed during expeditions around Scotland to examine layers of rock. He believed that Earth’s crust was constantly changing, albeit mostly slowly, and could see no reason to suggest that the complex geological actions of layering, erosion, and uplifting took place faster in the distant past than they did in the present. Hutton also understood … from what has actually been, we have data for concluding [what] is to happen thereafter. James Hutton that most geological processes happen so gradually that the features he was discovering must be astronomically old. Uniformitarianism was not generally accepted at once, not least because it challenged a literal interpretation of the creation stories of the Old Testament. However, a new generation of geologists, such as John Playfair and Charles Lyell, threw their intellectual weight behind Hutton’s ideas, which also inspired a young Charles Darwin. ■ See also: Early theories of evolution 20–21 ■ Evolution by natural selection 24–31 ■ Moving continents and evolution 212–213 ■ Mass extinctions 218–223 РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STRUGGLE FOR EXISTENCE EVOLUTION BY NATURAL SELECTION РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 26 EVOLUTION BY NATURAL SELECTION IN CONTEXT KEY FIGURE Charles Darwin (1809–82) BEFORE 1788 In France, Georges-Louis Leclerc, Comte de Buffon, completes his 36-volume Histoire Naturelle, outlining early ideas about evolution. 1809 Jean-Baptiste Lamarck proposes that creatures evolve by inheriting acquired traits. AFTER 1869 Friedrich Miescher, a Swiss doctor, discovers DNA, although its genetic role is not yet understood. 1900 The laws of inheritance based on the pea plant experiments of Austrian scientist Gregor Mendel in the mid-1800s are rediscovered. 1942 British biologist Julian Huxley coins the term “modern synthesis” for the mechanisms thought to produce evolution. Charles Darwin N atural selection, a concept developed by British naturalist Charles Darwin and set out in his book On the Origin of Species by Means of Natural Selection (1859), is the key mechanism of evolution in organisms, resulting in different survival rates and reproductive abilities. Those organisms that have higher breeding success pass on their genes to more of the next generation, so individuals with these characteristics become more common. Natural selection is daily and hourly scrutinizing, throughout the world, the slightest variations. Charles Darwin To the Galapagos thousands of years. As Darwin looked at landscapes around the world that had been affected by processes of erosion, deposition, and volcanism, he began to speculate about animal species changing over very long time periods, and the reasons for such changes. By examining fossils and observing living animals, Darwin identified patterns; he noticed, for example, that extinct species had often been replaced by similar, but distinct, modern ones. Darwin’s field work on the islands of the Galapagos archipelago off South America in the fall Born in Shropshire, UK, in 1809, Darwin was fascinated by natural history from a young age. While at Cambridge University, he became friendly with several influential naturalists, including John Stevens Henslow. As a result, Darwin was invited to join the HMS Beagle expedition around the world. Henslow helped Darwin catalog and publicize his finds. Darwin’s research brought him fame and recognition—the Royal Society’s Royal Medal in 1853, nd fellowship of the Linnean Society in 1854. In 1859, his book On the Origin of Species sold out instantly. Despite continuing ill-health, Darwin fathered 10 children and never stopped studying and developing new theories. He died in 1882. The young Charles Darwin first began to consider evolution during his pioneering scientific expedition around the world aboard HMS Beagle from 1831 to 1836. As a young man, Darwin accepted the orthodox interpretation of the Bible, that Earth was only a few thousand years old. However, while he was on board the Beagle, Darwin read Scottish geologist Charles Lyell’s recently published Principles of Geology, in which Lyell demonstrated that rocks bore traces of tiny, gradual, and cumulative change over vast time periods—millions, rather than Key works 1839 Zoology of the Voyage of HMS Beagle 1859 On the Origin of Species by Means of Natural Selection 1868 The Variation of Animals and Plants under Domestication 1872 The Expression of Emotions in Man and Animals РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 27 See also: Early theories of evolution 20–21 ■ The rules of heredity 32–33 ■ The role of DNA 34–37 ■ The food chain 132–133 ■ Mass extinctions 218–223 ■ Population viability analysis 312–315 of 1835 provided especially strong evidence for his later theory of evolution by natural selection. Here, he observed that the shape of the carapaces (shells) of giant tortoises varied slightly from island to island. Darwin was also intrigued to find that there were four broadly similar, yet clearly distinct, varieties of mockingbirds, but that no single island had more than one species of the bird. He saw small birds, too, that looked alike but had a range of beak sizes and shapes. Darwin deduced that each group possessed a common ancestor but had developed diverse traits in different environments. Darwin’s conclusions On Darwin’s return to England, the differing beaks of the small birds he had found on the Galapagos, usually called “finches” although they are not in the true finch family, set him thinking. He knew that a bird’s beak is its key tool for feeding, so its length and shape offer clues to its diet. Later research revealed that there are 14 different finch species on the Galapagos islands. The differences in their beaks are marked and significant. For example, cactus finches have long, pointed beaks that are ideal for picking seeds out of cactus fruits, while ground finches have shorter, stouter beaks that are better suited for eating large seeds on the ground. Warbler finches have slender, sharp beaks, which are ideal for catching flying insects. Darwin speculated that the finches were descended from a common ancestral finch that had reached the archipelago from the mainland of South America. He concluded that a variety of finch ■ The selfish gene 38–39 Comparison of Galapagos finch bill structure Geospiza magnirostris The short, sharp bill of the Large Ground Finch, the biggest of Darwin’s finches, enables it to crack nuts. Geospiza fortis The bill of the Medium Ground Finch is variable, evolving rapidly to adapt to whatever size seeds are available. Geospiza parvula The stubby bill of the Small Tree Finch, which forages in foliage, suits its diet of seeds, fruits, and insects. Certhidea olivacea The slender, probing bill of the Green Warbler-finch helps it catch small insects and spiders. populations had evolved in different Galapagos habitats, each group adapted for a more or less specialist diet by a process that he would later call “natural selection.” Over time, the finch populations had become distinct species. In the early 21st century, researchers at Harvard University uncovered new evidence of how this happens at a genetic level. Their findings, published in 2006, showed that a molecule called calmodulin regulates the genes involved in shaping birds’ beaks, and is found at higher levels in longer-beaked cactus finches than in shorter-beaked ground finches. Malthus predicted that population growth would eventually outstrip food production. This idea matched the evidence Darwin had observed of ongoing competition between individual animals and species for resources. This competitive