1 1 12 Tenets of the theory of Natural Selection 1 All species must be able to reproduce faster than the food supply increases the struggle for existence 2 The individuals with the more favorable traits are more likely to reproduce 3 Environment determines which traits are favorable 4 Traits are heritable favorable traits can and will contribute to next generation 5 Over time favorable traits accumulate in a population Leads to new species 6 Geographic or some other form isolation is important Darwin s Evidence for NS o Homologous Structure o Vestigial Structures Characteristics that species share because of a common ancestor Most mammals have 5 digits o Embryology o Geography Structures that organisms have that are not adaptations to their environment but to their ancestor s environments Whales have a pelvis and hind leg bones that are internal and not functional All embryos early in development look VERY similar South American Mainland Galapagos Also went to Camp Verde islands and African Mainlands Verde and Galapagos are very similar if Fixity of Species were true they would have the same animals In the end African animals were similar to Verde and South American animals were similar to Galapagos Artifical Selection vs Natural Selection Implies a maker Takes place over short period of time Role of environment is hidden Goal in mind Natural Selection Natural Thousands of years Environment is stimulation Adaptation natural o The genetic change s in a population over time due to DNRS of individuals o Differential Net Reproductive Success raise to reproductive age fitness The number of offspring that you have that you o One does not evolve the population or species does Natural Selection acts on the individual Natural Selection in action through camouflage Peppered moths have normal variation in color Birds are natural predators When grey lichen was on trees All moths grey Industrial revolution Lichen dies Black trees Black moths Pollution cleaned up grey moths returned ENVIRONMENT STIMULATES CHANGE o Insights from NS Trait must be inherited for it to be important in NS Must be variation in the trait for NS to act Fitness of the organism is relative to the environment Differences between Darwin and Wallace o Wallace NS accounts for all traits in organisms o Darwin NS important BUT sexual selection changes things Doesn t sacrifice losers and is not environmentally based Sexual Selection Traits are chosen by one sex humans are unique Sexual Dimorphism differences in males and females
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