BIOL1003 Study Guide - Final Guide: Thylacine, Archaeopteryx, Comparative Anatomy
2.1 Darwin (1809 – 1882)
• 1846-1854 – after publishing the Beagle findings, Darwin spent 8 years on barnacles, learning
comparative anatomy, homology and classification - this helped establish him as a naturalist
so that he could propose the idea of evolution (controversial).
• 1837 – Darwin thought the Galapagos irds ere arieties of okigirds ut Joh Goulds
expertise helped Darwin identify that they were all finches.
• 1859 - Darwin put forward a plausible mechanism for evolution - Natural Selection.
• Darwin's syllogism - if:
i. There is variation within a population (phenotype, behaviour, genotypes, DNA
sequences and chromosomes); and
ii. Variation is heritable; and
iii. There is a struggle for existence; and
iv. “oe ariats surie/reprodue etter tha others…
v. Then natural selection must occur.
• Darwin used a phylogeny or evolutionary tree to establish common ancestry.
• On his second Voyage on the Beagle (1831-1835), Dari as readig Charles Lells Principles
of Geology and read and considered the idea of gradualism – big changes being built up
graduall, ad gradual eig a stepise proess.
Homology
• Richard Owen (1804-1892) interpreted the fossils of the Beagle expedition.
• Homology – common ancestry between structures or character, eg: organs, genes and
behaviours.
• Characters – are just features or features of structures of an organism/species, eg:
feathers: blue vs. red.
• Homologous characters – characters in different organisms that are similar because they
were inherited from a common ancestor.
• By looking at many homologous characters, scientists can estimate which species are closer
relatives of each other, eg: the Tasmanian tiger is marsupial, like the kangaroo. This
homologous character was used to differentiate its phylogeny from that of the placental
wolf.
• Analogy – similarity attributable to similarity in function.
• Ma of Daris other piees of eidee for eolutio are asiall other eaples of
homology:
o Embryology - embryos show homologous characters not obvious in the adult form.
o Vestiges – homologous characters that are dramatically reduced in form and
function from the original, eg: appendix in humans.
o Atavisms – homologous characters found in ancestral species that only appear
rarely in living species, eg: tails in humans.
o Fossils – using shared homologous characters, we can place fossils on cladograms. In
Daris da, ol a fe isolated fossils ere aailale suggestig ho ajor
transitions happened, eg: gradual origin of birds from dinosaurs – origin of feathers:
Archaeopteryx → modern birds.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
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