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Ch. 15 The modern theory of evolution is a fundamental concept in biology. This is the one, unifying concept of biology that allows us to make sense of the natural, biological world. Took a job as a naturalist on the English ship, HMS Beagle, which sailed to S. America on a scientific trek. The biological specimens (animals) that he studied in the Galapagos Islands were specifically interesting to Darwin. These animals were distinctly their own species but were similar to species found elsewhere, which led Darwin to believe that organisms could change over time. He spent the next 22 years studying how animals could change over time. Darwin used an idea proposed by Thomas Malthus about human population growth to explain that through competition and limited resources, only some are able to survive to reproduce. Darwin experimented with breeding pigeons and discovered that different populations had different traits and that these traits are passed down to future generations. Breeding organisms with specific traits in order to produce offspring with identical traits is known as artificial selection. Darwin believed there was a force in nature that was similar to this. Natural Selection is the mechanism by which traits within a population change over time. Natural Selection Though another naturalist, Alfred Russell Wallace, was working on similar work and added to Darwin’s work, Charles Darwin was the first to publish his book on the subject, On the Origin of Species by Natural Selection in 1859. Difficulties Because evolution is a slow and gradual process, it is difficult for humans to directly observe. Due to the immensity of time in relation to the rather short span of human life, it is hard to comprehend the time it involves. It can sometimes be considered contradictory to personal religious beliefs. Adaptation Definition: any variation that aids an organism’s chance of survival in its environment. Evolution explains how they develop in the 1st place. Develop over many generations. Mimicry Definition: structural adaptation that enables one species to resemble another. ex: yellow jacket wasps and syrphid flies Camouflage Definition: adaptation that allows an organism to blend into its surroundings ex: leaf frog Resistance Bacteria develop resistance to antibiotics. Insects and plants develop resistance to pesticides. Is direct evidence of evolution. The shorter the lifespan of an organism, the faster adaptations can occur. (ex: bacteria) Fossils Provide a record of early life and evolutionary history. Like a puzzle, even with missing pieces we can envision the overall picture. Anatomy Homologous Structures Structural features with a common evolutionary origin. the ex: forelimbs of whales and crocodiles Shows evidence of a common ancestor, which shared the same characteristic. Always similar in arrangement and sometimes in function. Analogous Structures Structural features that have evolved independently of each other. ex: wings of a butterfly and wings of a bat Have similar function but not arrangement. Vestigial Structures Structural features that have no function in the present-day organism but that was useful to its evolutionary ancestors. ex: eyes of moles / cave fish or pelvic girdles in pythons Embryology Similarities in early embryos suggest evolution from a common ancestor Biochemistry The sequences of RNA or DNA can be compared between organisms. The closer in sequence a gene is, the more closely related the organisms are to each other. Homology vs. Analogy Jellyfish Fossils Vestigial Structures Embryology Biochemistry