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Evolution Part II Mrs. Cabak and Mrs. Osakwe Campbell Middle School Life Science th 7 grade How does Natural Selection affect the evolution of species on Earth? COEVOLUTION The evolution of two or more species that is due to mutual influence, often in a way that makes the relationship more mutually beneficial… The ant and acacia tree are examples: the ant protects the tree and the tree has special structures that make food for ants. Flowers and pollinators are also examples of coevolution. Flower and pollination PUNCTUATED EQUILIBRIUM The theory that speciation occurs in spurts of major genetic alterations that punctuate long periods of little change. Punctuated equilibrium is a model of evolution in which short periods of drastic change in species, including mass extinctions and rapid speciation, are separated by long periods of little or no change. NATURAL SELECTION The process by which Individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do; a theory to explain the mechanism of evolution. There are four parts: overproduction, inherited variation, struggle to survive, and successful reproduction. VARIATION Marked difference or deviation from the normal or recognized form, function or structure. Darwin noticed that the animals and plants on the Galápagos Islands were a lot like those in Ecuador. However, they were not exactly the same. The finches of the Galápagos Islands, for example, were a little different from the finches in Ecuador. And the finches on each island differed from the finches on the other islands. The beak of each finch is adapted to the way the bird usually gets food. ADAPTATION An alteration or adjustment in structure or habits, often hereditary, by which a species or individual improves its condition in relationship to its environment. Populations constantly undergo natural selection. After two groups have separated, natural selection may act on each group in different ways. Over many generations, the separated groups may evolve different sets of traits. If the environmental conditions for each group differ, the adaptations in the groups will also differ. SPECIATION The evolutionary formation of new biological species, usually by the division of a single species into two or more genetically distinct ones. Speciation often begins when a part of a population becomes separated from the rest. The process of separation can happen in several ways. For example, a newly formed canyon, mountain range, or lake can divide the members of a population. GEOGRAPHIC (ALLOPATRIC) SPECIATION Evolution of two or more species from a single species following geographic isolation. GRADUALISM The view that speciation proceeds by imperceptibly small, cumulative steps over long periods of time rather than by abrupt, major changes. ABSOLUTE (RADIOISOTOPE) DATING Scientists can determine the age of a fossil more precisely. Absolute dating is a method that measures the age of fossils or rocks in years. In one type of absolute dating, scientists examine atoms. Atoms are the particles that make up all matter. Atoms, in turn, are made of smaller particles. Some atoms are unstable and will decay by releasing energy, particles, or both. When an atom decays it becomes a different, and more stable, kind of atom. Each kind of unstable atom decays at its own rate. The time it takes for half of the unstable atoms in a sample to decay is the halflife of that type of unstable atom. By measuring the ratio of unstable atoms to stable atoms, scientists can determine the approximate age of a sample of rock. RELATIVE DATING The proper chronological placement of a feature, object, or happening in the geologic time scale without reference to its absolute age. Sedimentary rock has many layers. The oldest layers are usually on the bottom. The newest layers are usually on the top. The layers can tell a scientist the relative age of fossils. Fossils found in the bottom layers are usually older than the fossils in the top layers. So, scientists can determine whether a fossil is older or younger than other fossils based on its position in sedimentary rock. Estimating the age of rocks and fossils in this way is called relative dating. FITNESS The extent to which an organism is adapted to or able to produce offspring in a particular environment.