Chapter 23 - Evolutionary Mechanisms

Chapter 23 - Evolutionary Mechanisms - Evolutionary...

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Evolutionary Mechanisms Read: CH 23 454-471 Genomic Imprinting Where either male or female had an effect and silenced opposite sex allele. If one chromosome comes from one parent, second from the other, that allele will cause silencing. Pretty rare, doesn’t occur very often. Check notes for disease caused by GI. Evolution of Population Individuals DO NOT evolve; populations evolve. Natural selection acts on individuals, but they do not evolve. Stronger wolf may produce more offspring than weaker wolf, but stronger wolf doesn’t evolve. Evolution – Change in allele frequencies over time. Read for nitty gritty details 2 Types of Evolution Microevolution – evolutionary change on the smallest scale. Changed observed in genetic makeup of a population from one generation to the next. Relatively small amount of change in a short time. Allele frequency changes. Evolution below the species level Macroevolution – Evolution above the species level. Major evolutionary developments – feathers, flight, eyes, flippers, fins, radius/ulna example. Microevolution – 2 parents produce descendent. Crossing over occurs, other Mendelian genetics going on. Each parent may have same or different allele frequency they’re passing on. Macroevolution – Not just looking at population. Speciation occurs – origin of new species. Focal point of evolution. Not enough to explain how adaptations evolve in populations. 2 Types of Macroevolution Anagenesis – Accumulation of heritable changes altering the characteristics of a species. Species A gives rise to Species B. Probably same genus name. Lowest level of macroevolution possible. Not showing what the change is. Cladogenesis – Branching evolution in which new species arises from population that buds/branches from parent species. Parent species may also evolve. Microevolution - Within Species, mating, populations interact, within species genetic variation. Macroevolution – Species no longer mating together, new species created.
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Chapter 23 - Evolutionary Mechanisms - Evolutionary...

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