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Evolutionary Trees in the Ecological Garden Pre-Darwin thoughts Life arose by special creation • Organisms were formed as we find them today – That is species do not change • Creation as a recent event – In 1664 Archbishop James Ushher calculated that the earth was 5668 years old – 26th of October, 4004 B.C., 9 AM A comparison • Species created independently • Species do not change through time • Created recently • Process is creation (God did it) • Species are related to one another • Species change over time • Life on earth is ancient • Process: descent with modification’, by way of natural selection Darin was not the first to question the Biblical scheme • Charles Lyell (geologist) accepted the concept of extinctions, and that not all species were created at the same time • He proposed a “natural” process of extinction – but creation remained a mystery • Darwin proposed natural (“materialistic”) processes for both creation of new species, and extinction The Larckian System • A linear progressive evolution – a species changed over time. • There were many starting points. • Species did not go “extinct” they became more complex life forms • Based on transmittance of characteristics by use and disuse The Tree concept • The evolutionary relationships among groups of organisms – Reflects single unique history of life • When new species evolve from existing species – the event is called speciation Speciation How to make a tree • Principle of parsimony – Less complicated explanations more likely to be correct – In evolutionary biology, phylogenies that require fewer evolutionary transitions more likely to be correct Which would you pick? Parsimony determines the best answer Applying cladistic methods A clade is a grouping that includes a common ancestor and all the descendents (living and extinct) of that ancestor. • Identify synapomorphic traits based on • Structural, • Developmental similarities • Genetic comparisions • Use parsimony to infer phylogenetic relationships • Validating and assessing tree Building Evolutionary Trees • Chose the taxa • Determine the characteristics • Identify a probable order of evolution for each character • Group organisms by changed characteristics (synamorphy) • Check for parsimony • Remember – each tree is a theory & may be changed to meet challenges of new discoveries • reference Biological classification is a reflection of evolutionary history • Why is this so? • Descendants of common ancestors differentiate from one another • Fossils provide a glimpse of the process – and information about the timeline What are the evolutionary transitions? Modern evolutionary trees • Species can split or merge, some species die out Synamorphy • A derived or changed character. That can be used as indicators of common ancestry. – Consider a ancestor of a beetle clade had five antennal segments and passed that character state onto its immediate descendents – one lineage within the clade evolved six antennal segments Bird evolution: and Example of use of Synamorphy Example: the evolutionary relationships of whales Three dominions • Bacteria • Eucarya • Archaea • Reference 1 • Reference 2 Archaea Like th Eukarya they have Histones and Introns Histones: Act as spools around which DNA winds and they play a role in gene regulation. Introns are sections of DNA that will be spliced out after transcription, but before the RNA is used. Evolution of Eukaryotic life Lack the histones and introns, of Archaea and Prokaryots. Parasexual transfer of genetic information Conjugation, transduction and transformation Evolution of Bacteria Exploring the tree of life • Remember – every phylogeny is a hypothesis and is subject to debate and revision. • Link to tree of Life • Modern View is of a Tree – Not a Ladder – Eukaryotes Tree The “ladder of life” as per Aristotle Developmental patterns • Why are embryos less differentiated than adults? • Is this true for insects? • Parallel patterns in evolution: Support for evolution directed by natural selection A phylogeny is a hypothesis What data might test these hypotheses? • Morphology, including fossils • DNA sequences