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Patterns of Evolution


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Homology, embryology, fossil record, phylogeny

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Patterns of Evolution

  1. 1. Life Science Patterns of Evolution Changes Over Time
  2. 2. In your lab notebook, please answer as best you can: Week 13 Review Quiz Bonus: What is the geologic column? - a sequence of rock layers that combines all the known fossils and rock formations on Earth arranged from oldest to youngest 1. Name two factors that increase an organism’s chance of fossilization. • Hard parts (shell/bone), quick burial (slows decomposition), location of death (dry/cold vs. harsh or warm/wet) 1. When all members of a certain species die, they are said to be… • Extinct 1. Are fossil molds & casts found in ice, tar, sedimentary rock, or amber? • Rock 1. An opinion that prevents the objective analysis of a set of facts is a… • Bias 1. What is dendrochronology? • Tree-ring dating (the technique of dating rock layers and fossils by cross- dating the patterns of annual growth rings in tree trunks)
  3. 3. What is Evolution? • Simple: "change over time“ • Biological Evolution: "descent with modification" – many, many, MANY small changes over LOOOOOOOOONG periods of time that result in the formation of many DIFFERENT types of organisms
  4. 4. Types of Evolution • Microevolution – Small changes within a species' set of genes that result in phenotypic differences – Decades or centuries (short time) – Under certain environmental conditions, can produce new, closely-related species • Macroevolution – descent with modification – the process by which modern organisms have descended from ancient ancestors due to many small changes over millions of years (long time)
  5. 5. Speciation • A lineage-splitting event that produces a new, separate species is called speciation – reproduced in lab experiments – populations change so much that they no longer can interbreed and exchange genes – requires geographic isolation • Macroevolution = speciation on a grand scale • Individuals DO NOT evolve over time, but POPULATIONS do!
  6. 6. Week 13 Lab Paper Airplane AdaptationsObservation -A mutation is a change in the nucleotide base sequence of a gene (in a cell’s DNA) that results in the manufacture of altered proteins which determine an inherited trait. -Mutations are rarely beneficial and only passed to offspring if they occur in germ cells or gametes. -Adaptations are traits caused by mutations that increase an organism’s or population’s survival and/or ability to reproduce. -Evolutionary fitness describes a population’s ability to survive and reproduce in its current environment. -Natural selection describes how a more fit population may be “chosen” by their environment to survive. (This is really an awkward way of saying that a less fit population that lacks adaptations will probably not survive or pass on their genes.) -Biological evolution occurs over long periods of time within populations of living things due to differences in the frequency and combination of genes that determine or influence inherited traits.
  7. 7. Paper Airplane Adaptations - For this activity, paper airplanes will represent organisms of the same species. Paper clips will represent food, which the organisms will be competing for by trying to reach the box. Certain airplane designs may provide an advantage for the “organism” to reach the food sooner and stay alive. If your airplane is the last to reach the box in the center of the circle, your organism will die and you will have to sit out for the rest of the game!
  8. 8. The Geologic Column • Assembled from different strata from around the world with a bias towards evolution • Assumes sedimentation occurs evenly and slowly over millions of years “the present is key to the past” • Large gaps remain in the fossil record – they may be still hidden, have been destroyed, or never existed • Out of place fossils & lack of transitional fossils is puzzling
  9. 9. The "Cambrian Explosion" • Evidence in the fossil record shows that all major phylla were established in the transition from Late Precambiran to Early Cambrian time • In the creationist model, these animals represent descendants of original created kinds that became extinct during the Flood of Genesis. • Gradual evolution struggles to account for the sudden appearance of so many types of life at one time. – "Punctuated Equilibrium" is one solution • It is puzzling why there are little to no "precursor" fossils to all these varieties of life.
  10. 10. Homologous Features • A structure found in different species, but derived from a common ancestral structure. – The structure may or may not be used for the same function in the species in which it occurs. Examples: • skeletal structure of vertebrate limbs • embryonic similarities • similarities in DNA, RNA, & the proteins the code for
  11. 11. Embryologic Development • Structures that have different mature forms but develop from the same embryonic tissues • Limbs are structurally similar but have different functions • Recent developments in biochemistry show "similarity does not imply a genetic relationship" Alligator Turtle Primitive Fish Mammal
  12. 12. Comparative Embryology
  13. 13. Common Ancestors?
  14. 14. Inherited Traits • Neo-Darwinism sites the similarities of genetics between species as evidence of evolution • Other scientists look DNA and see the complexity and efficiency of information transfer as evidence for a single, intelligent “designer”
  15. 15. Phylogeny • The evolutionary history of a species • Relationship to other species is based on : – Fossil record – Morphology (similar physical structures) – Embryological patterns of development – Genetic similarities (DNA)
  16. 16. Cladograms • A cladogram is based on sorting similar organisms into groups called clades that prioritize evolutionary relationships (phylogeny) over traditional shared characteristics (Linnaean classification) • Cladistics is a relatively new system of grouping that identifies similar derived characteristics to represent evolutionary relationships. • Organisms on the same “branch” descended from a common ancestor • The branching pattern identifies speciation events (splits in two where changes occur) • Relies most heavily on genetic similarities (DNA)
  17. 17. Six Kingdoms • Archaebacteria • Eubacteria • Protists • Fungi • Plants • Animals • This phylogenetic tree is VERY simplified! • First true cells are thought to have arisen from aquatic, anaerobic, "protocells" 6 EUBACTERIA ARCHAEBACTERIA