Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ch. 22 Descent with Modification

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 The Origin of Species – challenged traditional views of a young Earth inhabited by unchanging 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 Darwin – said many species of organisms are descendants of ancestral species – proposed natural selection as a mechanism for evolution

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, nutural 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 The Scale of Nature and Classification of Species The Greek philosopher Aristotle ( BC) – viewed species as fixed and unchanging – said life forms could be arranged according to increasing complexity The Old Testament of the Bible – states that species were individually designed by God

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carolus Linnaeus ( ) – Grouped similar species into increasingly general categories reflecting what he considered the pattern of their creation a founder of taxonomy - the branch of biology dedicated to the naming and classifying of organisms Developed binomial nomenclature – a two-part naming system that includes the organism’s genus and species

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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Georges Cuvier ( ) – Developed paleontology, the study of fossils – opposed the idea of gradual evolutionary change – advocated catastrophism says that events in the past occurred suddenly and by different mechanisms than those occurring today This explained boundaries between strata and the location of different species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Theories of Gradualism Gradualism – 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 ( ) – Developed the principle of uniformitarianism, the idea that the geologic processes that have shaped the planet have not changed over the course of earth’s history Importance: The earth must be very old. – 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 – parts of the body that are used extensively become larger and larger while those not used deteriorate. – Acquired characteristics are inherited.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparison of Lamarck and Darwin LamarckDarwin Use and disuseVariation Transmission of Acquired characteristics Inheritance Increasing complexityDifferential survival No extinctionextinction Lamarck recognized that species evolve but his explanation of how evolution occurs was flawed.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Darwin’s Research Charles Darwin – Had a strong interest in nature – After receiving 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 – collected many specimens of South American plants and animals – observed adaptations of plants and animals i n many diverse environments

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Beagle’s stop at the Galápagos Islands near the equator west of South America sparked Darwin’s interest in the geographic distribution of species. 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 During and after the voyage of the Beagle, – Darwin began to see a link between adaptation to different environments and the origin of new species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings From studies made years after Darwin’s voyage, biologists concluded that this is 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 1844: Darwin wrote an essay on the origin of species and natural selection – reluctant to introduce his theory publicly, anticipating the uproar it would cause 1858: Darwin received a manuscript from Alfred Russell Wallace who had developed a theory of natural selection similar to Darwin’s 1859: Darwin quickly finished The Origin of Species And published it the next year

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 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 Natural Selection Adaptations – Heritable characteristics that enhance organisms’ ability to survive and reproduce in specific environments. Desert fox: large ears radiate heat. Arctic fox: small ears conserve heat.

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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overproduction Production of more individuals than the environment can support Leads to a competition for resources

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Variations in traits occur Members of a population vary extensively in their characteristics. No two individuals are exactly alike Figure 22.9

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survival depends on inherited traits and the resources available in the environment. Individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals This leads to a gradual change in a population, with favorable characteristics accumulating over generations

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Summary of Natural Selection Natural selection is differential success in reproduction – 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 produce an increase over time i n the adaptation of organisms to their environment.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Artificial Selection – Humans have modified 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 Artificial Selection - breeding

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings If an environment changes over time – Natural selection may result in populations adapting to these new conditions. Populations adapt NOT individual organisms.

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 The ability of bacteria and viruses to evolve rapidly – Poses a challenge to our society

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 – variations on a structure that was present in a common ancestor Figure HumanCat Whale Bat

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparative embryology – Reveals 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 remnants of structures that served important functions in the organism’s ancestors

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Molecular Homologies Biologists can 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 Homologies and the Tree of Life The Darwinian concept of an evolutionary tree of life – Can explain the homologies that researchers have observed

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 FHzf4xnWw atch?v=cHa8jrxdF_4

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Fossil Record The Darwinian view of life – Predicts that evolutionary transitions should be found in the fossil record Paleontologists have discovered fossils of many such transitional forms.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Theory of Evolution In science, a theory – Accounts for many observations and data and attempts to explain and integrate a great variety of phenomena

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Darwin’s theory of evolution by natural selection – Integrates diverse areas of biological study and stimulates many new research questions