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HAPPY MONDAY Today you will need: Notecards and your Journal Please have your Notecards or Late Video Homework out and ready to be checked! Bellwork for today: • On the left side of your notes: • Explain how Natural Selection works to change a population over time? • You must use these words: Traits, Offspring, Adaptation, Fitness, Environment • *Hint: Think about the bunny simulation from Friday Journals out… •Page:____ •Title: Mechanisms of Evolution •EQ: What are five factors that affect evolution? Standard B.7C - Analyze and evaluate how natural selection produces change in populations, not individuals. B.7E - Analyze and evaluate the relationship of natural selection to adaptation and to the development of diversity in and among species. I. Mechanisms of Evolution A quick Recap…. A gene pool is the total number of genes of every individual in an interbreeding population. Evolution can be defined as a change in the gene pool over time. There are 5 factors that can affect the frequency of a gene in the gene pool. 1. Small Population 2. Non-random Mating 3. Gene Mutations 4. Gene Flow 5. Natural Selection 1. Small Population a. Bottleneck effect- when a large portion of a population dies causing a significant decrease in the size of the gene pool. b. Founder effect- when a few individuals from a population leave and start another population in a different location. *Both examples will decrease the size of the gene pool in the new population. 2. Non-Random Mating 1. Not all mates are created equal. 2. In many species, mates are not selected at random. Many organisms compete for mating rites. Strong and goodlooking organisms are typically favored. 3. This limits the size of the gene pool because only the genes of the mating individuals are passed to the next generation. 3. Genetic Mutation 1. the source of all new genes in a gene pool and the ultimate source of new traits in a population 4. Gene Flow: the movement of genes into or out of a population. a. Emigration- individuals leave a population and decrease the size of the gene pool. b. Immigration- individuals from a different population enter a new population and begin breeding. This increases the size of the gene pool. Genetic Drift: change in a type of genes in a population due to a random occurrence. • Examples of Genetic Drift • Genetic drift refers to the change in a type of genes in a population due to a random occurrence. In other words, a random circumstance causes a certain genetic trait to become more common or rarer over time. Occurrences of Genetic Drift: • Genetic drift can be seen in these examples: • An exploding volcano destroys almost all of the most common trees on a small island. Over time, the types of tree that were not affected by the volcano continue to flourish, while the once-common tree’s population continues to dwindle. • Many individuals are killed due to a disease that only attacks those with blue eyes, causing blue eyes to become rarer in the area. 5. Natural Selection 1. survival of the fittest 2. advantageous genes are passed on to the next generation while harmful genes are eliminated 3. the driving force of evolution •How does the size of the gene pool affect the rate of evolution? Effects of Gene Pool Size 1. A decrease in gene pool size increases the speed of evolution. 2. An increase in gene pool size reduces the speed of evolution. Changes in the frequency of a gene in the gene pool initially leads to microevolution. Microevolution refers to a small change in a population over a short amount of time. Many small changes eventually lead to macroevolution. Macroevolution refers to the sum total of many changes that transform organisms over a long period of time. Macroevolution leads to speciation or the creation of a new species. When an evolving population can no longer interbreed with the original population, a new species is formed. Changes in the frequency of a gene in a gene pool leads to Microevolution: small change over a period of time leads to Macroevolution: total of many changes that transform organisms over a long period of time. leads to Speciation: creation of 2 different species from 1 original species Gene pools can change in 3 different ways: a. Disruptive selection b. Directional selection c. Stabilizing selection 1. Disruptive selection: individuals on the upper and lower ends of a distribution curve are more fit than organisms in the middle, curve becomes a U-shaped. 2. Directional selection: when organisms at one end of the distribution curve have the highest fitness, shifts the curve in one direction. 3. Stabilizing selection: when individuals in the middle of the distribution curve have the highest fitness, the curve does not move/change. Mix-Freeze-Group Genetic Mutation Natural Selection Small Population Non-Random Mating • I am going to survive! Because I have the best genes for my environment. • I am HUGELY affected by genetic drift. • I am VERY picky. I will only choose you, because your traits are most attractive to me. • I am a mistake in the DNA sequence