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Essential Question: What mechanisms have allowed for diversity in organisms? NATURAL SELECTION.

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Presentation on theme: "Essential Question: What mechanisms have allowed for diversity in organisms? NATURAL SELECTION."— Presentation transcript:

1 Essential Question: What mechanisms have allowed for diversity in organisms? NATURAL SELECTION

2 BREEDING BUNNIES In this investigation you will examine natural selection and genetic drift in a small population of wild rabbits.

3 Hypothesis: Record a hypothesis for how natural selection affects gene frequency in the population of wild rabbits over several generations. BREEDING BUNNIES

4 Predict : State what you would predict (if your hypothesis is supported) about the frequency of G alleles and g alleles in the population of rabbits after 10 generations, where gg bunnies are selected against (do not survive). BREEDING BUNNIES

5 BREEDING BUNNIES – DATA ANALYSIS How do you calculate the frequency of alleles? Frequency of G = G/ total # of alleles Frequency of g = g/ total # of alleles The sum of the frequencies should = 1

6 BREEDING BUNNIES – DATA ANALYSIS # of generations Frequency of allele Frequency of Alleles in a Population of Wild Rabbits over 10 Generations

7 1.Was your original hypothesis supported by the data? Explain. 2.How does the number and frequency of alleles for the dominant characteristic compare with the number of alleles for the recessive characteristic? 3.The change in the frequency of alleles is called genetic drift. Why is genetic drift more likely to occur in smaller populations? 4.Why does genetic drift occur in the first place? BREEDING BUNNIES – ANALYSIS

8 5.In a real rabbit habitat new animals often come into the habitat (immigrate), and others leave the area (emigrate). How might emigration and immigration affect the gene frequency of G and g in this population of rabbits? 6.How could you simulate migration if you were to repeat this activity? 7.How do your results compare with the class data? If different, why are they different? BREEDING BUNNIES – ANALYSIS

9 8.How are the results of this simulation an example of evolution? 9.What are the key components of natural selection? 10.What kinds of limited resources can create a struggle between individuals in a population? 11. What kinds of variable traits (other than fur or lack of) within a population might natural selection act upon? 12. How does natural selection affect the genetic variation within the next generation of the same population? BREEDING BUNNIES – ANALYSIS

10 WHAT IS EVOLUTION? Change in Gene Frequencies over time due to random processes (Refined definiton) Mechanisms of Evolution Genetic drift Gene flow Mutation Natural selection

11 MECHANISMS FOR EVOLUTION – GENETIC DRIFT Can be independent of natural selection May result in decrease in genetic diversity Founder effect – Blue Fugates of Kentucky Bottleneck effect – FL Panthers

12 MECHANISMS FOR EVOLUTION – GENE FLOW Migration Immigration – moving into a population Emigration – moving out of a population Increase in gene flow between 2 populations can lead to having more similarities between populaitons – less diversity Decrease in gene flow can lead to speciation

13 Changes in the structure of genes and chromosomes The origin of all new alleles Increases variations Make extinction less likely Mostly random events MECHANISMS FOR EVOLUTION – MUTATIONS

14 MECHANISMS FOR EVOLUTION - NATURAL SELECTION Four requirements for natural selection to occur Organisms produce more offspring than can survive heritable Organisms have heritable traits Limited resources leads to a struggle for existence Organisms having traits that are better suited for a particular environment are more likely to survive and reproduce

15 SURVIVAL OF THE FITTEST - WHAT IS FITNESS? Biggest? Fastest? Strongest? Prettiest? Furriest? NO!

16 ?!

17 SURVIVAL OF THE FITTEST – QUICK WRITE Why is the phrase “survival of the fittest” a misrepresentation of Darwin’s concept of evolutionary fitness?


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