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Think about it… Open your manuals to page 112. Describe the fossil record of your own life that might be found 65 million years from now. What items, or artifacts, might be likely to survive? What kinds of things would decay and disappear? Do you think your fossil record would produce an accurate picture of your life? What might be missing? Change over Time and how Population Changes Happen State Standard: SPI 5.3- Analyze data on levels of variation within a population to make predictions about survival under particular environmental conditions. Changes over time ● For thousands of years, people have observed change in living things over time. ● The fossil record shows organisms developing new traits & losing others. ● Therefore - as populations change over time, new species may form. Thus, newer species descend from older species Fossils ● Fossils are the imprints or remains of once-living things often preserved in sedimentary rocks. ● They help us unravel the past ● Fossils can suggest the climate of a region at the time of the fossil. ● Different fossils will be found in different sediment layers and/or different regions. Older fossils will be in the bottom layers. Fossil Fossil Fossil The Fossil Record ● By studying fossils, scientists have made a timeline of life known as the fossil record. ● The fossil record organizes fossils by their estimated ages and physical similarities. ● Comparing organisms in the fossil record can reveal how organisms have changed over time. Evidence of Ancestry ● Evidence of common ancestors can be found in fossils and in living organisms. Many species have common physical features. ● The human arm, whale flipper, horse leg and bird wing all have the same bone shape, suggesting a common ancestor. ● This is called a homologous structure. ● Embryo’s (organisms at an early stage of development) also support the idea of common ancestry because of a similar look. • Evidence that groups of organisms have common ancestry can be found by comparing the groups' DNA. African wild dog Dhole Ethiopian wolf Coyote Gray wolf Dog Golden jackal Black-backed jackal Side-striped jackal Which two species are most closely related? 2 answers possible. Fig. 23-6, p. 491 Charles Darwin’s Theory • As the naturalist–a scientist who studies nature–on board the British ship HMS Beagle, Darwin made several observations that shaped his theory. ● One noted observation was that all the finches on the Galapagos island looked about the same except for the shape of their beak. ●This lead to a conclusion that all the finches were descendants of the same original population. ●The shape of the beaks were adaptations for eating a particular type of food (Ex. long beaks were used for eating insects, short for seeds) ● Darwin realized organisms best matched to their environments are more likely to survive & reproduce. ● Hence – Natural Selection Genetics and Inherited Traits ● Darwin knew that organisms inherited traits, but not how they inherit traits. ● He knew there was great variation among organisms, but not how that variation occurs. ● Today, we know that variation happens as a result of the exchange of genetic information as it is passed from parent to offspring. ● The process called selection happens when only organisms that carry these genes can survive to reproduce. ●A trait is a form of a hereditary characteristic. ● The practice by which humans select plants or animals for breeding based on desired traits is selective breeding. Changes in Population ● Changes in population can occur when a new force affects the survival of individuals in the population. ● Darwin realized that any species can produce many offspring. He also knew that the populations of all species are limited by starvation, disease, competition, and predation. ● Only a limited number of individuals live long enough to reproduce. Thus, the survivors are special. ● Therefore - Darwin reasoned that the offspring of the survivors inherit traits that help the offspring survive in their environment. Example-Insecticide Resistance Forming a New Species ● Sometimes, drastic changes can form a new species. ● In the animal kingdom, a species is a group of organisms that can mate with each other to produce fertile offspring. ● A new species may form after a group becomes separated from the original population. This group forms a new population. ● Over time, the new population adapts to its new environment. ● the new population & the original population differ so greatly that they can no longer mate successfully. The new population may then be considered a new species. ● The formation of a new species as a result of change over time is called speciation Putting it together. . . Complete the following skill sheet to reinforce these concepts.