2History of Evolutionary Thought Before 1850, most people believed…Earth formed by supernatural events and never changedEarth only a few thousand years oldEach species was made to fit its environmentSpecies never changed and did not go extinct
3Early Scientists’ Ideas Darwin deserves credit for the Theory of Evolution as we know it todayHe was not the first to come up with the idea:Carolus Linnaeus proposed a new system of organization for plants and animals based on their similarities (noticed relationships)Erasmus Darwin considered how organisms could evolve through mechanisms such as competitionJean-Baptiste Lamarck presented evolution as occurring due to environmental change over long periods of time
4Carolus LinnaeusDeveloped a classification system for the huge variety of living things he foundWrote book Systema Naturae in 1735 to reveal his classification systemThere are currently 1.9 million species that have been identified using his methodLinnaeus’s system of classification reflects evolutionary relationships
5Jean Baptiste LamarckA French naturalist who proposed that populations of species evolveHis idea proposed:Changes in an environment cause an organism’s behavior to change, leading to greater use or disuse of a structure or organ.The organism would pass on these acquired changes to its offspring, so a species would change in time.Idea called “Evolution by inheritance of acquired characteristics”Wrong on several accounts
7- Darwin’s TheoryDarwin’s VoyageCharles Darwin sailed on the Beagle, from England to the Galápagos Islands.
8Darwin’s important observation The diversity of living thingsThe remains of ancient organismsThe characteristics of organisms on the Galapagos Island.He wrote a book The Origin of SpeciesAll of his observations led him to develop one of the most important scientific theories of all time: the theory of evolution by natural selection.
9Species is a group of similar organisms that can mate with each other and produce fertile offspring Adaptation is a trait that helps an organism survive and reproduce.
10Darwin’s FinchesWhen Darwin traveled to the Galapagos he took interest in the finchesHe noticed the finch species on the islands were different, but all resembled one from S. America.Darwin thought some migrated and new species evolved.
11Darwin’s Finches This is what Darwin proposed: Finches migrated from South America to the islands.Populations on different islands adapted to different environments and food sources they found.Those that could survive passed on their genes.Those that couldn’t survive perished.
12Darwin’s FinchesOver time different mutations accumulated in the different finch populations on the different islands.The populations diverged, or became more and more different from each other.
13Darwin’s FinchesThe populations on the islands became so different they no longer mated if they metSeveral new finch species evolved from a common ancestor from S. AmericaThis is an example of macroevolution.
14EvolutionDarwin hypothesized, the species gradually changed over time and became better adapted to the new conditions.The gradual change in a species over time is called evolution.
16Fossils is the preserved remains or traces of an organism that lived in the past. Extinct: are no longer living species.Transitional species- species that have been found in the fossil record that are intermediates between two other species in the evolutionary process
17Fossil record Layers of sedimentary rock contain fossils new layers cover older ones, creating a record over timefossils within layers show that a succession of organisms have populated Earth throughout a long period of time
18“Dating Fossils”Relative Dating: the age of the fossil is determined by comparing its placement with that of fossils in other layers of rock.
19Radioactive Dating: calculating the age of the fossil based on the amount of remaining radioactive isotopes it contains.Half-life: is the length of time required for half of the radioactive atoms in a sample to decay.
21Similarities in Development All animals evolved from a common ancestor:the most recent ancestral species from which two or more different species evolved
22Anatomical EvidenceAnatomical evidence- evidence for evolution which is based on similarities and differences between the physical structures of different species.What can we tell about the relatedness of the three species below?
23Homologous Structures: are body parts that have the same basic structure. Homologous structures in different organisms are clues that these organism evolved from a common ancestor.
24Homologous structures Similar structureSimilar developmentDifferent functionsEvidence of close evolutionary relationshiprecent common ancestor
26Vestigial Structure: are body structures that seem to have no function. Evidence that it once functioned in the ancestors of the organisms that did have them.
27Analogous structures Separate evolution of structures similar functions with similar external formdifferent internal structure & developmentdifferent originno evolutionary relationshipDon’t be fooled by their looks!Solving a similar problem with a similar solution
28Molecular record Comparing DNA & protein structure compare common genescytochrome C (respiration)hemoglobin (gas exchange)Closely related species have sequences that are more similar than distantly related species
29Artificial selectionIn artificial selection, nature provided the variation, and human selected those variations that they found useful“descendants” of wild mustard“descendants” of the wolf