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