aspect formed the backbone of Darwin’s coalescing theory of evolution. By 1839, Darwin had developed an idea of evolution by natural selection. He was, though, reluctant to publish because he understood that the theory would unleash a storm of controversy from those who would view it as an attack on religion and the Church. When, in 1857, he began receiving communications from fellow British naturalist Alfred Russel Wallace, who had independently arrived at very similar conclusions, Darwin realized he had to publish his ❯❯ Refining the theory Darwin was influenced by Thomas Malthus’s An Essay on the Principle of Population (1798), in which РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 28 EVOLUTION BY NATURAL SELECTION ideas. Papers by Darwin and Wallace were jointly presented at a meeting of the Linnean Society of London in July 1858, under the title “On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection.. The following year, Darwin published the theory in On the Origin of Species by Means of Natural Selection. It offended some scientists because it differed from Lamarck’s ideas of transmutation, and also upset creationists who argued that it undermined a literal interpretation of the Bible. Others felt that the theory did not account for the huge range of characteristics in species and called it “unguided” and “nonprogressive.” Darwin was confident. He knew that all individual organisms in a species show a degree of natural variation; some have longer whiskers, or shorter legs, or brighter colors, for instance. Because members of all species compete for limited resources, he deduced that those whose traits are best suited to their environment are more likely to survive and reproduce. He also argued that characteristics that I see no good reasons why the views given in this volume should shock the religious views of anyone. Charles Darwin helped an individual organism live longer and reproduce more successfully would be passed on to more offspring, while those that made the organism less successful would be lost. Darwin called this “natural selection”—a process that, over generations, enabled a population of any given species to adapt better and thrive in its chosen habitat. Sexual selection Darwin also developed a theory of sexual selection. First outlined in On the Origin of Species, this was developed further in The Descent of Man, and Selection in Relation to Sex (1871). This theory was distinct from natural selection, as Darwin recognized that animals select mates based on characteristics that do not simply favor survival. For example, when Darwin considered the spectacular but cumbersome tails of male peafowl (peacocks), he could not imagine the tail playing any role in helping the individual bird to survive. He concluded that they were designed to boost an individual’s chance of reproductive success. Peahens choose males with the brightest tails, so the genetic material of these showy males is passed to the next generation. Bright tail feathers indicate that the bird is healthy, so choosing a mate with a bright tail is a good strategy for the peahen. However, Darwin’s idea that females choose a mate came under fire; 19th-century society could accept that males competed to reproduce (intrasexual selection), but intersexual selection, where one sex (usually the female) makes the choice, was ridiculed. Reproductive success is clearly essential for the future of a species. Natural selection is often described as “survival of the fittest,” but longevity alone is not particularly Natural selection There is variation in traits. For example, some beetles are pale and others dark. There is differential reproduction. No environment can support unlimited population growth, so some individuals lose out. Here, birds eat the pale beetles, so fewer of them reproduce. There is heredity. The dark beetles have more dark offspring because this trait has a genetic basis. End result: If darkness is the winning trait, producing more offspring, in time, all beetles will be dark. РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 29 Kin selection The peacock with the most splendid tail will attract the most peahens. Its bright tail will be passed on to its male offspring, which will find it similarly easy to attract mates. helpful. If individual A lives 10 times as long as individual B, but the latter produces twice as many offspring that then also breed, B will pass on more genes to the next generation than the longer-lived A. description of the scientific process. In 1930, British geneticist Ronald Fisher wrote The Genetical Theory of Natural Selection, which combined Darwin’s theory of natural selection with the ideas of heredity that the 19th-century Austrian scientist Gregor Mendel had developed. In 1937, Ukrainian– American geneticist Theodosius ❯❯ The term “kin selection” was first used by British biologist John Maynard Smith in 1964. It is the evolutionary strategy that favors the reproductive success of an organism’s relatives, prioritizing them above the individual’s own survival and reproduction. It occurs when an organism engages in self-sacrificial behavior that benefits its relatives. Charles Darwin was the first to discuss the concept when he wrote about the apparent paradox represented by altruistic nonbreeding social insects, such as worker honeybees, which leave reproduction to their mothers. British evolutionary biologist William Donald Hamilton proposed that bees, for example, behave in an altruistic manner—assisting others in reproduction—when the genetic closeness of the two bees and the benefit to the recipient outweigh the cost of altruism to the giver. This is called Hamilton’s Rule. Building on the theory Many of Darwin’s and Wallace’s ideas have proved remarkably accurate, despite the fact that the workings of genetics were not understood at the time. Although Darwin himself had used the term “genetic” as an adjective to describe the as-yet-unknown mechanism of inheritance, it was British biologist William Bateson, in the early 20th century, who first used the term “genetics” in a Why do some die and some live?… the answer was clearly, that on the whole the best fitted live. Alfred Russel Wallace In honeybee colonies, female worker bees look after the queen bee. They build the honeycomb, gather nectar and pollen, and feed larvae, but they do not breed. РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 30 EVOLUTION BY NATURAL SELECTION Albinism, as in this albino leopard gecko, is a mutation causing a lack of pigment. This mutation hinders the gecko’s chances of survival, making it lighter colored and sensitive to light. Dobzhansky put forward the idea that regularly occurring genetic mutations are sufficient to provide the genetic diversity—and therefore different traits—that makes natural selection possible. He wrote that evolution was a change in the frequency of an “allele” in the gene pool, an allele being one of the alternative forms of a gene that arise by mutation. A mutation is a permanent alteration in the sequence of deoxyribonucleic acid (DNA), the molecule that makes up a gene in one individual, resulting in a sequence that differs from that of other members of the species. Mutations may occur as the result of the miscopying of DNA during cell division, or they may be caused by environmental factors, such as damage resulting from the sun’s ultraviolet radiation. One mutation might affect only the individual organism carrying it, whereas another might affect all its offspring and future generations. Inherited mutations may or may not alter an individual’s phenotype – its physical traits and behavior. If