Homologous Structures & Evolution: Shared Bones & Amino Acids, Cheat Sheet of Biology

Download Homologous Structures & Evolution: Shared Bones & Amino Acids and more Cheat Sheet Biology in PDF only on Docsity! Evidence for Evolution Homologous Structures Homologous Structures 1. What are homologous structures? Structures shared by organisms because they descended from a common ancestor. The structures are built from the same bones, but can be modified in form and function. 2. Place the same letter or number on the corresponding bones in each of the front limbs pictured below. 3. Based on the limbs above, what can you conclude about the ancestor shared by the organisms above? The common ancestor to these organisms had the same bones 4. Compare and contrast two limbs from questions 2. Your answer should include an analysis of size, shape, and function. The human and whale front limbs have the same bones in the same positions. The human limb is used for grasping and its bones are longer and thin. The whale limb is used for steering and its bones are shorter and wider. 5. How are the pictured limb structures used to support the theory of evolution? The ancestor to these organisms had the same bones, but the limbs have been modified in form and function (descent with modification). 6. Find a definition for a vestigial structure. Identify 1 structure that scientists classify as vestigial that wasn’t presented in the notes. Structures without a clear or current use in an organisms, but had a use in the ancestor. EX: Sexual organs of dandelions Activity 2. Evidence of Evolution Homologous Structures – Use your notes, book and the Internet to answer the following questions on homologous structures. Amino Acid Sequence and Evolutionary Relationships The biochemical similarity of organisms is another technique used to determine evolutionary relationships between organisms. Though molds, aardvarks, and humans appear to have little in common physically, a study of their proteins reveals certain similarities. Biologists have perfected techniques for determining the sequence of amino acids in proteins. By comparing the amino acid sequences in homologous proteins of similar organisms and of diverse organisms, evolutionary relationships that might otherwise go undetected can be determined. Biologists believe that the greater the similarity between the amino acid sequences of two organisms, the closer their relationship. Conversely, the greater the differences, the more distant the relationship. Further, biologists have found that such biochemical evidence compares favorably with other lines of evidence for evolutionary re1ationships In this investigation, you will compare amino acid sequences in proteins of several vertebrates. You will also study amino acid differences and infer evolutionary relationships among some diverse organisms. Comparing Amino Acid Sequences 1. Examine Figure 1, which compares corresponding portions of hemoglobin molecules in humans and five other vertebrate animals. Hemoglobin, a protein composed of several long chains of amino acids, is the oxygen-carrying molecule in red blood cells. The sequence shown is only a portion of a chain made up of 146 amino acids. The numbers in Figure 1 indicate the position of a particular amino acid in the chain. 2. In Data Table 1, notice that the abbreviated names of the amino acids in human hemoglobin are printed. 3. Compare the human sequence to the sequence of each of the other species. Circle any difference when compared to the human amino acids. 4. Turn your paper 90-degrees to the left and shade in the number of boxes that corresponds to the total number of differences between humans that the other organisms. 5. After you are done graphing, answer the questions. Activity 3. Evidence of Evolution Molecular Data – Use your notes, book and the Internet to answer the following questions about molecular evidence. In all four examples, males are “showy” and females are “choosy”. Males perform displays that females use to select a mate. If females don’t choose males based on their behavior/display, then their gametes remain separate and they become reproductively isolated. Reproductive isolation over a period of time can lead to new species. Activity 6. Click on two (minimum) of the video links. Describe how the behaviors you observe can lead to speciation. Bird of Paradise - https://www.youtube.com/watch?v=W7QZnwKqopo Riflebird - https://www.youtube.com/watch?v=7XhPHWY4RuM MW Bird - https://www.youtube.com/watch?v=eI_quJRRGxk Peacock spider - https://www.youtube.com/watch?v=9GgAbyYDFeg (You can jump through parts to see the behavior) Answer: Plant Species 2  Species 1: - enzyme, 4 aa different, no common DNA bands  Species 2: + enzyme, 1 aa different, all DNA bands common  Species 3: + enzyme, 3 aa different, 1common DNA band Based on the data collected, label the phylogenetic tree.  Place Unknown, Species 1, Species 2 and Species 3 on the tree to represent the possible evolutionary relationships  Identify the species that diverged from a common ancestor most recently. Place the purple circle over the common ancestor.  Place the red bar for Enzyme M onto the tree to make a cladogram. Enzyme M Activity 7. Use the information in the data table below to construct a phylogenetic tree, then cladogram.