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Bellringer Please get out your lab and Notes. complete the questions on the lab. NO COPYING. Population Genetics The study of genetic traits and changes in populations. Population Genetics 1. Gene pool The combined genetic information of all the members of a particular population. Population Genetics 2. Allele frequency Is the number of times that an allele occurs in a gene pool compared with the number of times other alleles occur (ex. beans and bunnies lab). Population Genetics 3. Genetic equilibrium Allele frequencies remain constant. ►Is this even possible in a changing environment?...... Population Genetics 5 Conditions to maintain genetic equilibrium 1. Random mating 2. Population must be very large 3. No immigration/emigration 4. No mutations 5. No natural selection! Therefore, if the gene frequency of a population changes then it must have “evolved”! Mechanisms of Evolution Mechanisms of Evolution There are several: 1. Natural Selection 2. Gene Flow 3. Genetic drift 4. Mutations 5. Non-random mating 1. Natural Selection .Nature decides .Populations, not individuals, evolve 1. Natural Selection: . Affects variation in a population as the better adapted (more fit) individuals survive and reproduce, passing on their genes to the successive generations. Acts only upon an organisms phenotype. If the phenotype is better suited for a changing environment, the individual can survive and pass on its genes. Natural Selection 6. Gene Flow Transport of genes by migrating individuals . New genes in a population by means other than mutations. EX: migration of birds. Gene Flow 5. Genetic Drift Change in the gene pool that takes place strictly by chance. .Affects small populations .Increases the chance of rare alleles EX: shipwreck survivors colonizing an island Examples of Genetic Drift . A) The Founder Effect: . Small population that branches off from a larger one may or may not be genetically representative of the larger population from which it was derived. Only a fraction of the total genetic diversity of the original gene pool is represented in these few individuals. Examples of Genetic Drift . B) Population Bottleneck: . Occurs when a population undergoes an event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing. •The event may eliminate alleles entirely or also cause other alleles to be over- represented in a gene pool. EX. Cheetahs 4. Mutations . Causes genetic change . Can occur by chance . Many are lethal . Quickly eliminated . Some are useful . Become part of gene pool by the process of natural selection 5. Non-Random Mating . In animals, non-random mating can change allele frequencies as the choice of mates is often an important part of behaviour. Many plants self-pollinate, which is also a form of non- random mating (inbreeding). Charles Darwin’s finches.

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Evolution by Natural Selection, Formulated Independently by Charles Darwin and Alfred Russel Wallace
UNIT 4 EVOLUTIONARY PATT EVOLUTIONARY E RNS AND PROC E SS E Evolution by Natural S 22 Selection Natural selection In this chapter you will learn that explains how Evolution is one of the most populations become important ideas in modern biology well suited to their environments over time. The shape and by reviewing by asking by applying coloration of leafy sea The rise of What is the evidence for evolution? Evolution in action: dragons (a fish closely evolutionary thought two case studies related to seahorses) 22.1 22.4 are heritable traits that with regard to help them to hide from predators. The pattern of evolution: The process of species have changed evolution by natural and are related 22.2 selection 22.3 keeping in mind Common myths about natural selection and adaptation 22.5 his chapter is about one of the great ideas in science: the theory of evolution by natural selection, formulated independently by Charles Darwin and Alfred Russel Wallace. The theory explains how T populations—individuals of the same species that live in the same area at the same time—have come to be adapted to environments ranging from arctic tundra to tropical wet forest. It revealed one of the five key attributes of life: Populations of organisms evolve. In other words, the heritable characteris- This chapter is part of the tics of populations change over time (Chapter 1). Big Picture. See how on Evolution by natural selection is one of the best supported and most important theories in the history pages 516–517. of scientific research.
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NOTES – CH 17 – Evolution of Populations
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