mutations do affect the phenotype, they may be to its advantage or disadvantage, helping or hindering an organism’s ability to survive and reproduce successfully. If they hinder, they are likely to disappear from the population; if they help an organism adapt better to its environment, they become more common over the course of generations. Over time, they may produce large enough divergences from the parent population for a new species to evolve—a process called speciation. Mutation rates are usually very low, but the process is ever-present. The changes may be beneficial, neutral, or harmful. They do not occur in response to an organism’s needs, and are, in that respect, random. However, some types of mutations occur more frequently than others. Scientists now know, for example, that evolution can take place very rapidly in bacteria because of their frequent mutations. The vast majority of large mutations are deleterious; small mutations are both far more frequent and more likely to be useful. Ronald Fisher Different rates of evolution The ancestors of all life on Earth were very simple organisms. Recent scientific research suggest that the earliest “biogenic” rocks— derived from early life forms—date back nearly four billion years. In that time, highly complex life forms have evolved, and later fossils of species that look more similar to those of today reveal what has РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 31 Evolution in real time Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Theodosius Dobzhansky occurred. For example, a fossil record stretches back 60 million years for ancestors of the horse. The earliest of these were dogsized forest-dwelling animals with several toes on each foot. Evolution produced much larger horses with just a single hoof on each foot, adapted for life on open grasslands where they would often have had to outrun predators. Peppered moths (biston betularia) reveal change over a shorter period. The moth is usually pale, providing camouflage against the bark of birch trees, but a mutation produces some black moths. Before the 19th century, most peppered moths were pale. During the Industrial Revolution (1760–1840), however, smoky air left deposits of soot on trees and buildings in British cities, and the black form became much commoner. By 1895, 95 percent of peppered moths in Britain’s cities were black, as paler moths were eaten by birds because their coloring provided no camouflage. This phenomenon continues to act as an example of Darwin’s theory in action today, as the pale moth becomes common once more due to the declining soot concentrations in Britain’s cities. ■ Individuals within a species have a variety of forms of a characteristic. The individuals with the characteristic best suited to the environment are more likely to survive and breed. These characteristics are passed on to the next generation. Two peppered moths exhibit evolution at work, the lower one an example of industrial melanism. The dark variety began to appear in British cities in the early 1800s. Richard Lenski, a professor at Michigan State University, established the Long-term Experimental Evolution project in 1988. For more than 25 years, he studied 59,000 generations of the E. coli bacterium. During this time, he observed that the species used the glucose solution it lived in more efficiently, increasing in size but also growing faster. Also, a new species had evolved that was able to use a compound in the solution called citrate, which the parent bacterium could not. Evolving bacteria can pose a potential threat to humans. Increasing antibiotic use destroys many diseasecausing bacteria, but not those with mutations that make them resistant to the drugs. As the non-resistant bacteria are killed off, the resistant strains become more dominant, multiplying and passing on their mutations to future generations. That is natural selection at work. Escherichia (E.) coli bacteria can cause serious gut and other infections that will be increasingly difficult to treat as drug-resistant strains of E. coli multiply. РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 32 HUMAN BEINGS ARE ULTIMATELY NOTHING BUT CARRIERS FOR GENES THE RULES OF HEREDITY IN CONTEXT KEY ECOLOGIST Gregor Mendel (1822–84) BEFORE 1802 French biologist JeanBaptiste Lamarck suggests that traits acquired during the lifetime of an organism are transmitted to its offspring. 1859 Charles Darwin proposes his theory of evolution and natural selection in his book On the Origin of Species by Means of Natural Selection. AFTER 1869 Swiss chemist Friedrich Miescher identifies DNA, which he terms “nuclein.” 1953 Molecular biologists— including Briton Francis Crick and American James Watson—discover the structure of DNA. L ong before scientists cracked the genetic code, in 1866 an Austrian monk named Gregor Mendel was the first to show how traits are transferred through the generations. By means of much painstaking research, Mendel accurately predicted the basic laws of inheritance. When Mendel began his experiments, scientists believed that the various traits seen in plants and animals were handed down through a “blending” process. However, Mendel noticed that this was not the case when he was working in his monastery garden. When he crossed a plant that always produced green peas with one that always produced yellow peas, the result was not yellowishgreen peas—instead, all the peas were yellow. Mendel’s labors During the course of his research (1856–63), Mendel grew nearly 30,000 pea plants over several generations and carefully recorded the results. He focused on traits Mendel’s pea experiment Mendel’s experiment with growing peas proved that the gene carrying the yellow coloration was dominant while the gene for green was recessive. PARENT GENERATION 1 green 1 yellow all yellow F1 GENERATION 2000s Researchers in the field of epigenetics describe inheritance by mechanisms other than through the DNA sequence of genes. F2 GENERATION 1 green 3 yellows РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 33 See also: Early theories of evolution 20–21 ■ Evolution by natural selection 24–31 ■ The role of DNA 34–37 ■ The selfish gene 38–39 Heredity provides for the modification of its own machinery. James Mark Baldwin American psychologist dominant or recessive. When both inherited factors are dominant, the resulting plant will show the dominant trait. With a pair of recessive factors, the plant will show the recessive trait. However, if one dominant and one recessive factor are present, the plant will show the dominant trait. Pioneering geneticist (phenotypes) that had only two distinct forms—for example, white or purple flowers. When examining the trait of yellow or green peas, Mendel took green pea plants and cross-pollinated them with yellow pea plants. The peas produced from this parent generation were all yellow and Mendel named them the F1 generation. He then cross-pollinated pea plants from the F1 generation with each other to produce the F2 generation. He found that some peas produced were yellow and some were green. The F1 generation showed only one trait (yellow), which Mendel called “dominant.” However, in the F2 generation 75 percent had the dominant yellow trait and 25 percent displayed the nondominant —or “recessive”—green trait. Laws of inheritance Mendel theorized that every pea plant has two factors controlling each trait. When plants are crosspollinated, one factor is inherited from each plant. A factor can be Pea plants provided the raw data that Mendel used to develop his theories explaining the transmission of traits from one generation to