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Download Intro To Evolutionary Process
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Intro to Evolution Typically divided into 2 areas of study… • Microevolution-the actual processes that allow genetic diversity to occur • Macroevolution-measuring the success of the changed genes HMS Beagle Bio-geographical Isolation! Darwin’s 5 Key Observations: 1) Species have great fertility 2) Populations remain roughly the same size (with a stable environment!!) 3) Resources are limited These mean there is a struggle for survival among individuals. 4) Variation is rampant. 5) Variation is heritable. What evolution is… • Evolutionary process deals with any biological processes that changes the gene sequence for a trait. • Individuals express changes but populations evolve! What evolution is not… • Changes in non-living things. • Changes in individuals • Microevolution is the actual change in genes • Macroevolution is the environmental pressures that select fittest organisms Now that we have established what evolution is, how do we get genes to change? There are 5 mechanisms that result in a change in genes and new alleles to form…. 1. Mutations- missense mutations are point level changes in the DNA. A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations. 2. Crossing Over- causes changes in gene sequencing which can change phenotype. 3. Gene flow is any movement of genes from one population of like organisms to another. (emigration and immigration) • Gene flow occurs when individuals join new populations and reproduce. • This can introduce new alleles from neighboring populations. • Sometimes gene flow keeps neighboring populations similar. • Gene flow decreases the chance that two populations will evolve into different species. bald eagle migration 4. Sexual reproduction Which egg and which sperm? 5. Genetic Drift – in each generation, some individuals may, just by chance, leave behind a few more. The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better” individuals. – This causes a decrease the in the number of alleles, rather than adding something new. Two types of genetic drift: Founder Effect Bottleneck Founder effect is a type of genetic drift. – It occurs when a few individuals start a new population. – The diversity is decreased in the founded population. Bottleneck is another type of genetic drift. – It occurs when an event drastically reduces population size. – The bottleneck effect is genetic drift that occurs after a bottleneck event Genetic drift has negative effects on a population. – less likely to have some individuals that can adapt – harmful alleles can become more common due to chance rather than the ability of the survivor. The occurrence of evolutionary process is random, but the results are not We can’t control the 5 mechanisms of gene change, but the drive to produce “better” offspring outweighs any possible negative outcomes. Think about it like this: • Genes are shuffled up using the 5 mechanisms of evolution. (Random) • Each sibling will be genetically unique • The parents do not know what new combination their offspring are getting • Winners are determined by nature’s specific set of rules (non-random)