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Texas State - BIO 4301 - Study Guide - Midterm

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Texas State - BIO 4301 - Study Guide - Midterm

School: Texas State University
Department: OTHER
Course: Evolution
Professor: James Ott
Term: Spring 2017
Tags:
Name: BIO 4301 Study Guide 2
Description: This study guide will help prepare you for exam 2
Uploaded: 10/21/2017
0 5 3 87 Reviews
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background image Evolution Exam 2   Gene Flow   •  Occurs because individuals move into (or out of) a population bringing 
either 
New alleles not present in that population, or  Immigrants bring in alleles with different frequencies   •  Results from dispersal   •  Is measurable  Δ p = m(p m -p)  M = migration rate  P = allele frequency in migrants  P = frequency of recipient population  If 100 individuals out of 1000 are immigrants, m = 0.1  •  Makes populations become more similar   •  Effects on populations:  Increases genetic variation (in new populations)  Makes populations more genetically similar   **Genetic drift has the opposite effect; fixing for different alleles**     Natural selection makes populations different from each other. Why?  •  Populations occur in different environments   •  Traits selected for in one population aren't the same for those selected in 
other populations 
If both drift and selection make populations similar, what happens?  •  Depends on gene flow and population size 
background image •  If one migrant per generation or more, population will look like source 
populations 
•  Migration rate proportion increases in small populations counteracts 
greater loss of variation 
•  If less than one migration per generation, population will diverge       Measuring Population Divergence   •  F = inbreeding  Reduces genetic variation  •  Genetic variation can be measured by heterozygosity   •  F ST  = reduction in heterozygosity in subpopulations compared to total  population in which they are a part     Measures of Genetic Diversity  •  Heterozygosity: proportion of loci that carry two different alleles at a 
single locus within an individual  
As genetic diversity increases, heterozygosity increases  •  Individual Level: organisms that are heterozygous across multiple loci are 
more fit than homozygous organisms 
•  Within Population: allows for adaptive responses to environmental 
heterogeneity and environmental change 
•  Among Population: reflects importance of local adaptation   **Heterozygosity decreases as population size decreases**  •  Endangered species have reduced heterozygosity relative to similar non-
endangered relatives  
background image   Genetic Structure: genetic differentiation/spatial distribution of genetic variation  •  In fragmented populations, evolution happens    Consequences of Genetic Diversity  •  Loss of heterozygosity   •  Increased genetic divergence between populations  •  Effects more pronounced in small populations    F ST  = (H T -H S )/H   •  H S  = average heterozygosity of subpopulations   •  H T  = expected heterozygosity of total population          
background image   Population Divergence Example    Mexican  Puerto Rican  African American  Average Allele 
Frequency 
      Average 
Subpopulation 
Heterozygosity 
      Total heterozygosity        F ST =(H T -H S )/H T                          
background image Isolation by Distance: refers to the accrual of local genetic variation under 
geographically limited dispersal  
•  Results in (detectable) population differentiation  Not all population structure is reflected by geographic isolation     **As geographic distance increases, F ST  increases**  **As fragmentation increases, F ST  increases**   Both of these are reflective of isolation       Quantitative Traits & Estimating Heritability    Quantitative Trait: some measurable aspect of an organism  Darwin – evolution is continuous and gradual  Mendel – incompatible with gradualism   Polygenic Traits: traits for which the phenotype depends on alleles on many 
different genes 
Quantitative Theory: most traits are polygenic (multiple genes, small effects)    Evolution occurs only if:   •  Genetic variation exists  •  Natural selection, genetic drift, and gene flow affect amount of genetic 
variation in a population in different ways 

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School: Texas State University
Department: OTHER
Course: Evolution
Professor: James Ott
Term: Spring 2017
Tags:
Name: BIO 4301 Study Guide 2
Description: This study guide will help prepare you for exam 2
Uploaded: 10/21/2017
23 Pages 71 Views 56 Unlocks
  • Better Grades Guarantee
  • 24/7 Homework help
  • Notes, Study Guides, Flashcards + More!
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