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Lemarck’s Theory • Organisms develop new organs or change their structures to meet changes in their environment (use it or lose it) • Inheritance of acquired traits – traits acquired during a lifetime could be passed on to next generation FOLLOW DIRECTIONS! • Write your name at the bottom • When you get a paper, draw what you see as closely as you can on your own paper – Pass their paper back when you are done with it • Do NOT trace • Do not let the people behind you see what you are copying • Pay attention and DON’T TALK! Taxonomy Grouping of organisms based on similar characteristics. Species Organism that has at least one characteristic not shared with any other organism Characteristics Controlled by proteins Proteins Made of amino acids Amino Acids Coded for by a gene Gene Set of nitrogen bases in DNA molecule Mutation Change in nitrogen bases through any number of causes • Darwin traveled 5 years on the Beagle as its naturalist • He sent samples back • He wrote a 200 page essay on his observations • Darwin published his book entitled The Origin of Species • all species reproduce in excess of the numbers that can survive • all organisms compete for limited resources • variations exist within a species • environment selects for the more advantageous variations = better suited leave more offspring (fitness) Video Darwin’s example of Natural Selection Galapagos Island Finches, p.305 – 13 species – closely resemble 1 species living on South American mainland – The mainland species strayed and evolved into 13 different species • Each island had slightly different conditions • Best suited (most fit) to environ. leave most offspring – Variation is heritable – Natural Selection leads to adaptation, which leads to new species Conditions determine Characteristics •Related organisms becomes less alike • Change in gene frequency / species over time • Unifying theory of biology based on scientific observation. Change in a population’s alleles over a period of time Evolution which gives rise to new species Needed for evolution to occur Mutations – changes in nucleotide sequence of DNA Recombination – reshuffling of genetic material during meiosis Gene flow – gene frequency changes due to immigration from other populations Needed for evolution to occur Natural selection – organisms with less advantageous traits (genes) survive less often Microevolution Change in a population’s alleles over a period of time Macroevolution Large changes recorded in the fossil record (large scale) Speciation: When a group of one species is cut off from the rest of the population and gene flow is stopped. Each group is acted on by local selective conditions. Kiabab Squirrel Abert Squirrel Divergent Evolution – two groups of the same species separate and become less alike over time Video Convergent Evolution – two unrelated groups of organisms develop similar structures based on similar living conditions Gradualism • Evolution in slow gradual steps Punctuated Equilibrium • short periods of rapid species formation followed by long periods of little evolution Video Evidence Supporting Evolution 1. Fossil Record, p.299 • Types/examples of 2. Geographic Distribution, p.300 3. Similarities in Structure, p.301 • • Homologous structures Vestigial structures 4. Similarities in Development 5. Molecular Biology Any preserved remnant or impression left by organisms that lived in the past. Relative dating – superimposition of sedimentary rocks tells the relative age of fossils Absolute dating – dating using half-lives of radioactive isotopes (Potassium 40, Rubidium 87, Uranium 238, Carbon 14) Transitional forms – Archeoptryx and similar bird-like reptiles. Absence of some forms can also be used as an argument against evolution. Geographic Distribution Homologous structures Structures that share a common ancestry. Modified versions of the same structure. Vestigial structures Remnants of an organisms evolutionary past. The structure serves no major purpose at this time. Developmental Similarities Embryos start out looking very similar salamander, cow, pig, tortoise, fish, chicken, human rabbit The longer it takes into development to look different, the more closely relate the species DNA comparison - The longer that species or populations are separated, the more chance there is for mutations to cause differences in DNA Similar DNA = close relative (recent ancestor) Protein comparison - Similar to DNA comparison, but focuses on amino acid sequence in common proteins