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Unformatted text preview: on observational evidence from fossils, geology, comparative anatomy, & nature. • His mechanism for change natural selection, based on observations of natural populations: Those with heritable traits that better suit them to their environment – are more likely to survive & reproduce – these traits are selected for • Darwin reasoned that natural selection, acting over long periods of time, could lead to formation of descendant species. • Unlike Darwin, we know that the source of, and inheritance of genetic variation arises from variability in DNA. – Mutations, random changes in DNA, provide the raw material for evolutionary change. On occasion, mutationsprovide a benefit. – Adaptations may arise from such beneficial mutations; these are features that aid an organisms survival and/or reproductive success in its’ environment. • Variations on a theme: similar bone structure of limbs (can infer a common ancestry); yet are adaptations for different functions. • Darwin’s view of life – descent with modification – is depicted in evolutionary “trees”. Such trees represent evolutionary histories among organisms. Tree branches Tips of the branches Tree root Modified descendants • The diversity of life on Earth is categorized into groups based on similarities of several features. (taxonomy) • The groupings vary in size from 1 (species level) to broader, more inclusive, groups, ending with domain. Biological Classification of Life • Grouping the diversity of life based on similarities of features. • Taxonomy: orders species into increasingly larger groups. • Species (smallest) Species Domain (largest). • Such nested groupings often reflect related among members. The Domains & Kingdoms of Life Life on Earth Prokaryotes Domain Bacteria Kingdom Bacteria Domain Archaea Kingdom Archaebacteria...
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