Evolution: Speciation and More Evidence Evolution is a FACT 1. Key concepts 2. Speciation 3. More evidence 4. Conclusions Outline Key Concepts: A species consist of one or more populations of individuals that can interbreed and produce offspring Speciation is the process by which daughter species evolve from a parent species All species that have ever lived are related Comparative anatomy help reconstruct patterns of change through time Biochemical comparisons also provide evidence of evolution
Speciation The process by which daughter species evolve from a parent species Speciation occurs as results of Natural selection Genetic drift Mutation Move Evidence Various types of evidence help scientists determine evolutionary relationships among organisms 1. The fossil record 2. Fossil dating 3. Comparative anatomy 4. Comparative embryology 5. Molecular biology The fossil record Fossil: any record of a dead organism, frequently preserved in stratified, sedimentary rocks Older strata below, newer strata above, provide relative record of geologic time and of hardbodied organisms alive at that time
Fossil dating Radiocarbon dating method: Depends on ratio of radioactive carbon ( 14 C) to stable, nonradioactive form, 12 C in fossil New 14 C continually formed and added into living cells but stops when organism dies Fossil 14 C decays, so ratio changes in fossil with half-life of ~5000 years Strata of sedimentary rock at the Grand Canyon Descent with modification
Comparative anatomy Evolutionary relationships determined by examining anatomical structures: Homology Similarity in body parts in different organisms Attributable to descent from a common ancestor Analogy Similarity in body parts in different organisms Attributable to similar environmental pressures Homologous Structures Vertebrate forelimbs Comparative anatomy
Comparative embryology Embryonic stages of many organisms similar despite adult differences Suggests relationships among those organisms derived from some common ancestor Similar Vertebrate Embryos Adult shark Aortic arches Two-chambered heart Certain veins Early human embryo Molecular biology Mutation (change) in DNA is basis for evolutionary change Homology in base sequences between two organisms suggests evolutionary relationship More homology, closer relationship; less homology = more mutations so more distant relationship
Comparative Biochemistry Kinds and numbers of biochemical traits that species share is a clue to how closely they are related Can compare DNA, RNA, or proteins More similarity means species are more closely related Comparing Proteins Compare amino acid sequence of proteins produced by the same gene Human cytochrome c (a protein) Identical amino acids in chimpanzee protein Chicken protein differs by 18 amino acids Yeast protein differs by 56 Molecular biology
Constructing evolutionary trees Trees are graphs of relationships among various organisms and groups of organisms Pattern of relationships shown on horizontal axis; time on vertical axis Can estimate rates of evolution among different groups Constructing evolutionary trees
In Conclusion A species consists of individuals in a population or populations Genetic divergence is a buildup of differences in allele frequencies between populations Speciation is the process by which species form a population of a parent species In Conclusion There is extensive evidence of evolution based on similarities and differences in body form, function, behavior, and biochemistry Comparative biochemistry has identified similarities and differences among species