Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Evolutionary Classification
Document related concepts
Transcript
18-2 Modern Evolutionary Classification Slide 1 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Evolutionary Classification Linnaeus grouped species into larger taxa mainly according to visible similarities and differences. How are evolutionary relationships important in classification? Slide 2 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Evolutionary Classification Biologists currently group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities. The strategy of grouping organisms is based on evolutionary history and is called evolutionary classification. Slide 3 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Evolutionary Classification Evolutionary Classification • Phylogeny is the study of evolutionary relationships among organisms. • The higher the level of the taxon, the further back in time is the common ancestor of all the organisms in the taxon. • Organisms that appear very similar may not share a recent common ancestor. Slide 4 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Evolutionary Classification Superficial similarities once led barnacles and limpets to be grouped together. Appendages Crab Conical Shells Barnacle Limpet Slide 5 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Evolutionary Classification However, barnacles and crabs share an evolutionary ancestor that is more recent than the ancestor that barnacles and limpets share. Barnacles and crabs are classified as crustaceans, and limpets are mollusks. Slide 6 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Evolutionary Classification Different Methods of Classification Appendages Crab Barnacle Mollusk Crustaceans Conical Shells Limpet Crab Barnacle Molted external skeleton Segmentation CLASSIFICATION BASED ON VISIBLE SIMILARITY Limpet Tiny freeswimming larva CLADOGRAM Slide 7 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Similarities in DNA and RNA Similarities in DNA and RNA How can DNA and RNA help scientists determine evolutionary relationships? The genes of many organisms show important similarities at the molecular level. Similarities in DNA can be used to help determine classification and evolutionary Slide 8 of 24 relationships. Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Similarities in DNA and RNA DNA Evidence DNA evidence shows evolutionary relationships of species. The more similar the DNA of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms. The more two species have diverged from each other, the less similar their DNA will be. Slide 9 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Molecular Clocks Molecular Clocks Comparisons of DNA are used to mark the passage of evolutionary time. A molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently. Slide 10 of 24 Copyright Pearson Prentice Hall End Show 18-2 Modern Evolutionary Classification Molecular Clocks A gene in an ancestral species Molecular Clock 2 mutations new mutation Species A 2 mutations new new mutation mutation Species B Copyright Pearson Prentice Hall Species C Slide 11 of 24 End Show 18-2 Modern Evolutionary Classification Molecular Clocks A molecular clock relies on mutations to mark time. Simple mutations in DNA structure occur often. Neutral mutations accumulate in different species at about the same rate. Comparing sequences in two species shows how dissimilar the genes are, and shows when they shared a common ancestor. Slide 12 of 24 Copyright Pearson Prentice Hall End Show Answer These 1. The strategy of grouping organisms based on evolutionary history is called 1. Evolutionary Classification 2. Phylogeny 2. The study of evolutionary relationships among organisms is called 1. Evolutionary Classification 2. Phylogeny 3. A correct way to determine evolutionary relationships is with 1. Physical Descriptions 2. Molecular Clock 4. Which had the more recent common ancestor? 1. Two species with 78% similarity in DNA 2. Two species with 56% similarity in DNA
