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Evidence of Evolution Environmental Change • Earth’s topography and environment has changed drastically over time – Theory of plate tectonics • Earth is old • Environment is dynamic, species need to be dynamic Evidence for Evolution Lecture 3 Winter 2014 Evidence of Evolution 1 2 Formation of Fossils 3 Fossil Any trace of an organism that lived in the past Fossil Record – Ordered sequence of fossils as they appear in the rock layers 4 Dating Fossils Evidence of Evolution 5 Transitional forms • A fossil species whose traits are intermediate between an older and younger species See Fig 22.20 1 6 7 Transitional Forms Transitional Forms • Tiktaalik roseae Model of Tiktaalik Evidence of Evolution 8 Biogeography • The geographical distribution of species • Extinct species in fossil record were succeeded by similar living species Evidence of Evolution Homologies • Similarities in characteristics due to descent from a common ancestor • Structures are modified to fit new functions Comparisons at many levels • Anatomical (structural) • Developmental • Molecular (Genetic) 9 Evidence of Evolution Vestigial structures • Reduced or incompletely developed structures • No function or reduced function in organism 10 11 Evidence of Evolution • Anatomical (Structural) homologies – Morphological traits that are similar between organisms – Modifications not perfect See Fig. 22.15 2 12 Evidence of Evolution • Developmental homologies 13 • Molecular (Genetic) homologies – When newly developing embryos of different species have a similar trait – Similarity in the DNA/RNA sequences • Closely related organisms have many similar stages of development See Fig. 22.16 Homology vs. Analogy Evidence of Evolution 14 • More closely related organisms will have more similar nucleotide sequences in their DNA Homology vs. Analogy 15 • Homology – Similarity among organisms due to shared ancestry • Analogy – Similarity among organisms due to adaptations to similar environments • Convergent evolution Evidence of Evolution 16 • Evolution is observable within our lifetime – Antibiotic resistant bacteria – Insect resistant to pesticides – Plants resistant to herbicides – Galapagos finches • Evolution can be tested experimentally • Read pgs. 460-462, & Fig. 22.13 & 22.14 (MRSA, soapberry bugs) 3