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BELL WORK: Answer the following question: Two species of mice live in a field in the middle of East Texas. One mouse species is white with black spots, the other is brown with white spots. After a year, the population of white mice has dramatically decreased, while the population of the brown mice has slightly increased. Why might this be happening? CO: I will analyze how evolution occurs in a population. I will examine evidence for evolution. LO: I will talk about evolution with the class. I will write notes about evolution. Let’s chat about our potato farms! Evolution: What is it? Evolution: change in heritable traits of a population across generations (over time). Charles Darwin: contributed more to our understanding of evolution than anyone else. • Darwin traveled, made observations and collected evidence that led him to propose his revolutionary process in a book called On the Origin of Species Population size is limited by environmental resources. *What are some examples of environmental resources? Fitness: the ability of an organism to survive and reproduce. • Fitness is the result of adaptations. Adaptation: any inherited characteristic that increases an organism’s chance of survival. Successful adaptations: - enable organisms to become better suited to their environment - increase an individual’s ability to survive and reproduce. The Primary Mechanism of Evolution: Natural Selection Natural selection: the process by which individuals with characteristics that are not well suited to their environment either die or leave few offspring. 1. Also referred to as survival of the fittest. 2. It is not seen directly, but only observed as changes in a population over a long time. Bunny Simulation If only one species is considered the "fittest", why do we still have so many variations among species? Why do some birds have very long pointy beaks, while other birds have short flat beaks? Evidence for the Theory of Evolution Evidence for evolution can be found in: 1. the fossil record 2. biogeography (the geographical distribution of living species) 3. homologous structures of living organisms 4. similarities in early development, or embryology. 5. molecular (DNA) homologies 1. Fossil record By comparing fossils from older rock layers to fossils from younger layers, researchers have discovered many hundreds of transitional fossils that document various intermediate stages in the evolution of modern species from organisms that are now extinct. 2. Biogeography: study of the geographical distribution of plants and animals Darwin observed this with finches and tortoises in the Galapagos Islands. He noticed that there were several different species of birds/tortoises on the islands that were similar to each other, but had different adaptations. He thought that they evolved from a common ancestor to best fit the environment of the island they were on. We can see this in other species around the world too. 3. Homologous structures: bones and muscles that have similar structures but perform different functions 4. Embryonic Homologies: Different organisms develop from similar starting forms (embryos) 5. Molecular Homologies: similarities in DNA sequences among different organisms *Because organisms evolved from a common ancestor, we find similarities in the DNA sequence of all living organisms. *The more of a DNA match we see, the closer of a relationship the organisms have.