the next. Mendel published his paper in 1866, but no one took much notice until 1900, when the botanists Hugo de Vries, Carl Erich Correns, and Erich Tschermak von Seysenegg discovered his work. Scientists then began proving Mendel’s theories more widely. Within just ten years, scientists named the pairs of factors “genes” and showed that they are linked on chromosomes. It is now known that inheritance is far more complex than Mendel recognized, but his meticulous research continues to form the basis for modern studies. ■ Gregor Johann Mendel Born Johann Mendel in 1822 on a farm in Silesia—then part of the Austrian Empire and now in the Czech Republic— Mendel studied philosophy and physics at the University of Olomouc (1840–43). At this time, he became interested in the work of Johann Karl Nestler, who was researching hereditary traits in plants and animals. In 1847 Mendel entered a monastery, where he was given the name Gregor. He then went on to study science further at Vienna University (1851–53). When Mendel returned to his monastery in 1853, the abbot Cyril Napp gave him permission to use the gardens for his research into hybridization. Mendel himself became an abbot in 1868 and no longer had time for his experiments. Although he never received credit for his discoveries during his lifetime, he is widely regarded as the founder of modern genetics. Key works 1866 “Experiments with Plant Hybrids,” Verhandlungen des naturforschenden Vereines in Brünn РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 34 WE’VE DISCOVERED THE SECRET OF LIFE THE ROLE OF DNA IN CONTEXT KEY FIGURES Francis Crick (1916–2004), Rosalind Franklin (1920– 58), James Watson (1928–), Maurice Wilkins (1916–2004) BEFORE 1910–29 US biochemist Phoebus Levene describes the chemical components of DNA. 1944 US researchers Oswald Avery, Colin Macleod, and Maclyn McCarty show that DNA determines inheritance. AFTER 1990 British researchers, led by embryologist Ian Wilmut, successfully clone an adult mammal—a sheep named Dolly. 2003 Scientists complete the mapping of the entire human genome. T he discovery of the structure of DNA (deoxyribonucleic acid) in 1953 is one of the most important scientific breakthroughs to date. It offered the key to understanding the very building blocks of life and explained how genetic information is stored and transferred. Englishman Francis Crick and American James Watson famously celebrated their joint discovery in a low-key fashion at their local pub in Cambridge, followed by a letter published in the journal Nature. Their discovery had enormous potential for scientific advances and had an important impact on many fields of research, from medicine to forensic science, taxonomy, and agriculture. The ramifications of their work still reverberate today, as methods of РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 35 See also: Early theories of evolution 20–21 ■ Evolution by natural selection 24–31 ■ The rules of heredity 32–33 selfish gene 38–39 ■ A system for identifying all nature’s organisms 86–87 ■ Biological species concept 88–89 Molecular biologists James Watson (left) and Francis Crick (right), pictured in 1953 with their double helix model of DNA. Watson called DNA “the most interesting molecule in all nature.” handling genetic material advance and we learn more about how individual genes operate. Crick and Watson’s breakthrough was the culmination of decades of research by numerous scientists, including Rosalind Franklin and Maurice Wilkins. While Crick and Watson worked with 3-D models to figure out how the components of DNA fitted together, at King’s Genetic engineering Understanding the structure of DNA has enabled scientists to change or “engineer” the genetic material in cells. It is possible to cut out a gene from one organism (the donor) and place it into the DNA of another organism. When this practice was first attempted in the 1970s it was both difficult and timeconsuming, but technological advances—such as Clustered Regularly Interspaced Short Palindromic Repeats, or CRISPR, which has been particularly College, London, Franklin and Wilkins were developing methods of X-raying DNA to view its structure. Watson had seen examples of Franklin’s work that hinted at DNA’s helical shape shortly before he and Crick announced their breakthrough. In 1962 Crick, Watson, and Wilkins were awarded the Nobel Prize for Physiology or Medicine. Franklin, who died in 1958, never received recognition for her part in the discovery during her lifetime, although Crick and Watson openly acknowledged that her work was essential to their success. ■ The DNA is like a computer program but far, far more advanced than any software ever created. Bill Gates DNA is a molecule featuring two long, thin strands that coil around each other to resemble a twisted ladder, in a shape known as a double helix. Using the ladder analogy, the sides of the ladder are made up of deoxyribose (a sugar) and phosphate, while the rungs of the ladder consist of paired nitrogenous bases, adenine (A), guanine (G), cytosine (C), and thymine (T). A always pairs up with T to form base pair AT, and G always pairs with C to form base pair GC. DNA is the blueprint for life. Sequences of bases along the DNA strand constitute the genes that provide the information that determines the complete form and physiology of an organism. A triplet of bases is known as a codon, and each codon specifies the production of one of 20 amino acids; the order in which the amino acids join together in a chain determines ❯❯ useful—have greatly simplified and accelerated the process. In theory, geneticists can now splice any gene with any other. They have attempted some intriguing combinations, such as the insertion of the gene for producing spider silk into goat DNA so that goats produce milk rich in proteins. Other substances that can be produced by modifying genes are hormones and vaccines. In gene therapy, a genetically modified vector (often a virus) is used to carry a gene into the DNA of an organism to replace a faulty or unwanted gene. A scientist analyzes a sample of DNA. Genetic manipulation in medicine is standard practice and DNA profiling is a vital forensic tool. Double helix structure РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 36 THE ROLE OF DNA Genetically modified food In agriculture, crops may be engineered to enhance them in some way. A genetically altered crop is known as a genetically modified organism (GMO). Companies that operate in this sector may modify a plant’s DNA so that it produces more of a certain nutrient or a toxin specific to a particular insect pest. The DNA of a plant may also be altered to become resistant to a particular herbicide, so that use of the chemical kills only the weeds and not the crop. Some ecologists argue that there is a risk of genetically unmodified plants becoming contaminated by GMOs. They also point out that the longterm effects of eating such foods are as yet not properly understood. Another concern is that in the future large agrochemical companies could control the world’s food supply by patenting the GMOs that they produce, to the detriment of poorer nations. New kinds of rice are being developed through genetic modification. This may improve the nutritional value of the crop or its resistance to disease. the type of protein they go on to make. For example, the combination GGA is the codon for glycine. Sixty-four possible triplets can be made from the four base pairs, and 61 of them code for a particular amino acid. The other three act as signals such as “start” and ”stop,” which govern how information is read by the cellular