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Transcript
Evidence shows change The continuing process of genetic change in a population of organisms over long periods of time is called: EVOLUTION History of Evolution • At first most people believed that species could not change, that there were a fixed number of species, and that each species had a given set of traits that remained with it forever. •As stronger evidence became more available, they began to see living things change over long periods of time. •Jean Babpiste de Lamarck and Charles Darwin led the way in the search for the mechanisms that caused this change. Jean Baptiste de Lamarck 1809 –proposed a hypothesis to explain the variation in organisms. Acquired Characteristics- traits that developed during a lifetime could be passes on to the offspring. I.e. giraffes stretched their necks over a lifetime to reach food. They then passed on the longer neck trait to their offspring. Rejecting Lamarck’s Hypothesis Large amounts of data showed that acquired traits are not hereditary. Charles Darwin 1836 took a voyage on the H.M.S Beagle to the Galapagos Islands and collected a lot of data. Natural Selection- a mechanism for change in a population that occurs when individuals with the most favorable variations for a particular environment survive and pass these traits on to offspring. Natural Selection 1. Variations exist within populations. 2. Some variations are more advantageous for survival and reproduction than others. 3. Organisms produce more offspring than can survive. 4. Over time, offspring of survivors will make up a larger proportion of the population. Peppered Moths Variation in moths some black some light colored. In 1850 most were light. Industrial revolution covered trees with smoke and soot. Now the dark moths were better suited for the environment. Play Natural Selection Game In this simulation of natural selection, an equal number of light and dark Peppered Moths are released in a forest. You are a bird in the forest, trying to eat as many moths as possible. To eat, click on the moth. The current population of light and dark moths are shown at the bottom of the screen. Peppered Moths in a lichen covered forest Peppered Moths in a dark, soot covered forest Mechanisms of Evolution The change in the genetic makeup of a population of organisms over long periods of time is called: EVOLUTION When allele frequencies change the genetic equilibrium is altered and evolutions has taken place. 2. Changes in genetic Equilibrium a. Mutations are changes in genetic material of an organism. Provides new genetic material in a species. Changes in genetic equilibrium b. Genetic Drift – the change in allele frequencies of a population as a result of chance processes. The survival and reproductions of organisms is subject to unpredictable accidents See an example Changes in genetic equilibrium continued c. Gene Flow is the movement of genes in and out of the gene pool. Gene flow increases genetic variation within a population Patterns of Evolution Patterns of Evolution 3. Adaptive Radiation – species adapting to different environments and become a new species. Recap video Evidence for change Fossils- provide scientists with strong records of the earth’s past. A fossil is the remains of an organism preserved in the earth’s crust Where are fossils found? Found in layers of sedimentary rocks. Organisms were buried in layers of mud and or sand. 4 types of fossils Imprint Mold Cast Petrified Imprint Fossils The soft parts of buried organisms decay and leave an imprint in the stone. I.e. animal tracks and plants Mold fossils The hard parts of an organism decay and leave indentation in the rock. Cast Fossil A mold fossil fills with mineral or rocks Cast Dinosaur eggs Petrified Fossils Highly porous materials like bones or wood can become petrified if they are buried quickly and thoroughly. More Petrified Fossils Relative Dating Relative dating tells scientists if a rock layer is "older" or "younger" than another. fossils found in the deepest layer of rocks in an area would represent the oldest forms of life in that particular rock formation. Evolution of the horse Living organisms resemble most recent fossils in the line of descent; underlying similarities allow us to trace a line of descent over time. Absolute Dating The use of radioactive isotopes to date fossils and rocks. A radioactive isotope is an atom with an unstable nucleus and decays at certain rate. Half-Lives of Selected Radioactive Isotopes Isotope Half-Life 14-C 5730 y 24-Na 15.0 h 32-P 14.3 d 36-Cl 3.1 x 10+5 y 40-K 1.28 x 10+9 y 45-Ca 165 d 226-Ra 1.62 x 10+3 y 235-U 7.1 x 10+8 y 238-U 4.51 x 10+9 y 239-Pu 2.44 x 10+4 Homologous Structures Structures that are similar and are derived from the same body parts. Vestigial Structure Body parts that are reduced in size and serve no apparent function. I.e – Human tail bone – no function Examples of Vestigial Structures Human appendix useless yet in other mammals, including primates, it is necessary to aid in digestion of high cellulose diet Human external ear muscles still present but useless Humans have tailbones and some babies occasionally have tails Human wisdom teeth vestigial compared to other primates Some snakes have skeletal limbs Cave dwelling crayfish have eyestalks yet no eyes Analogous Structures Body part that have similar functions but originate from different structures. Examples of Analogous structures structures "fitted" for a particular purpose tend to be similar, regardless of origin flippers in dolphins, penguins and fish. wings have developed independently in insects, reptiles, birds, and bats Embryonic Development Gill slits and tail in human embryo show similarities of embryos of dissimilar organisms. Biochemical Analysis or DNA/RNA Comparisons •Comparison of nucleic acid sequences shows similarities between species. The more closely related organisms are, the more similar is their biochemical makeup •Cytochrome C, a protein, The more closely related organisms are, the more similar their amino acids are. •Humans differ by 1 nucleotide compared to monkeys •Humans differ by 19 nucleotides compared to turtles