Descent with Modification: A Darwinian View of Life

1. CHAPTER 22 DESCENT WITH MODIFICATION: A DARWINIAN VIEW OF LIFE

2. GENESIS 1 • THE CREATION OF THE WORLD • 1:1 IN THE BEGINNING1 GOD2 CREATED3 THE HEAVENS AND THE EARTH.4 • 1:2 NOW5 THE EARTH6 WAS WITHOUT SHAPE AND EMPTY,7 AND DARKNESS8 WAS OVER THE SURFACE OF THE WATERY DEEP,9 BUT THE SPIRIT OF GOD10 WAS MOVING11 OVER THE SURFACE12 OF THE WATER.13 1:3 GOD SAID,14 “LET THERE BE15 LIGHT.”16 AND THERE WAS LIGHT! 1:4 GOD SAW17 THAT THE LIGHT WAS GOOD,18 SO GOD SEPARATED19 THE LIGHT FROM THE DARKNESS. 1:5 GOD CALLED20 THE LIGHT “DAY” AND THE DARKNESS21 “NIGHT.” THERE WAS EVENING, AND THERE WAS MORNING, MARKING THE FIRST DAY.22

3. I. HISTORICAL CONTEXT FOR EVOLUTIONARY THEORY • WESTERN CULTURE RESISTED EVOLUTIONARY VIEWS OF LIFE • DARWIN'S THEORY THAT NATURAL SELECTION IS RESPONSIBLE FOR EVOLUTIONARY CHANGE WAS A RADICAL DEPARTURE FROM THE DOMINANT RELIGIOUS AND PHILOSOPHICAL CLIMATE OF THE NINETEENTH-CENTURY WESTERN WORLDVIEW. B. THEORIES OF GEOLOGICAL GRADUALISM HELPED CLEAR THE PATH FOR EVOLUTIONARY BIOLOGISTS • GEOLOGISTS HUTTON AND LYELL PERCEIVED THAT CHANGES IN EARTH’S SURFACE CAN RESULT FROM SLOW, CONTINUOUS ACTIONS. C. LAMARCK PLACED FOSSILS IN AN EVOLUTIONARY CONTEXT • LAMARCK HELPED PAVE THE WAY FOR DARWIN BY EMPHASIZING THE INTERACTIONS BETWEEN ORGANISMS AND THEIR ENVIRONMENT.

5. II. THE DARWINIAN REVOLUTION • FIELD RESEARCH HELPED DARWIN FRAME HIS VIEW OF LIFE: SCIENCE AS A PROCESS • DARWIN'S EXPERIENCES ON THE VOYAGE OF HMS BEAGLE PROVIDED MUCH OF THE BACKGROUND FOR HIS THEORY THAT NEW SPECIES ORIGINATE FROM ANCESTRAL FORMS BY THE GRADUAL ACCUMULATION OF ADAPTATIONS. • DARWIN AND ALFRED WALLACE INDEPENDENTLY ARRIVED AT THE THEORY THAT NATURAL SELECTION IS THE MECHANISM OF EVOLUTIONARY CHANGE.

7. B. THE ORIGIN OF SPECIES DEVELOPED 2 MAIN POINTS: EVOLUTION AND NATURAL SELECTION AS ITS MECHANISM • NATURAL SELECTION IS BASED ON DIFFERENTIAL SUCCESS IN REPRODUCTION, MADE POSSIBLE BECAUSE OF HERITABLE VARIATION AMONG THE INDIVIDUALS OF ANY POPULATION AND THE TENDENCY FOR A POPULATION TO PRODUCE MANY MORE OFFSPRING THAN THE ENVIRONMENT CAN SUPPORT. • PRINCIPLES: • POPULATIONS PRODUCE MORE INDIVIDUALS THAT CAN POSSIBLY SURVIVE • POPULATION SIZES REMAIN STABLE • RESOURCES ARE LIMITED • ‘HERITABLE” VARIATION EXISTS AMONG ORGANISMS • INDIVIDUALS COMPETE FOR SURVIVAL • “SURVIVAL OF THE FITTEST”

8. FIGURE: 22.7 NATURAL SELECTION IN ACTION: BEAK EVOLUTION IN ONE OF DARWIN’S FINCHES

9. III. EVIDENCE OF EVOLUTION • EVIDENCE OF EVOLUTION PERVADES BIOLOGY • EVOLUTION IS VALIDATED BY EVIDENCE FROM THE FOSSIL RECORD AND FROM MANY FIELDS OF BIOLOGY, INCLUDING BIOGEOGRAPHY, COMPARATIVE ANATOMY, COMPARATIVE EMBRYOLOGY, AND MOLECULAR BIOLOGY.

10. 22.8 TRANSITIONAL FOSSILS LINKING PAST AND PRESENT

11. 22.9 HOMOLOGOUS STRUCTURES

12. VESTIGIAL STRUCTURES

13. VESTIGIAL STRUCTURES: have no apparent function, but resemble structures their presumed ancestors • Some Vestigial Traits in Humans • Ear-wiggling muscles Three small muscles around each ear that are large and important in some mammals, such as dogs, turning the ears toward a source of sound. Few people can wiggle their ears, and none can turn them toward sound. • Tail Present in human and all vertebrate embryos. In humans, the tail is reduced; most adults only have three to five tiny tail bones and, occasionally, a trace of a tail-extending muscle. • Appendix Structure which presumably had a digestive function in some of our ancestors, like the cecum of some herbivores. In humans, it varies in length from 5–15 cm, and some people are born without one. • Wisdom teeth Molars that are often useless and sometimes even trapped in the jawbone. Some people never develop wisdom teeth.

16. Ontogeny Recapitulates Phylogeny • ONTOGENY: STAGES IN DEVELOPMENT • PHYLOGENY: EVOLUTIONARY RELATIONSHIPS

17. 22.11 MOLECULAR DATA AND THE EVOLUTIONARY RELATIONSHIPS OF VERTEBRATES

18. B. WHAT IS THEORETICAL ABOUT THE DARWINIAN VIEW OF LIFE? • DARWIN'S THEORY OF NATURAL SELECTION UNIFIED BIOLOGY AND PLACED IT IN THE REALM OF SCIENCE.