machinery. DNA is also organized into separate chromosomes, of which there are 23 pairs in the human cell. Copying the code When cells divide, DNA needs to be copied. This is achieved by the splitting of base pairs, which cuts The structure of DNA adenine thymine cytosine guanine A DNA molecule consists of a double helix formed by two strands, made up of sugars and phosphates, linked by paired base nucleotides: adenine and thymine or cytosine and guanine. the ladder down the middle to produce two single strands. These act as templates for the production of a second complementary DNA strand on each of them by matching up the appropriate base pairs. The process results in two strands of whole DNA that are exactly the same as the original. Since DNA remains in the nucleus of the cell, a related molecule called messenger ribonucleic acid (mRNA) copies segments of DNA coding sequence and carries the information to the regions of the cell where new proteins are made. RNA is chemically related to DNA, but the thymine base (T) is replaced by the base uracil (U), which is less stable but requires less energy to make. Stable living organisms benefit from having DNA genomes, but RNA makes up genomes of some viruses, where stability can be less advantageous. DNA is found in all living things on Earth, from amoebae to insects, to trees, tigers, and humans. Of course, the sequence of base pairs varies, and this difference allows geneticists to trace relationships between different species. Good and bad errors DNA is a highly stable molecule, but sometimes mistakes, known as mutations, occur. These can be in the form of an error, duplication, or omission in the order of the nucleotides A, C, G, and T. Mutation can be spontaneous—the result of errors that occur when the DNA is copied—or may be induced by external influences such as exposure to radiation or cancercausing chemicals. Some mutations have no effect, but others may change what the gene produces or inhibit the functioning of a gene. This can lead to problems in the organism as a whole. Examples РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 37 DNA barcoding of disorders caused by gene mutations include cystic fibrosis and sickle-cell disease. Although many mutations are harmful, occasionally a mutation will confer an advantage on an individual, enabling it to survive in its environment better than others of the same species. This type of mutation may end up being passed on through the process of natural selection. Over many generations, mutation is a mechanism for diversification, survival of the fittest, and ultimately evolution. The human genome On April 14, 2003, scientists completed the lengthy task of mapping (sequencing) the entire human genome. Geneticists worked out the precise position of all the base pairs in a chain of some three billion of the base nucleotides comprising an estimated 30,000 individual genes. This has allowed geneticists to identify new genes and the role they play in organisms. Armed with this knowledge, an individual can find out if they have inherited a faulty gene from a Mutated blood cells occur in sickle-cell disease—a genetic disorder passed on when both parents carry the faulty gene. It can be painful and increases the risk of serious infections. parent. Additionally, with access to such data it is possible to screen embryos for known genetic disorders before implantation in the womb. By March 2018, the DNA of around 15,000 organisms had been sequenced. Such information can help show how animals are related in the evolutionary line and how they have diversified. While the discovery of the composition and structure of DNA has revolutionized the science of heredity, it is worth noting that the regions of DNA used for coding proteins account for just 2 percent of the entire human genome. The nature of the other 98 percent is not yet fully understood by geneticists, but it is believed that at least some of these regions involve the regulation of the way genes are expressed, or activated. It seems that many more discoveries await future geneticists. ■ The idea of DNA barcoding was first raised in 2003 when a team at the University of Guelph, Canada, suggested that it would be possible to identify species by analyzing a common section of their DNA. Led by Dr. Paul Hebert, researchers chose a region in the gene known as cytochrome c oxidase 1 (“CO1”), made up of 648 base pairs. This region is quick to analyze, but the sequence is still long enough to differentiate between and within animal species. Different gene segments can be used for other forms of life. The first part of the barcoding system involves cataloguing samples of known species. The DNA is extracted and organized into a sequence of base pairs, a process known as “sequencing.” The sequence is then stored in a computer database, so that when a DNA sample from an unknown species is sequenced and entered into the database, the computer will match it with existing records. The barcoding technique has proved useful for taxonomy, helping classify animals and plants. With genetic engineering, we will be able … to improve the human race. Stephen Hawking РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 38 GENES ARE SELFISH MOLECULES THE SELFISH GENE IN CONTEXT KEY FIGURE Richard Dawkins (1941–) BEFORE 1963 British biologist William Donald Hamilton writes about the “selfish interests” of the gene in The Evolution of Altruistic Behaviur. 1966 American biologist George C. Williams proposes in his book Adaptation and Natural Selection that altruism is a result of selection taking place at the level of the gene. AFTER 1982 Richard Dawkins argues in The Extended Phenotype that the study of an organism should include analysis of how its genes affect the surrounding environment. 2002 Stephen Jay Gould critiques Dawkins’ theory in The Structure of Evolutionary Theory, which revisits and refines the ideas of classical Darwinism. T he concept of the “selfish gene” was popularized by British evolutionary biologist Richard Dawkins in his 1976 book of that name. It states that evolution is fundamentally based upon the survival of different forms of a particular gene at the expense of others. The forms that survive are those that are responsible for the bodily types and behaviors (phenotypic traits) that successfully promote their own propagation. Supporters of the theory argue that because heritable information is passed through the generations by the genetic material of DNA, both natural selection and evolution are best considered from the perspective of genes. Natural selection works toward the survival of the gene, not the individual. Male black widow spiders mate even though the females eat them immediately after. Animals that warn others of approaching predators sacrifice themselves at the expense of the wider group. Nonbreeding bees in bee colonies serve to help the community survive. РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS THE STORY OF EVOLUTION 39 See also: Evolution by natural selection 24–31 ■ The role of DNA 34–37 ■ Mutualisms 56–59 A male black widow spider gingerly approaches a huge female to mate. This genetically driven act will reproduce his genes but will lead to his death. Dawkins was strongly influenced by the work of William Donald Hamilton on the nature of altruism and closely examined the biology of selfishness and altruism in The Selfish Gene. He argued that organisms were simply vehicles that supported their genes, or “replicators.” Genes that help an organism survive and reproduce tend also to improve those genes’ own chances of being replicated. Successful genes often provide