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Evidence of Species Change Evidence of Evolution What is evolution? Evolution is change over time Scientific theory of evolution explains how living things descended from earlier organisms Evidence of Evolution What evidence supports evolution? Fossils Fossils are preserved remains or traces of organisms that lived in the past Scientists can infer the structure of ancient organisms by looking at fossils Fossil evidence supports the idea that living things evolved from earlier organisms Evidence of Evolution Evidence of Evolution What evidence supports evolution? Similarities in DNA and protein Scientists infer that species inherited many of the same genes from a common ancestor Genes are segments of DNA that determine the characteristics in an organism The more similar the sequence of bases in a strand of DNA, the more closely the organisms are related Genes determine the types of protein produced Proteins are made of amino acids Scientists compare sequences of amino acids to determine closeness Evidence from DNA and protein structures has confirmed conclusions based on fossils, embryos, and body structure Evidence of Evolution Section of Cytochrome c Protein in Animals The table shows the sequence of amino acids in one region of a protein, cytochrome c, for five different animals. Each letter corresponds to a different amino acid in the protein. Evidence of Evolution What evidence supports evolution? Similarities in body structure An organism’s body structure is its basic body plan Similar structures that related species have inherited from a common ancestor are called homologous structures Evidence of Evolution Homologous Structures The bones in a bird’s wing, a dolphin’s flipper, and a dog’s leg have similar structures. Which bones in the dog's leg match those in the flipper and which match those in the wing? Evidence of Evolution What evidence supports evolution? Similarities in early development Scientists infer evolutionary relationships by comparing the early development of different organisms Evidence of Evolution Can you tell which of these four embryos is: a. pig b. chicken c. turtle d. fish Evidence of Evolution Similarities in Development These four organisms all look similar during their early development. What are similarities and differences among them? Evidence of Evolution - Classwork 1. 2. 3. Compare and contrast the bones of a bird’s wing and a seal’s flipper. What can scientists infer from the similarities between these two structures? Describe how DNA evidence might be used to confirm scientists’ conclusions about any relationship between birds and seals Darwin’s Theory What was Darwin’s hypothesis? In 1831, the HMS Beagle set sail from England on a five year trip around the world Naturalist Charles Darwin was on board. He Was amazed by the diversity of living organisms (different from England) Saw fossils of animals (that resembled the bones of then-living organisms) that had died long ago Compared species living on the Galapagos Islands with those living on the mainland of South America Darwin’s Theory What was Darwin’s hypothesis? Compared species living on different Galapagos Islands Concluded that different finches he found on the Galapagos Islands were descended from the same finches he found on the mainland of South America Different finches developed different beak shapes and sizes depending on the food they ate Darwin’s Theory What was Darwin’s hypothesis? Beak shape is an example of an adaptation, a trait that increases an organism’s ability to survive and reproduce Darwin’s hypothesis was that species change over many generations and become better adapted to new conditions This hypothesis had become known as the Scientific Theory of Evolution, because it is a well-supported and widely accepted explanation Darwin’s Theory Galápagos Finches The structure of each bird’s beak is an adaptation to the type of food the bird eats. Match each finch to the type of food you think it eats. Darwin’s Theory What was Darwin’s hypothesis? Update Peter Raymond Grant and Barbara Rosemary Grant, British evolutionary biologists have spent six months of the year each year since 1973 capturing, tagging, and taking blood samples of the finches on the island. They have demonstrated how very rapid changes in body and beak size in response to changes in the food supply are driven by natural selection. Darwin’s Theory What was Darwin’s hypothesis? Darwin studied domestic animals produced by artificial selection (selective breeding) In artificial selection, only organisms with desired traits are bred A trait is a specific characteristic that an organism can pass to its offspring Ideas about Evolution What was Darwin’s hypothesis? Species Individuals of the same species can interbreed and have fertile offspring Individuals of the same genus, but not the same species, may be able to interbreed, but their offspring are not fertile Ideas about Evolution What was Darwin’s hypothesis? Artificial selection All dogs and wolves are Canis lupus Wolves are Canis lupus lupus Domestic dogs are Canis lupus familiaris Since they are all the same species, wolves and dogs they can interbreed and have fertile offspring The wolf Great Dane Chihuahua Breeds of domestic dogs Darwin’s Theory - Classwork How does artificial selection support Darwin’s hypothesis?