genetic equilibrium chapter 16- section 1. what is a population? a group of individuals of the same...
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Genetic Equilibrium
Chapter 16- Section 1
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What is a population?A group of individuals of the same species that routinely interbreed
Population Genetics – the study of evolution from a genetic point of view
Microevolution- the change in the collective genetic material of a population
Biston betularia f. typica is the white-bodied form of the peppered moth
Biston betularia f. carbonaria is the black-bodied form of the peppered moth.
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Variation of Traits within a population
Within a population, individuals will vary in observable traits
Ex. Fish of a single species in a pond will vary in size
Few fish are very short or very long
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Causes of variationVariations influenced by environmental factors
Ex. Amount or quality of food, sunlight, living space
Variations in genotype1. Mutation – a random change in a gene2. Recombination – reshuffling of genes in a diploid3. Random pairing of gametes – millions of sperm are produced, 1 gets to fuse with egg
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The Gene PoolA population’s gene poolgene pool is the total of all genes in the population at any one time.
• If all members of a population are homozygous for a particular allele, then the allele is fixed in the gene pool.
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The Hardy-Weinberg The Hardy-Weinberg TheoremTheoremUsed to describe a non-evolving populationnon-evolving population..
Natural populations are NOT expected to actually be in Hardy-Weinberg equilibrium
Deviation from Hardy-Weinberg equilibrium results in evolution
Understanding a non-evolving population, helps us to understand how evolution occurs
*Genotype frequencies in a population tend to remain the same from generation to generation unless acted on by an outside source
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Conditions of the H-W Conditions of the H-W TheoremTheorem
1.Large population size - small populations can have chance fluctuations in allele frequencies (e.g., fire, storm).
2.No migration- immigrants can change the frequency of an allele by bringing in new alleles to a population.
3.No net mutations- if alleles change from one to another, this will change the frequency of those alleles
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Conditions of the H-W Conditions of the H-W TheoremTheorem
3.Random mating- if certain traits are more desirable, then individuals with those traits will be selected and this will not allow for random mixing of alleles.
4.No natural selection- if some individuals survive and reproduce at a higher rate than others, then their offspring will carry those genes and the frequency will change for the next generation.
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•Hardy-Weinberg Equilibrium The gene pool of a non-evolving population remains constant over multiple generations; i.e., the allele frequency does not change over generations of time. •The Hardy-Weinberg Equation: 1.0 = p2 + 2pq + q2
where p2 = frequency of AA genotype; 2pq = frequency of Aa plus aA genotype; q2 = frequency of aa genotype
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Hardy-Weinberg Equilibrium
Population of cats n=10016 white and 84 blackbb = whiteB_ = black
Can we figure out the Allele frequencies of individuals BB and Bb?