a benefit to the host organism. For example, a gene that protects an animal or plant against disease thereby helps that particular gene to spread. However, the interests of the replicator and the vehicle may sometimes seem to be in conflict. Genes drive the male black widow spider to mate despite the risk of being eaten by her. However, the male’s sacrifice nourishes the female and improves the prospect of his genes being passed on. Selfishness and altruism Gene selfishness usually gives rise to selfishness in the behavior of an individual organism, but there are ■ The rules of heredity 32–33 circumstances in which the gene can achieve its own selfish goals by fostering apparent altruism in the organism. One example is kin selection, the evolutionary strategy that favours the reproductive success of an individual organism’s relatives, even at the cost of the individual’s own reproduction or survival. An extreme example of genetically based altruism is eusociality. Honey bees are a eusocial species. They live in colonies which include breeding and non-breeding individuals. By helping the colony survive, the many thousands of non-breeding worker bees ensure the reproduction of the genes they have in common with the sole breeding individual, the queen. Critics of Dawkins’ theory argue that since individual genes do not control behaviour, they cannot be said to be acting selfishly. Dawkins has maintained that he never meant to suggest that genes had their own conscious will. He later wrote that “the immortal gene” might have been a better title for both his concept and the book. ■ The theory of evolution is about as much open to doubt as the theory that the Earth goes around the Sun. Richard Dawkins Richard Dawkins Richard Dawkins was born in Kenya to British parents. After the family returned to the UK, he developed a strong interest in the natural world and studied zoology at Oxford University. While there, he was tutored by Nobel Prizewinner Niko Tinbergen, who was a pioneer of animal behavior studies. After a brief period at the University of California at Berkeley, Dawkins returned to Oxford to lecture in zoology. Richard Dawkins is best known for his book The Selfish Gene, in which he argues that the gene is the principle unit of selection in evolution. His theory later triggered a series of fierce debates with Stephen Jay Gould and other evolutionary biologists. Dawkins is also known as a strong advocate of atheism and feminism. Key works 1976 The Selfish Gene 1982 The Extended Phenotype 1986 The Blind Watchmaker 2006 The God Delusion 2009 The Greatest Show on Earth: The Evidence for Evolution РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS ECOLOGI PROCESS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS CAL ES РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 42 INTRODUCTION Joseph Grinnell publishes his research on the California Thrasher, establishing the basis for the theory of ecological niches. Robert MacArthur’s research on North American warblers shows how different species can avoid directly competing with each other in order to coexist. Dan Janzen observes the interdependence of acacia trees and the ants that reside on them, and concludes that the species evolved in a mutualistic manner. 1917 1957 1965 I 1925–26 1961 1969 The Lotka-Volterra model uses a mathematical equation to describe the interactions between predator and prey. Joseph Connell reveals that different types of barnacle thrive in different tidal zones, although they could, in theory, live in any of them. Robert Paine coins the term “keystone species” to describe species that play a crucial role in ecosystem functions. n the 5th century BCE, the Greek historian Herodotus described watching crocodiles open their jaws for plovers to pick food from their teeth. He may have been the first to write about an ecological process—in this case a mutualistic relationship between reptiles and birds. Aristotle and Theophrastus observed many more interactions between animals and their environment in the 4th century BCE. Over the next two millennia, countless other observations of the natural world were made, but a deep understanding of how organisms interacted with each other and the world around them was hampered by the inability to observe very small things, those that were active at night, or those living underwater. Additionally, few people with an interest in nature experienced much beyond their own local area. As technology improved and people began to travel the world, scientists such as Robert Hooke, Antonie van Leeuwenhoek, Carl Linnaeus, Alexander von Humboldt, Alfred Russel Wallace, Charles Darwin, and Johannes Warming became increasingly aware of ecological processes and laid the foundations of the science of ecology, even if they didn’t use that word. Mathematical models It had long been understood that one of the most basic ecological processes is the struggle for survival: for herbivores to find food, predators to find prey, and prey to avoid being eaten. Predators do everything they can to hunt and eat prey, and the latter do all they can to avoid being eaten. In 1910, Alfred Lotka introduced one of the first mathematical models ever applied to ecology. Now known as the Lotka-Volterra model, its predator–prey equations help predict the population fluctuations of these two groups. In the early years of the 20th century, Joseph Grinnell conducted extensive research into animals’ habitat needs in the western United States. He observed that species had different “niches” within a habitat—and that if two species have approximately the same food requirements, one will “crowd out” the other. Darwin had observed this on his travels aboard HMS Beagle, but Grinnell’s axiom developed the idea further, as did subsequent research. In 1934, Georgy Gause demonstrated what he called the competitive exclusion principle in РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS ECOLOGICAL PROCESSES 43 Roy Anderson and Robert May demonstrate how epidemics affect animal population growth rates. Research published by Ronald Pulliam, Eric Charnov, and Graham Pyke expands on the optimal foraging theory that animals try to gather resources while wasting as little energy as possible. Robert Sterner and James Elser pioneer the study of ecological stoichiometry—how ratios of different chemicals within living organisms change with certain reactions. 1970s 1977 2002 1972 1991 Knut Schmidt-Nielsen publishes How Animals Work. The book hugely influences the field of ecophysiology. Earl Werner publishes his findings about nonconsumptive effects of predators on prey. laboratory projects. As William E. Odum put it in 1959, “the ecological niche of an organism depends not only on where it lives, but also on what it does.” From field to lab Laboratory experiments and field observations are the main methods of providing data for the study of ecological processes, but field experiments—in which a local environment is manipulated to test a hypothesis—were not conducted with scientific rigor until Joe Connell’s work with barnacles in Scotland. His experiments—the results of which were published in 1961—were meticulously planned and observed, and were repeatable. Connell set the “gold standard” for fieldwork, but experiments in laboratories still have a vital role to play, too—as Earl Werner demonstrated 30 years later. His work revealed the non-consumptive impact of predatory dragonfly larvae on the behavior and physical development of their tadpole prey. Since the mid-20th century, many new ideas on ecological processes have emerged. Work by Robert MacArthur and others on competition