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14.1 • I can recognize patterns of change in populations over time • I can give examples of evidence that supports evolution • I can describe fossils of early human ancestors • The changes in a population over time • An organism changes as it grows and develops, but this is NOT evolution • Evolution occurs within populations • As organisms in a population die off, new organisms are born into it Levels of Organization Biosphere Ecosystem Community Population Organism • Genes determine the traits of all living things • Evolution involves changes in a population’s gene pool • Genes can be changed by radiation, chemicals in the environment, and if they are copied incorrectly • Mutations in gametes do not affect the parent, but instead they get passed on to the offspring • Mutations can cause harmful changes in traits • A lethal mutation is one that results in an organism’s death • Most mutations, though, are favorable and are passed on to offspring • As the mutation is passed on to future generations, it becomes more and more common with the population • If a population’s environment changes, members of the population that have certain favorable traits maybe more likely to survive • Evolution occurs slowly as these favorable traits are passed on from one generation to the next • A change in the environment may split a population into two isolated groups • A large river, or canyon may form and divide a population • The single population now becomes two populations that have no contact with each other • Different mutations can occur which result in different genes • Sometimes a population can be divided if organisms move out of the area • For example, organisms may travel from the mainland to a neighboring island • Over time, if enough change occurs, the island population may evolve into a new species • Evolution • Lethal Mutation • Geographic Isolation • Self-Check Questions #1-5 pg. 316 • COMPLETE SENTENCES 14.2 • Fossils are the remains or traces of organisms that lived in the past • Fossils are found in rock, tree sap, and other materials • Fossil comes from the Latin word fossilis, meaning “dug up” • Bones and teeth can remain as fossils for millions of years • Fossils can be found in mud and bits or rock, called sediment, at the bottom of water • Over time, layers of sediment harden into rock and leave a type of fossil called a mold • Animals and insects have also been found in hardened tree sap and frozen in ice • Paleontologists are scientists who study life in the past, or fossils • Their findings have formed a fossil record, which is a history of life on Earth, based on fossils that have been discovered • Fossil records also show how organisms have changed over time • Life on Earth dates back 3.5 billion years (geologic time scale) pg. 319 • Scientists can tell how old a fossil is by comparing its location in rock • Fossils in lower layers of rock are older than fossils in upper layers of rock • Scientists can also use radioactive materials to date fossils • Radioactive materials give off energy as they change to another substance over time • When a species disappears, it is said to be extinct • A fossil record will show when different species lived and then disappeared from Earth • As species become extinct, new species appear • Mass extinctions (large numbers of species became extinct) are caused by major changes in environment • Fossils show how groups of organisms have changed over time • Horses and humans are examples (pg. 321) • Scientists learn more about fossils by comparing them to living organisms • The look for similar structures, such as teeth and bones • Fossils have proven that certain species have evolved: • Certain fish have evolved into amphibians • Reptiles have evolved into mammals • Some reptiles have evolved into birds Fossil Sediment Fossil Record Extinct Self-Check Questions #1-5 pg. 323 COMPLETE SENTENCES