Darwin and Evolution

Charles Darwin Son of Robert Darwin, a physician and grandson of Erasmus Darwin, also a physician Was to study medicine, stomach not strong enough Studied Theology, loved natural science

Darwin ’ s Voyage Naturalist on the HMS Beagle Looking for a biblical account of creation Many specimens collected (hares, tortoise, finches) and observations made that contradicted creationism Put his ideas into an essay, but sat on it for 20 years for fear of being discredited as a scientist

Pre - Post Darwinian Views Earth is young Fixity of species Adaptation due to creator variation- imperfections Observations should confirm view Earth is old Species related by descent Adaptation = random variations in environmental conditions Observations used to test hypothesis

Evolution versus Creationism Descent with modification- as descent occurs through time – so does diversity Explains the unity and diversity of life Living things share common characteristics because they are descended from a common ancestor Higher being created the species Fixity of species Each species has ideal structure and function

Mid-18 th century contributions Carolus Linnaeus – taxonomy, scala naturae – ladder of life: simple to complex (humans) Count Buffon – French naturalist, work support DWM Erasmus Darwin – grandfather – physician, naturalist, work eluded to DWM All these men’s work opened the door to the thought of evolution but still supported fixity of species

Late 18 th century contributions Georges Cuvier –  comparative anatomy for classification, founded paleontology  Fixity of species supporter  Tried to explain strata of earth was due to catastrophes/mass extinction

Cont. Jean Baptist LaMarck –  First to believe evolution occurs  Inheritance of Acquired traits – use it or lose it – environment brings about change  Phenotype does not result in genetic changes Giraffe neck length Suntan, muscles…

Darwin ’ s Theory of Evolution Influenced by Charles Lyell’s Principle of Geology  James Hutton – geological changes occur slowly over time, natural process: EARTH IS OLD  Contradicts Cuvier – due to catastrophes

Natural Selection Charles Darwin and Alfred Wallace Idea that those organisms that are best suited to their environment will reproduce and pass on their traits Alfred Russell Wallace – sent Darwin essay on Natural selection before he published his own Variations (mutations) are essential to natural selection process ex. Independent assortment

Natural Selection Thomas Malthus – socio-economist – human population increase faster than food supply: struggle for existence Each generation of organisms have same reproductive potential, but not all will survive to reproduce

Natural selection Fitness – ability to survive and reproduce in its environment relative to others  Usually has most resources  Survival of the fittest  Artificial selection – characteristics are selected for and select organisms to reproduce.

Natural Selection Adaptation – trait that helps organism be better suited for its environment  Flippers – water, wont help on land Natural selection occurs because certain members of a population happen to have a variation (mutation) that allows them to survive and reproduce.

Darwin ’ s Theory of Evolution - Evidence Biogeography – study of range and geographic distribution of life forms on earth  Darwin reasoned related species could be modified based on their environment (ex. Tortoises)  Observed geographical changes 1 st hand and collected fossils to support his theory that species are not fixed, but change over time.

Evidence of Evolution Biochemical evidence  Darwin was not aware of biochemical evidence  Amino acids- cytochrome c (used in electron transport)  DNA/RNA/enzymes – similarities  Introns (junk DNA) Fossils

Evidence of Evolution Anatomical structures  Homologous structures - similar in structure but have different function  Vestigial structures – features that are fully developed in one group of organisms but are reduced and may have no function in similar groups  Embryological development – look at dorsal rod (notochord), pharyngeal slits (gills)…

Theory of Evolution Unifying theory in biology Large number of observations have not yet been found lacking or disproven