Reading Science! Name: Date: Darwin s Fancy with Finches Lexile 1190L

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1 7.11/.12: daptation of Species Name: ate: arwin s Fancy with Finches Lexile 1190L 1 2 Whales are mammals that live in water and can hold their breath underwater for a long time, yet need to breathe air from the surface of the ocean in order to live. Evidence suggests that the modern-day whale s ancestors lived on land. White hair in animals is due to the loss of chemical that causes the hair to be colored. iologists declare that the ancestors to polar bears lost their dark pelt over time to a theory known as natural selection. This theory was defined in harles arwin s book On the Origin of Species by 1. Geospiza magnirostris. 3. Geospiza parvula. 2. Geospiza fortis. 4. erthidea olivacea Finches from Galapagos rchipelago Means of Natural Selection in Natural selection is the process that is responsible for the evolution of adaptations of organisms to their environment over time. Evolution is changes in inherited features of a species. Natural selection plays a role in the origin of new species. Essentially, natural selection means that the organisms with the strongest dominate traits are the ones that will be able to sustain the environmental conditions over time, thus survive. harles arwin was a mere 22 years old in He developed his theory of evolution as a result of a survey he conducted while sailing as a naturalist aboard the HMS eagle His job was to search for and collect samples of plants and animals he found on the ship s journey around the world. He was particularly amazed by the unusual animals and plants he found in the Galápagos Islands, located 600 miles west of the coast of Ecuador. arwin was especially fascinated by fourteen types of a small bird he identified as varieties of finch. He pondered upon how there could be so many different, 1

2 7.11/.12: daptation of Species yet similar, species of finches living in such close proximity of each other in this chain of islands. For twenty years after his voyage, arwin studied his collection of animals and plants. His findings resulted in a hypothesis that eventually became known as the theory of evolution by natural selection. Even today, this theory is one of the most important concepts in studying life science Four factors govern natural selection: 1) In general, organisms produce more offspring than can survive; 2) variations of a species are found among individuals; 3) these variations contribute to the survival and reproduction of individuals; and 4) over time, with the succession of generations, variations that enhance survival and reproduction in the offspring will become increasingly widespread in the population. This is particularly true when variations provide a survival advantage to individuals within the environment. Variations result from changes in an organism s N, which is also known as mutation. Variations may include the organisms color, chemical make up, shape, and size. amouflage coloring, for example, is a protective adaptation that allows the organism to blend in with its environment, which affects its ability to avoid predators. Those individuals that successfully survive and produce offspring, will pass on those variations through their genes. This process is what is referred to as an adaptation of species. arwin s finches are the classic example of illustrating how this can happen. He examined the variations in the beak sizes and shapes of the Galápagos finches. ll fourteen species of these finches are closely related, and they live in a changing environment. The environment underwent periods of severe drought as well heavy, prolonged rains of El Niño. These impacted the geography, climate, and vegetation of the islands. Those finches that couldn t adapt, perished. Human activity was generally absent, and therefore had no effect on these species. Thus, biologists conclude that the key factors that shaped adaptations in the finches could be attributed strictly to the forces of environmental change and natural selection. arwin marveled most at the size of the beaks and varied diets of the different species of the finch he 2

3 7.11/.12: daptation of Species found on the islands. His theory included evidence supporting how one species of finch, a common ancestor, had likely evolved into many different species is Galápagos and the surrounding islands. His finches main adaptation appeared in the shape and type of beak as the birds adapted to the local food sources on each island. The food types that grew on each island were driven by environmental conditions. 6 Today, adaptations of species is clearly seen in our every day lives. For example, some insects evolved over hundreds of years to resist various chemicals used to exterminate them. Their resistance to various insecticides has mad it more and more difficult to control them, resulting in financial loss for the agricultural industry and, in some cases, an inability to control the destruction of crops. daptations also show up in human health. iologists have seen how harmful bacteria and viruses have evolved increasing resistance to antibiotics or other drugs used against them. The most obvious example is the epidemic spread of the HIV virus, which medical scientists testify is capable of evolving rapidly to resist drugs that once were effective against it. This antibiotic resistance is another excellent example that illustrates arwin s natural selection process. 3

4 7.11/.12: daptation of Species 1 Natural selection is a process that happens in the absence of environmental conditions. a single process of adaptation within an individual. the survival of the fittest. an ability to predict the outcome of a defined species over time. 3 arwin, through his collection of samples and findings, taught us that natural selection is how species survive over time. evolve by adapting to their environment over time. plays a role in the origin of new species. oth and 2 In 1859, arwin s controversial book, On the Origin of Species by Means of Natural Selection, illustrates the importance of variations in organisms. the explanation of design in nature. how species evolve by adapting to their environment. ll the above 4 arwin concluded that the chief reason his finches did not become extinct was due to ample food supply. climate control. absence of predators. the lack of human activity on the islands. 4

5 7.11/.12: daptation of Species 5 This reading suggest that the factors governing natural selection include all except which of the following: Organisms successfully reproduce themselves Organisms produce more offspring than can survive Over time, variations in the offspring will become increasingly widespread in the population Variations are found in an individual 6 From the reading of this passage, you now know that examples of natural selection would include the whale, a mammal who lives in the water. some insects resistant to pesticides. antibiotic resistance in the human body as seen in HIV patients. ll the above 5