darwin and evolution
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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
1831 - 1836 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-18th 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 18th 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 1st 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
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