Chapter 22

Darwin’s origin of species challenged long-standing Western ideas, especially those of the Christian church Earth only a few thousand years old unchanging forms of life made individually during single week by Creator

Chapter 22 Plato (427 – 347 BC) 2 worlds : (1) ideal & eternal real world (2) world of imperfection that we perceive through our senses thought evolution would be counter- productive in world already populated by perfect species

Aristotle ( BC) all living things arranged on scale of increasing complexity each form had rung on ladder, with every rung filled species are permanent and perfect

natural theology dedicated to discovering Creator’s plan by studying nature adaptations seen as evidence that the Creator designed each and every species for a particular purpose

Linnaeus sought to discover order in the diversity of life “for the greater glory of God” specialized in taxonomy (developed binomial nomenclature) clustering of species implied no evolutionary kinship

fossils (sedimentary rocks) layers show that a succession of organisms has populated Earth throughout time

paleontology developed by Cuvier documented succession of fossils in Paris Basin advocated catastrophism : each boundary corresponded with a catastrophe of some kind (flood, drought, etc.)

Hutton explain current landforms by looking at mechanisms currently operating in the world (Ex. canyons formed by river) gradualism : profound change is cumulative product of slow, but continuous change

Lyell incorporated Hutton’s ideas into uniformitarianism geologic processes have not changed throughout the history of the Earth

Lamarck oversaw invertebrate collection at Natural History Museum of Paris could see lines of descent when comparing current species with fossils

Lamarck’s ideas use & disuse Ex. blacksmith hammering, giraffe stretching inheritance of acquired characteristics changes during lifetime could be acquired by offspring

Darwin—HMS Beagle goal was to chart unknown S. American coastline Darwin observed adaptations of plants and animals many characteristics were distinct from those of Europe

Darwin—Galapagos species found nowhere else in the world read Lyell’s “Principles of Geology” began to believe that the Earth was very old and constantly changing considered link between origin of new species and adaptation to environment (Ex. finches)

Darwin—theories saw evolution as an explanation for life’s unity and diversity developed concept of natural selection to explain adaptive radiation

Galapagos finches

Darwin—Natural Selection and Adaptation 1. natural selection is differential success in reproduction 2. natural selection occurs through an interaction between the environment and the variability inherent among the individual organisms making up a population 3. the product of natural selection is the adaptation of populations of organisms to their environment

Natural Selection —related ideas Malthus essay on human population connection between natural selection (struggle for existence) and capacity of organisms to “overproduce” --many eggs laid, young born, and seeds spread, but few leave offspring (potential offspring are eaten, freeze, starve, diseased, etc.)

Natural Selection —related ideas in each generation, environmental factors filter heritable variations favoring some over others --differential reproduction results in favored traits being disproportionately represented in the next generation

Natural Selection —related ideas power of selection seen in artificial selection ( breeding ) --Darwin thought the same process could be just as powerful over 100s and 1000s of generations --slight advantages accumulate over generations (gradualism)

Natural Selection —SUMMARY 1. diverse forms of life have arisen by descent with modification from ancestral species 2. mechanism of modification has been natural selection (working over tremendous time periods)

population group of interbreeding individuals belonging to a particular species and sharing a common geographic area --individuals do not evolve --evolution can only be measured in populations

population--examples insecticide-resistant insects --initial use  kills 99% of insects --subsequent sprayings are less effective --natural selection is cause HIV strains resistant to medication (these cases are rapid enough to be observed in short period of time…)

evidence of evolution HOMOLOGY --similar characteristic resulting from common ancestry * anatomical (a) mammal forelimb (b) remodeling / retrofitting (c) vestigial organs * embryological : Ex. pharyngeal pouch * molecular : Ex. DNA & RNA codes

evidence of evolution HOMOLOGY --form a layered pattern, with all life sharing the deepest layer and each smaller group adding fresh homologies to those they share with larger groups --tools of molecular biology have corroborated evolutionary trees (Ex. Amino acid sequences of hemoglobin)

evidence of evolution BIOGEOGRAPHY --geographic distribution of species --species tend to be more closely related to other species from the same area than to other species with the same way of life, but living in different areas --islands provide models for this idea

evidence of evolution FOSSIL RECORD --oldest known species are prokaryotes (supports chemistry, molecular, and cell biology evidence) --chronology: Ex. Fossil fish predate all other vertebrates --transitions: signs of change should be seen in fossil record (Ex. changes in shape of human skull)