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Evolution.notebook May 12, 2011 Evolution process of change over time Theory of Evolution existing forms of life on earth have evolved from earlier forms over long periods of time Evidence of Evolution: 1. Geological Record shows earth is 5 billion years old 2. Fossils remains or traces of organisms that no longer exist * Age of fossils determined by dating of the rocks in which it is found * Found preserved in ice, tar, amber * Formed by petrification process where tissues are replaced by minerals that make it turn stonelike. * Fossils found in lower strata (layer) older and simpler * Fossils found in upper strata younger and more complex 1 Evolution.notebook * Resemblances exist between layers of strata possible link between modern and primitive species * If no resemblances organisms die out May 12, 2011 3. comparative anatomystudy similarities in structure of related organisms a. homologous structuresbody parts similar in structure even though their function may differ, suggest common ancestry ex. Bone structure in a whale's flipper, forearm of a human, and wing of a bat b. Purpose of homologous structures: suggests a common ancestor Analogous Structures: same function; different structure Example: bird and insect wing 2 Evolution.notebook May 12, 2011 Vestigial Structures: nonfunctional structures that are remnants of structures that were functional in ancestors Example: tailbone remnant reptilian tail appendix remnant digestive sac fly does not have bones in its wing 4. Comparative Embryology: comparison of early stages of development Purpose: if embryos of different species are very similar, it suggests a common ancestry 3 Evolution.notebook May 12, 2011 5. Comparative Cytology cell organelles are compared between organisms 6. Comparative Biochemistry structure and function of DNA, RNA, proteins, enzymes are similar in closely related organisms Example: Organism # of amino acid differences Chimp Cow Frog 0 10 20 THEORIES OF EVOLUTION 1. Lamark Evolution has 2 principles a. Law of Use and Disuse the more you use a body part, the stronger it becomes b. Inheritance of Acquired Characteristics organisms develop characteristics by use/disuse and pass them on to their offspring 4 Evolution.notebook May 12, 2011 Disproved by Weismann * cut off tails of mice for 22 generations * In each generation, mice were always born with tails * So, acquired characteristic of no tails was not inherited. Charles Darwin 2. Darwin best known theory based on presence of variations among members of a species and natural selection d. Adaptation any kind of inherited trait that improves an organism's chance for survival a. overpopulation too many offspring produced in an area e. Survival of the Fittest only the "best fit" organisms survive and reproduce because of their adaptations and variations b. competition resources are limited c. variation different characteristics of the organisms in a species. Comes from: * meiosis/sexual reproduction * random gene & chromosome mutations f. Natural Selection the environment determines which adaptations and variations are helpful or harmful. Nature selects which organisms survive. * thick fur helpful in cold * thin fur harmful in cold 5 Evolution.notebook g. Reproduction organisms with helpful variations tend to survive and reproduce, passing on variations to their offspring May 12, 2011 http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html h. Speciation development of a new species will occur as variations accumulate in a population over time 1. Industrial Melanism - development of dark colored organisms in a population exposed to industrial air pollution Example: peppered moth in England * before 1850 - moth was light colored, a few were black * 1850-1900 - heavy industrialization causes smoke to darken trees *After 1900 - moths are black * In non-industrialized areas, light colored moths continue to predominate WHY DID THIS CHANGE OCCUR??? Dark gene was already in population 6 Evolution.notebook May 12, 2011 2. Bacterial Resistance to Antibiotics 3. Insect Resistance to DDT • Antibiotics usually kill bacteria • Once antibiotics became common, resistant strains of bacteria began to appear • Antibiotics were no longer effective in killing those strains • DDT - insect spray • Some insects have a natural resistance (genetic) to DDT • When DDT-sensitive insects were killed by spraying, the DDT-resistant insects survived & passed on their natural DDT resistance to their offspring WHY?????? Modern Theory of Evolution includes both Darwin's ideas of variation and natural selection and the genetic basis of variations in populations. Change in gene frequency over time. 2. Reproductive Isolation * In time, organism will evolve into a new species * Isolated population will eventually become so different that they cannot interbreed even if barrier is removed. Factors that cause speciation: 1. Geographic isolation * Changes in genes that lead to a new species are more likely to occur in smaller populations * These populations can be segregated by a geographic barrier (water, mountains...) Environment is the major cause for adaptations! Types of Adaptations: 1. Structure involve physical body of organism (wings, fins, legs...) 2. Physiology involve metabolism of organism (poison venom of snake, spider web) 7 Evolution.notebook May 12, 2011 3. Behavior - involve actions of organism (mating, migration, hibernation) * Warning Coloration - colors of animal make it obvious to predators due to nasty taste. Predator learns its lesson after one bite. 4. Protection * Camoflauge - blend into background (flounder, fawn, chameleon) Monarch butterfly * Mimicry - one organism is protected from predator by its resemblance to another species Snake Mimicry http://chalk.richmond.edu/education/projects/webunits/adaptations/snake.html Monarch butterfly Viceroy butterfly Time Frame for Evolution: 1. Gradualism - evolutionary change occurs slowly, gradually, and continually. Small variations accumulate and cause reproductive isolation and a new species 2. Punctuated Equilibrium: species have long periods of stability interrupted by geologically brief periods where major changes occur possibly leading to the evolution of a new species 8 Evolution.notebook May 12, 2011 Heterotroph Hypothesis 1st life forms on earth were heterotrophs and had to obtain nutrients from the environment * Supported by the Miller/Urey experiment * devised apparatus and simulated conditions of primitive earth * showed that in the presence of heat & electrical energy, gases could combine to form simple organic compounds * Primitive Earth's atmosphere *No free oxygen. Only H2, NH3, CH4, & H2O vapor gases *hot, lightning, UV light, radiation from rocks * 1st precell simple molecules > complex molecules > clusters > heterotrophic cells (anaerobic respiration) * Rise of photosynthesis anaerobic respiration resulted in buildup of CO2 in atmosphere. Some heterotrophic cells adapted to use CO2 to make organic compounds. These heterotrophic cells became the 1st autotrophs (plants). O2 was then produced. 9 Evolution.notebook May 12, 2011 10