between species led to the development of optimal foraging theory, which seeks to explain why animals choose to eat some food items and not others. Mutualistic relationships became better understood through the research of biologists such as Daniel Janzen. Robert Paine’s work with starfish and mussels also highlighted the concept of keystone species— those that have a disproportionate influence on their ecosystems. New technology Technological advances—including sophisticated chemical sampling techniques, satellites with remote sensing equipment, and computers capable of rapidly processing huge quantities of data—have opened up new areas of study. Ecological stoichiometry, for example, studies the flow of energy and chemical elements throughout food webs and ecosystems, from the molecular level up. Like so many ideas in ecology, its origins can be traced back many years, but only took hold with Robert Sterner and James Elser’s 2003 book Ecological stoichiometry: The biology of elements from molecules to the biosphere. New techniques such as this will undoubtedly continue to deepen our understanding of processes in ecology. ■ РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS LESSONS FROM MATHEMATICAL THEORY ON THE STRUGGLE FOR LIFE PREDATOR–PREY EQUATIONS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 46 PREDATOR–PREY EQUATIONS IN CONTEXT KEY FIGURES Alfred J. Lotka (1880–1949), Vito Volterra (1860–1940) BEFORE 1798 British economist Thomas Malthus shows that the rate at which the population changes increases as the size of the population grows. 1871 In Lewis Carroll’s novel Through the Looking Glass, the Red Queen tells Alice, “you have to run just to stay in the same place.” AFTER 1973 American biologist Leigh Van Valen proposes the Red Queen effect, which describes the constant “arms race” between predators and prey. 1989 The Arditi–Ginzburg equations offer another model of predator–prey dynamics by including the impact of the ratio between predator and prey. Vito Volterra Populations of two species, one predator, the other prey, interact. The prey has access to food and its population growth is exponential. When prey animals meet a predator, they are eaten. Eating prey results in more predators. More predators results in less prey, reducing the number of predators. Born in 1860 in Ancona, Italy, the son of a Jewish cloth merchant, Vito Volterra grew up in poverty. Despite this, in 1883, aged just 23, he secured a position as professor of mechanics at the University of Pisa and began a career as a mathematician. Further professorships at the universities of Turin and Rome followed. In 1900, Volterra married, fathering six children, although only four survived to adulthood. He was made a senator of the Kingdom of Italy in 1905 and worked on the development of military airships during World War I. In 1931, T he predator–prey equations are an early example of the application of mathematics to biology. Formulated in the 1920s by American mathematician Alfred J. Lotka and Italian mathematician and physicist Vito Volterra, the two equations—also known as the Lotka–Volterra equations— describe the way in which the population of a predator species and that of its prey fluctuate in relation to each other. Lotka proposed the equations in 1910, as a way of understanding the rates of autocatalytic chemical reactions—chemical processes that regulate themselves. In the following decade, he applied the equations to the population dynamics of wild animals. In 1926, Vito Volterra arrived at the same conclusions. He had become interested in the subject after meeting Italian marine biologist Umberto D’Ancona. D’Ancona told Volterra how the percentage of predatory fish caught in nets in the Adriatic Sea had greatly increased during World War I. This change was clearly linked to the drastic reduction in fishing during the Volterra refused to swear loyalty to Italy’s fascist dictator Benito Mussolini and was dismissed from the University of Rome. Forced to work abroad, he only returned to Italy for a short time before his death in 1940. Key works 1926 “Fluctuations in the Abundance of a Species Considered Mathematically,” Nature 1935 Les associations biologiques au point de vue mathématique РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS ECOLOGICAL PROCESSES 47 See also: Evolution by natural selection 24–31 ■ The selfish gene 38–39 ■ Ecological niches 50–51 principle 52–53 ■ Mutualisms 56–59 ■ Keystone species 60–65 ■ Optimal foraging theory 66–67 A cheetah pursues a Thomson’s gazelle. The predator–prey equations are able to model the way populations of both species will change in response to the activities of the other. war years, but D’Ancona could not explain why less fishing did not produce more fish of all kinds in the nets. Using the same equations as Lotka, Volterra eventually explained the fluctuations in both the predator and the prey species. Population principles At the time Lotka and Volterra made their calculations, the science of population dynamics was still in its infancy, having barely moved on since the population studies of British economist Thomas Malthus in the late 18th century. According to Malthus’s theory, a population grows or declines rapidly as long as the environmental factors for survival are constant, and the rate at which that population changes increases as the population grows. From this theory, Malthus predicted a catastrophic future for humanity. The number of humans was growing much more quickly than the amount of food that could be produced by the world’s farmlands. Eventually, Malthus argued, a point would be reached when the human population would succumb to global famine and decline. Malthus’s bleak vision did not happen, thanks to technological advances in agriculture and the development of artificial fertilizers, but his population model became applicable to species populations within ecosystems. Every habitat, and the niche occupied by a species within its community of organisms, has a carrying capacity—the maximum population that can be supported by the resources available, such as water, space, food, and light. Any rise in population above this level is likely to be reduced by naturally ■ Competitive exclusion occurring factors. As a result, wild populations should in theory be more or less static, fluctuating only around the carrying capacity, assuming the random impacts of catastrophic events are ignored. However, this relative equilibrium did not always match up with observations—as in ❯❯ The food species cannot, therefore, be exterminated by the predatory species, under the conditions to which our equations refer. Alfred J. Lotka РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 48 PREDATOR–PREY EQUATIONS British mathematician and evolutionist D’Ancona’s account of a sudden increase in the population of predatory sea fish. One theory to explain this discrepancy started from the premise that the population of predators is related to the size of the population of their food supply, such as prey species. The relationship suggests that when a lot of food is available, there will be a large predator population. The growing predator population should then begin to reduce the amount of prey, which will in turn lead to a drop in the number of predators. The size of both populations will rise and fall, but the ratio of predators to prey will remain stable. Such a balanced theory was still at odds with species observations. Through mathematical modeling, Volterra was able to show that the average sizes of predator and prey populations do indeed oscillate but the rate at which each population is