Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 22 Descent with Modification: A Darwinian View of Life

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Darwin Introduces a Revolutionary Theory A new era of biology began on November 24, 1859, the day Charles Darwin published On the Origin of Species by Means of Natural Selection The Origin of Species focused biologists’ attention on the great diversity of organisms Video: Galápagos Marine Iguana Video: Galápagos Marine Iguana

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Darwin made two major points in his book: – Many current species are descendants of ancestral species – Natural selection is a mechanism for this evolutionary process

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species To understand why Darwin’s ideas were revolutionary, we must examine them in relation to other Western ideas about Earth and its life

LE 22-2 Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Cuvier (fossils, extinction) Lyell (modern geology) Darwin (evolution, natural selection) Mendel (inheritance) Wallace (evolution, natural selection) French Revolution U.S. Civil War American Revolution 1795Hutton proposes his theory of gradualism. 1798Malthus publishes “Essay on the Principle of Population.” 1809Lamarck publishes his theory of evolution. 1830Lyell publishes Principles of Geology. 1831–1836Darwin travels around the world on HMS Beagle. 1837Darwin begins his notebooks on the origin of species. 1844Darwin writes his essay on the origin of species. 1858Wallace sends his theory to Darwin. 1859The Origin of Species is published Mendel publishes inheritance papers.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Resistance to the Idea of Evolution The Origin of Species – Shook the deepest roots of Western culture – Challenged a worldview that had been prevalent for centuries

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Scale of Nature and Classification of Species The Greek philosopher Aristotle viewed species as fixed and unchanging The Old Testament holds that species were individually designed by God and therefore perfect Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose Linnaeus was a founder of taxonomy, the branch of biology concerned with classifying organisms

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fossils, Cuvier, and Catastrophism The study of fossils helped to lay the groundwork for Darwin’s ideas Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata Video: Grand Canyon Video: Grand Canyon

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Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Theories of Gradualism Gradualism is the idea that profound change can take place through the cumulative effect of slow but continuous processes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Geologists Hutton and Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today This view strongly influenced Darwin’s thinking

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lamarck’s Theory of Evolution Lamarck hypothesized that species evolve through use and disuse and the inheritance of acquired traits The mechanisms he proposed are unsupported by evidence

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Concept 22.2: In The Origin of Species, Darwin proposed that species change through natural selection As the 19th century dawned, it was generally believed that species had remained unchanged since their creation However, a few doubts about the permanence of species were beginning to arise

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Darwin’s Research As a boy and into adulthood, Charles Darwin had a consuming interest in nature After receiving his B.A. degree, he was accepted on board the HMS Beagle, which was embarking on a voyage around the world

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Voyage of the Beagle During his travels on the Beagle, Darwin collected specimens of South American plants and animals He observed adaptations of plants and animals that inhabited many diverse environments His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands near the equator west of South America

LE 22-5 NORTH AMERICA SOUTH AMERICA AFRICA EUROPE AUSTRALIA PACIFIC OCEAN ATLANTIC OCEAN England Cape of Good Hope Cape Horn Tierra del Fuego Galápagos Islands Darwin in 1840, after his return HMS Beagle in port Equator Tasmania New Zealand Andes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Video: Albatross Courtship Ritual Video: Albatross Courtship Ritual Video: Blue-footed Boobies Courtship Ritual Video: Blue-footed Boobies Courtship Ritual Video: Galápagos Island Overview Video: Galápagos Island Overview Video: Galápagos Sea Lion Video: Galápagos Sea Lion Video: Soaring Hawk Video: Soaring Hawk Video: Galápagos Tortoise Video: Galápagos Tortoise

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Darwin’s Focus on Adaptation In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes From studies made years after Darwin’s voyage, biologists have concluded that this is indeed what happened to the Galápagos finches

LE 22-6 Cactus eater. The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp. Seed eater. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground. Insect eater. The green warbler finch (Certhidea olivacea) used its narrow, pointed beak to grasp insects.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s Darwin quickly finished The Origin of Species and published it the next year

