Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Chapter 22 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 (Species: a group whose members possess similar anatomical characteristics and have the ability to interbreed, and produce viable offspring)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Origin of Species Focused biologists’ attention on the great diversity of organisms Figure 22.1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Darwin made two major points in his book – He presented evidence that the many species of organisms presently inhabiting the Earth are descendants of ancestral species – He proposed a mechanism for the evolutionary process, natural selection

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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The historical context of Darwin’s life and ideas Figure 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) 1750 American RevolutionFrench Revolution U.S. Civil War Hutton proposes his theory of gradualism Malthus publishes “Essay on the Principle of Population.” 1809 Lamarck publishes his theory of evolution Lyell publishes Principles of Geology. 1831–1836 Darwin travels around the world on HMS Beagle. Darwin begins his notebooks on the origin of species Darwin writes his essay on the origin of species Wallace sends his theory to Darwin The Origin of Species is published Mendel publishes inheritance papers. 1865

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 of the Bible – Holds that species were individually designed by God and therefore perfect

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carolus Linnaeus Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose Was a founder of taxonomy, classifying life’s diversity “for the greater glory of God”

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 Figure 22.3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Paleontology, the study of fossils – Was largely developed by French scientist Georges Cuvier Cuvier opposed the idea of gradual evolutionary change – And instead 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 Exerted a strong influence on 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 – But the mechanisms he proposed are unsupported by evidence Figure 22.4

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 22.2: Darwin and Natural Selection As a boy and into adulthood, Charles Darwin – Had a consuming interest in nature Soon after Darwin received his B.A. degree – He was accepted on board the HMS Beagle, which was about to embark 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 observed and collected many specimens of South American plants and animals Darwin observed various adaptations of plants and animals – That inhabited many diverse environments

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Darwin’s interest in the geographic distribution of species – Was kindled by the Beagle’s stop at the Galápagos Islands near the equator west of South America Figure 22.5 England EUROPE NORTH AMERICA Galápagos Islands Darwin in 1840, after his return SOUTH AMERICA Cape of Good Hope Cape Horn Tierra del Fuego AFRICA HMS Beagle in port AUSTRALIA Tasmania New Zealand PACIFIC OCEAN Andes ATLANTIC OCEAN

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Darwin’s Focus on Adaptation As Darwin reassessed all that he had observed during the voyage of the Beagle – He began to perceive adaptation to the environment and the origin of new species as closely related processes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings From studies made years after Darwin’s voyage – Biologists have concluded that this is indeed what happened to the Galápagos finches Figure 22.6a–c (a) Cactus eater. The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp. (c) Seed eater. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground. (b) Insect eater. The green warbler finch (Certhidea olivacea) uses its narrow, pointed beak to grasp insects.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In 1844, Darwin wrote a long essay on the origin of species and natural selection – But he was reluctant to introduce his theory publicly, anticipating the uproar it would cause In June 1858 Darwin received a manuscript from Alfred Russell Wallace – Who had independently 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 – States that all organisms are related through descent from an ancestor that lived in the remote past

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In the Darwinian view, the history of life is like a tree with multiple branchings from a common trunk to the tips of the youngest twigs, that represent the diversity of living organisms Figure 22.7 Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Years ago Millions of years ago Deinotherium Mammut Stegodon Mammuthus Platybelodon Barytherium Moeritherium Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Artificial Selection In the process of artificial selection – Humans have modified other species over many generations by selecting and breeding individuals that possess desired traits Figure Terminal bud Lateral buds Brussels sprouts Cabbage Flower cluster Leaves Cauliflower Flower and stems Broccoli Wild mustard Kohlrabi Stem Kale

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Summary of Natural Selection Natural selection is differential success in reproduction – That results from the interaction between individuals that vary in heritable traits and their environment

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Natural selection can increase the adaptation of organisms to their environment, over time Figure (a)A flower mantid in Malaysia (b)A stick mantid in Africa

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings If an environment changes over time – Natural selection may result in adaptation to these new conditions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 22.3: Natural Selection in Action – Two examples provide evidence for natural selection

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 Reznick and Endler transplanted guppies from pike-cichlid pools to killifish pools and measured the average age and size of guppies at maturity over an 11-year period (30 to 60 generations). EXPERIMENT Pools with killifish, but not guppies prior to transplant Experimental transplant of guppies Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools” Figure 22.12

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings RESULTS After 11 years, the average size and age at maturity of guppies in the transplanted populations increased compared to those of guppies in control populations Weight of guppies at maturity (mg) Age of guppies at maturity (days) Control Population: Guppies from pools with pike-cichlids as predators Experimental Population: Guppies transplanted to pools with killifish as predators 76.1 Males Females Males Females CONCLUSION Reznick and Endler concluded that the change in predator resulted in different variations in the population (larger size and faster maturation) being favored. Over a relatively short time, this altered selection pressure resulted in an observable evolutionary change in the experimental population.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Evolution of Drug-Resistant HIV In humans, the use of drugs selects for pathogens that through chance mutations are resistant to the drugs’ effects Natural selection is a cause of adaptive evolution

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Researchers have developed numerous drugs to combat HIV – But using these medications selects for viruses resistant to the drugs Figure Patient No. 1 Patient No. 2 Patient No. 3 Percent of HIV resistant to 3TC Weeks

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 – Is similarity resulting from common ancestry

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anatomical Homologies Homologous structures between organisms – Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor Figure HumanCat Whale Bat

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparative embryology – Reveals additional anatomical homologies not visible in adult organisms Figure Pharyngeal pouches Post-anal tail Chick embryo Human embryo

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 Biologists also observe homologies among organisms at the molecular level – Such as genes that are shared among organisms inherited from a common ancestor

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anatomical resemblances among species – Are generally reflected in their molecules, their genes, and their gene products Figure Species Human Rhesus monkey Mouse Chicken Frog Lamprey 14% 54% 69% 87% 95% 100% Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide

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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sugar glider AUSTRALIA NORTH AMERICA Flying squirrel Figure Some similar mammals that have adapted to similar environments have evolved independently from different ancestors

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 Figure 22.18