growing or declining is always changing and almost never matches the changes experienced by the other population. To eliminate variables, Volterra made a series of assumptions: first, that the prey and predator species have species and the predation rate. For example, oscillations in the size of an ant population and that of an anteater are barely noticeable because they reproduce at such different rates. The oscillations in the populations of species that breed at similar rates, such as the Iberian lynx and rabbit, are much more pronounced. Nature’s arms race The predator–prey equations revealed that species are locked together in a never-ending struggle, swinging from near disaster and extinction to times of abundance and fertility. In this biological “arms race,” the evolutionary pressure on the prey species is to escape predation and survive, so as to have more offspring. Meanwhile, the predator is under pressure to have a higher predation rate in order to provide food for more offspring. However, neither species is superior, responding instead to the adaptations of the other. The predator–prey relationship between even-toed hoofed mammals—such Predator–prey population cycles The predator and prey populations rise and fall over time in regular cycles. Although the degree to which they change varies, the cycle follows a broadly similar pattern. KEY Prey Predator POPULATION Mathematics without natural history is sterile, but natural history without mathematics is muddled. John Maynard Smith no reproduction limits and the rate of change in a population is proportional to its size; second, that the prey population—presumed to be a herbivore—is always able to find enough food to survive. Next, they assumed that the prey population is the predators’ only source of nourishment, and that the predators never become full and never stop hunting. Finally, they assumed that environmental conditions, such as weather or natural disasters, had no impact on the process. The effect of the genetic diversity of the predators and prey animals on their ability to survive was not taken into account. When plotted on a graph, the predator population trails the rise and fall of the prey population, and is still rising as the prey population starts to decline. This explained D’Ancona’s observation of the larger proportion of predators after the prey population had been allowed to boom by a reduction in fishing. The relative fluctuations of the populations depends on the relative reproductive rates of the two TIME РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS ECOLOGICAL PROCESSES 49 as antelopes and deer—and mammalian carnivores, like the big cats and wolves, is an example of this evolutionary arms race. The hoofed animals have long legs, extended by walking on the very tips of thickened and fused toe bones. This adaptation allows them to outrun and outjump their predators. In response, big cats— such as lions and tigers—have evolved speed and strength to bring down large, fleet-footed prey in surprise attacks. Wolves have evolved the stamina to run for long distances without stopping. This allows them to work as a team to chase down their prey and kill them when the exhausted prey collapse. While the predator–prey equations offer an insight into the population dynamics of two species, the assumptions they rely on are rarely reflected in real life. Some predators do specialize in killing a single prey species, but other factors in the ecosystem also affect their populations. Other applications The Lotka–Volterra equations have been used to study the dynamics of food chains and food webs in which one species may be a predator of Volterra was interested in a mathematical theory of ‘the survival of the fittest.’ Alexander Weinstein Russian mathematician another species but also the prey species of a third. They have also been used to examine the relationship between host and parasite species, which bears some resemblance to that between prey and predator. Parasites often specialize in one host species— a relationship that should resemble the one described by the Lotka– Volterra equations. However, in practice the process of evolution is thought to interfere with this. A parasite does not usually kill its host (those that do are called parasitoids), but can reduce its fitness. The Red Queen evolutionary theory, proposed in the 1970s by Leigh Van Valen, describes how, The parasitoid wasp lays its eggs in aphids (the smaller, yellow insects shown above). It is called a parasitoid because the wasp’s larvae later eat the aphids as they grow. thanks to beneficial genes, certain individuals in a host population are able to maintain their fitness despite the attacks from parasites. The parasites constantly evolve to exploit these seemingly immune individuals, and therefore the beneficial genes in the host population also change. In this way, evolution is happening all the time, as the parasite and host battle it out—although everything appears to stay the same. ■ РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS 50 EXISTENCE IS DETERMINED BY A SLENDER THREAD OF CIRCUMSTANCES ECOLOGICAL NICHES IN CONTEXT KEY FIGURE Joseph Grinnell (1877–1939) BEFORE 1910 In a paper about beetles, Roswell Hill Johnson, a US biologist, is the first person to use the word “niche” in a biological context. AFTER 1927 British ecologist Charles Elton stresses the importance of an organism’s role as well as its “address” in his definition of an ecological niche in his book Animal Ecology. 1957 In an academic paper called “Concluding Remarks,” British ecologist George Evelyn Hutchinson expands the theory of niches to embrace an organism’s entire environment. 1968 A study by Australian D.R. Klein of the introduction, increase, and die-off of reindeer on St. Matthew Island, Alaska, identifies the destructive niche. A n organism’s niche is a combination of its place and its role in the environment. It encompasses how the organism meets its needs for food and shelter, as well as how it avoids predators, competes with other species, and reproduces. All its interactions with other organisms and the nonliving environment are also part of what makes up its niche. A unique niche is an advantage for any animal or plant because this reduces competition with other species. For ecologists, a full knowledge of an organism’s niche is vital to inform interventions to compensate for the environmental changes caused by habitat destruction and climate change. The pioneer of the niche concept was Joseph Grinnell, a US biologist who studied a bird called the California Thrasher. In 1917, he published his observations, which showed how the bird fed and bred in the underbrush of a scrubby There is constant competition for food and resources; better adapted species outcompete those less suited to the environment. Reducing competition increases the chances of survival. Existence of each species is determined by a slender thread of circumstances. Finding a unique niche is the circumstance that removes competition. РЕЛИЗ ПОДГОТОВИЛА ГРУППА "What's News" VK.COM/WSNWS ECOLOGICAL PROCESSES 51 See also: Competitive exclusion principle 52–53 ■ Field experiments 54–55 ■ Animal ecology 106–113 ■ Niche construction 188–189 An ultra-specialist habitat known as chaparral, and how it escaped predators by running through the underbrush. The thrasher’s camouflage, short wings, and strong legs were perfectly adapted for life in this environment. Grinnell saw the chaparral habitat as the thrasher’s “niche.” His idea also allowed for “ecological equivalence” in plants and animals, whereby species distantly related and living far ap