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Origin of Species Darwin developed two main ideas: – Evolution explains life’s unity and diversity – Natural selection is a cause of adaptive evolution

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Descent with Modification The phrase descent with modification summarized Darwin’s perception of the unity of life The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past In the Darwinian view, the history of life is like a tree with branches representing life’s diversity

LE 22-7 Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Years ago 0 10, Millions of years ago Moeritherium Barytherium Deinotherium Mammut Platybelodon Stegodon Mammuthus Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Natural Selection and Adaptation Evolutionary biologist Ernst Mayr has dissected the logic of Darwin’s theory into three inferences based on five observations

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Observation #1: For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully

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Observation #2: Populations tend to be stable in size, except for seasonal fluctuations Observation #3: Resources are limited Inference #1: Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Observation #4: Members of a population vary extensively in their characteristics; no two individuals are exactly alike

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Observation #5: Much of this variation is heritable Inference #2: Survival depends in part on inherited traits; individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Inference #3: This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over generations

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Artificial Selection In artificial selection, humans have modified other species over many generations by selecting and breeding individuals with desired traits

LE Cabbage Flower clusters Terminal bud Lateral buds Brussels sprouts Leaves Kale Stem Kohlrabi Wild mustard Broccoli Cauliflower Flowers and stems

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Summary of Natural Selection Natural selection is differential success in reproduction from interaction between individuals that vary in heritable traits and their environment Natural selection produces an increase over time in adaptation of organisms to their environment If an environment changes over time, natural selection may result in adaptation to these new conditions Video: Seahorse Camouflage Video: Seahorse Camouflage

LE A flower mantid in Malaysia A stick mantid in Africa

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 22.3: Darwin’s theory explains a wide range of observations Darwin’s theory of evolution continues to be tested by how effectively it can account for additional observations and experimental outcomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Natural Selection in Action Two examples provide evidence for natural selection: the effect of differential predation on guppy populations and the evolution of drug- resistant HIV

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Differential Predation in Guppy Populations Researchers have observed natural selection leading to adaptive evolution in guppy populations

LE 22-12a Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Experimental transplant of guppies Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools” Pools with killifish but no guppies prior to transplant

LE 22-12b Control population: Guppies from pools with pike-cichlids as predators Experimental population: Guppies transplanted to pools with killifish as predators 92.3 Females Age of guppies at maturity (days) Males Females Mass of guppies at maturity (mg) Males

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Evolution of Drug-Resistant HIV The use of drugs to combat HIV selects for viruses resistant to these drugs The ability of bacteria and viruses to evolve rapidly poses a challenge to our society

LE Patient No. 3 Patient No. 2 Patient No Weeks Percent of HIV resistant to 3TC

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Homology, Biogeography, and the Fossil Record Evolutionary theory provides a cohesive explanation for many kinds of observations

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Homology Homology is similarity resulting from common ancestry

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anatomical Homologies Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor

LE Human Cat Whale Bat

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparative embryology reveals anatomical homologies not visible in adult organisms

LE Chick embryo (LM) Human embryo Pharyngeal pouches Post-anal tail

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vestigial organs are remnants of structures that served important functions in the organism’s ancestors

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Molecular Homologies Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Homologies and the Tree of Life The Darwinian concept of an evolutionary tree of life can explain homologies Anatomical resemblances among species are generally reflected in their molecules, genes, and gene products

LE Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide 100% 95% 87% 69% 54% 14% Rhesus monkey Species Human Mouse Chicken Frog Lamprey

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biogeography Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some similar mammals that have adapted to similar environments have evolved independently from different ancestors

LE Sugar glider Flying squirrel NORTH AMERICA AUSTRALIA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Fossil Record The succession of forms observed in the fossil record is consistent with other inferences about the major branches of descent in the tree of life

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record Paleontologists have discovered fossils of many such transitional forms

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What Is Theoretical about the Darwinian View of Life? In science, a theory accounts for many observations and data and attempts to explain and integrate a great variety of phenomena Darwin’s theory of evolution by natural selection integrates diverse areas of biological study and stimulates many new research questions