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Unit V:Population Genetics (Hardy Weinberg Equilibrium) Ms. Buechler Int. Sci. 4/Biology.

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Presentation on theme: "Unit V:Population Genetics (Hardy Weinberg Equilibrium) Ms. Buechler Int. Sci. 4/Biology."— Presentation transcript:

1 Unit V:Population Genetics (Hardy Weinberg Equilibrium) Ms. Buechler Int. Sci. 4/Biology

2 EW5/7 Q: In the “Zonkeys” reading you were asked if hybrids help or hurt the “gene pool”… what’s a gene pool? Genetic Diversity is a good thing!

3 Population Genetics Vocabulary Population = members of the same species that share a habitat Fitness =how good a particular genotype is at leaving offspring in the next generation relative to how good other genotypes are at it ◦ Depends on the environment Allele frequency= how often a specific allele for a trait appears in a population Gene Pool = the total number of genes in an interbreeding population ◦ The greater # of genes in a population the more genetic diversity  Increases the “fitness” of the population in the environment ◦ Reduces the chance of extinction  increases survival rate in the population

4 Hardy-Weinberg Equilibrium Genetic variation introduced by the processes of meiosis (crossing over) and random fertilization does not, itself, alter a population’s overall gene pool. The frequencies of alleles in a population’s gene pool will remain constant indefinitely (i.e. will be in equilibrium) unless a “disturbing” influence is introduced. A theoretical non-evolving population is said to be in Hardy-Weinberg equilibrium.

5 When does evolution occur? Evolution occurs when populations deviate from the Hardy-Weinberg equilibrium. The mechanisms that drive evolution are: ◦ Natural Selection ◦ Sexual Selection ◦ Mutation ◦ Genetic drift ◦ Gene Flow

6 Natural Selection Natural Selection = selective pressures causing a change in allele frequency. ◦ Heritable phenotypes that cause an advantage in the population’s fitness become more common in a population.

7 Sexual Selection Sexual Selection = the more attractive members of a population are more likely to mate and pass on their genes ◦ Non-random mating occurs ◦ This changes the allele frequency as the “more attractive” members of the population pass on more alleles than the “non- attractive” members Male Elephant seals fight for the right to breed with ALL the females in the colony

8 Mutations Mutation = is a random permanent change in an organism’s DNA. Heritable mutations can lead to changes in the gene pool of a population. New mutations can be: ◦ harmful ◦ neutral ◦ advantageous Due to their lack of camouflage, albino alligators generally do not survive to adulthood in the wild.

9 Genetic Drift Genetic Drift= Population change due to random changes in genotypic frequencies. ◦ The smaller the population, the greater the effect of genetic drift on the population’s gene pool. EX> Suppose a natural disaster randomly kills a large portion of the population; ◦ the remaining survivors may have allele frequencies that were very different from the previous population

10 Gene Flow Gene Flow = Transfer of genes from one population to another of the same species ◦ Migration/ Immigration ◦ Seed/pollen/larv a dispersal Changes allele frequency ◦ New alleles can be introduced into a population or alleles can be removed from a population.

11 Migration Migration into or out of a population can cause deviations from Hardy-Weinberg expectations. ◦ New alleles can be introduced into a population or alleles can be removed from a population. ◦ The frequencies of alleles and genotypes in a population can be altered. The arctic tern migrates longer distances than any other known bird.

12 Videos Crash Course: Population Genetics Bill Nye: Biodiversity

13 Prep for Vocab Quizzes M 5/12 Vocab 5 Mutation Genetic Recombination /Crossing Over Phylogenetic Species Concept Morphology Natural selection Evolution Extinction Camouflage Claim Evidence Vocab 6 Adaptation Classify Common Ancestor Extinction Fitness Natural Selection Sexual Selection Speciation Species

14 Prep for Benchmark & Unit Exam Benchmark 5 on T 5/13 Use Firefox eLearning BM Testing/EOC Select Benchmark #5 2 Free Response ◦ One of those is a conclusion question 25 MC or T/F Questions Score a 3.5 or higher and you are excused from the unit exam Unit V Exam on Th 5/15 18 total matching (in two sections) over Evolution Key Terms and Classification Key Terms. 27 MC questions

15 Good Sources of Review of Classification/Evolution Exam Study Guide Unit V http://apesnature.hom html http://apesnature.hom html http://www.biology- al_selection.htm http://www.biology- al_selection.htm http://www.visionlear ule_viewer.php?mid=6 8&l http://www.visionlear ule_viewer.php?mid=6 8&l http://www.bio200.bu lature.html http://www.bio200.bu lature.html http://learn.genetics.u ion/sources/ http://learn.genetics.u ion/sources/

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