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Evidence for evolution (Sect. 5.3) Scientists compare 1. body structures, 2. development before birth and 3. DNA sequences to determine the evolutionary relationships among organisms. Classify the following: Trout, catfish, frog, snake, whale, human, cardinal, turtle, salamander, shark, dolphin, bat, blue jay, How many of you grouped them by movement: SWIMMERS Trout Catfish Whale Shark dolphin FLIERS cardinal bat blue jay HOP/CRAWL/SLITHER UPRIGHT frog human snake turtle salamander Or by: FISH Trout Catfish Shark AMPHIBIANS REPTILES frog snake salamander turtle BIRDS cardinal blue jay bat Human MAMMALS whale dolphin ANOTHER WAY…1. SIMILARITIES IN BODY STRUCTURE: An organism’s body structure is its basic body plan (ex. How its bones are arranged.) The 5 classes of vertebrates (fish, amphibians, reptiles, birds and mammals) all have a similar body structure: Internal skeleton w/a backbone. All these inherited similarities in structure from an early common vertebrate ancestor. These are called HOMOLOGOUS STRUCTURES. 2. Similarities in Early Development Scientists can also make inferences about evolutionary relationships by comparing the early development of different organisms. See pg. 166-167 3. Similarities in DNA Scientists infer that the species inherited many of the same genes from a common ancestor. Genes are made of DNA. By comparing the sequence of nitrogen bases in the DNA of different species, scientists can infer how closely related the species are. The more similar the sequences, the more closely related the species are. See page 168-Fig. 15 Combining evidence Scientists have combined evidence from fossils, body structures, and early development, and DNA and protein sequences to determine the evolutionary relationships among species. Another example of how scientists combined evidence from different sources is shown in the branching tree. A branching tree is a diagram that shows how scientists think different groups of organisms are related. Below image from Prentice Hall Life Science.
