1/1/12Tenets of the theory of Natural Selection1. 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 reproduce3. Environment determines which traits are favorable4. Traits are heritable (favorable traits can and will contribute to next generation)5. Over time, favorable traits accumulate in a population Leads to new species6. Geographic (or some other form) isolation is important- - Darwin’s Evidence for NS o Homologous Structure Characteristics that species share because of a common ancestor- Most mammals have 5 digitso Vestigial Structures 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 functionalo Embryology All embryos early in development look VERY similaro Geography 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 GalapagosArtifical Selection vs. Natural Selection Implies a “maker” NaturalTakes place over short period of time Thousands of yearsRole of environment is hidden Environment is stimulationGoal in mind Adaptation, natural- Natural Selection o The genetic change(s) in a population over time due to DNRS of individualso Differential Net Reproductive Success – The number of offspring that you have, that you raise to reproductive age (fitness)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 CHANGEo 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 Wallaceo Wallace: NS accounts for all traits in organismso Darwin: NS important BUT sexual selection changes things Sexual Selection – Doesn’t sacrifice losers and is not environmentally based. Traits are chosen by one sex (humans are unique) Sexual Dimorphism – differences in males and
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