Presentation on theme: "Chapter 16 Population Genetics and Speciation"— Presentation transcript:
1 Chapter 16 Population Genetics and Speciation 16-1 Genetic Equilibrium
2 Terms to KnowPopulation genetics – study of evolution from a genetic point of viewMicroevolution – evolution at the genetic levelBell Curve – most members of the population have similar traits; only a few are at the extremesCan SHIFT over time!!!
4 Variations of Traits Within a Population Causes of VariationMutationsTAGATC -> TAAATCRecombination (crossing-over and independent assortment)(during meiosis)3. Random pairing of gametes-which sex cells combine successfully
5 The Gene PoolGene pool = the total genetic information available in a populationAllele Frequency = number of a certain allele / total number of alleles in a populationCalculated by … # of allele Btotal # of B and b
6 What is the allele frequency? Half a population of four o clocks are red/ half are white.What is the frequency of the r allele?0.50 or 50%
7 The Gene PoolPhenotype Frequency = # of individuals with a phenotype / total # of individuals within the population# red flowers/ Total # of individualsvideo
8 Hardy – Weinberg Genetic Equilibrium Ideal hypothetical population that is not evolving (not changing over time)5 criteria (must be met)No net mutations occurNo one enters or leaves the populationThe population is largeIndividuals mate randomlySelection does not occurWhy might a population never be in HW genetic equilibrium???
10 MutationGene flow – the ability of genes (alleles) to be shared among members of a species (immigration and emigration)3. Genetic Drift – change in allele frequencies due to chance, usually because the population is smallWhen gene flow stops, the 2 populations might now become separate species (Ex. Dogs and wolves) Speciation in progress.
11 4. Nonrandom mating – mate selection is influenced by geographic proximity, mates with similar traits, and sexual selection
12 - stabilizing selection - disruptive selection - directional selection 5. Natural Selection – some members are more likely to survive and reproduce- stabilizing selection- disruptive selection- directional selection
13 Types of SelectionStabilizing selection - individuals with average forms of a trait have the highest fitnessEx. Large lizards will be spotted by predators; small lizards can’t run fast enough to get away from predators
14 Types of SelectionDisruptive Selection – individuals with either extreme of the trait has the greatest fitnessEx. White moths on white trees cannot be seen; Dark moths on dark trees cannot be seen; medium colored moths will be seen on both trees (eaten by birds)
15 Types of SelectionDirectional selection – more extreme form of a trait has the greatest fitnessEx. Anteaters with the longest tongues will get the most food
19 The Concept of Species Speciation – the process of species formation Morphology – internal and external appearance of an organismSpecies – morphologically similar and can interbreed to produce fully fertile offspring
20 Morphological vs Biological Species Concept 2 competing concepts (ideas) on how to determine different speciesMorph = based solely on appearanceBio = based on who can reproduce with who successfully (not useful for extinct or asexual organisms)What do we use today?Mix of BOTH!!!
21 Isolation and Speciation Geographic isolation – physical separation of members of a speciesEx. River dries up into several small pools; fish diverged enough to be considered separate species