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15.1 Theory of Natural Selection Darwin's Theory of Natural Selection Section 15.1 Variation: Are these people different? Darwin's Voyage · HMS Beagle England to South America · read Lyell's Principles of Geology · ashore he found lots of evidence supporting Lyell's ideas · variations and adaptations Natural Variation · physical differences among individuals · 2 types interspecific - members of different species intraspecific - members of same species · especially noticeable on Galapagos Islands Adaptation · noticed that animals seemed well suited for their environment 15.1 Theory of Natural Selection 1 What did Darwin notice about organisms during his voyage? A adaptations B variations C consistency D mutations Fossil and Geologic Evidence · found fossil remains that were similar to modern day organisms suggested that modern organisms are related to past life forms ex. Glyptodon and armadillo · found shells high in the Andes Mtn. how did water-dependent organisms get there? · experienced an earthquake that caused underwater land to rise above sea level · observations supported Lyell's theory Earth older than 6,000 years Earth gradually changing over time · Could organisms be changing gradually, too? Darwin Update · 5 year journey observations, collected specimen, experienced geologic events conclusion: change (evolution) happens · How does evolution happen? 20 years gathering more information in England studied work of farmers and breeders Artificial Selection · Darwin noticed variations in domesticated plants and animals that were NOT present in their wild relatives · artificial selection - process of humans changing a species by breeding it for certain desirable traits humans decided what is "useful" dog breeds, race horses, seedless fruit 2 Which of the following did not suggest to Darwin that change (evolution) happens? A Charles Lyell's Principles of Geology B fossil evidence C changes in global climate D natural variations and adaptations Heritability · Darwin started breeding pigeons experimented with certain traits · for artificial (or natural) selection to work, traits must have heritability traits can be passed from one generation to the next · disproved that species had not changed since the beginning of the Earth Victoria Crowned Pigeon 15.1 Theory of Natural Selection Natural Selection · individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals · environment decides what is "useful" selected traits gave individuals advantages in their environment 3 In natural selection, ____ determines what is useful. A random mutation B people C your mom D the environment Struggle for Survival · Thomas Malthus economist limited resources and disease keep populations in check · Darwin reasoned the same struggle took place in nature "Descent with Modification" · population - all the individuals of a species that live in an area · some individuals in a population had variations that made them well suited to their environment · adaptations arose over many generations..."descent with modification" organisms compete for food, living space, mates, etc. Alfred Wallace · English naturalist · developed a theory similar to Darwin's · wrote a letter to Darwin to complete the publish The Origin of Species by Means of Natural Selection (1859) 4 The notion that adaptations arise over several generations is called A survival of the fittest B descent with modification C natural selection D adaptive radiation 15.1 Theory of Natural Selection 4 Principles of Natural Selection · variation heritable differences basis of natural selection · overproduction lots of offspring increases the chances that some will survive creates competition for resources · adaptation certain variations allow an individual to survive better "naturally selected" live longer and have more offspring that share those adaptations · descent with modification over time, natural selection will results in species with adaptations well suited for survival and reproduction 5 What are Darwin's 4 principles of natural selection? A organisms adapt to their environment B over-reproduction lead to competition C variation exists in populations D each generation is slightly different than the one before it Existing Variation · acts on phenotypes NOT genotypes · traits in a population become favorable for survival b/c of a change in the environment n.s. acts on traits that ALREADY exist · new alleles occur through genetic mutation