AP Biology Evolution Review Slides

Transcription

1 AP Biology Evolution Review Slides

2 How would one go about studying the evolution of a tetrapod limb from a fish s fin?

3 Compare limb/fin structure of existing related species of fish to tetrapods Figure out the age of rock where the transition from fin to limb occurred Find the locations on Earth where this aged rock layer is at the surface Travel to these areas and search for a transitional fossil

4 Transitional Fossil: Tiktaalik This transitional fossil has characteristics of both fish and tetrapods

5 1. What are two differences you notice in the images between marine and freshwater sticklebacks? 2. What is the genetic mechanism between these differences? 3. What is a possible explanation for the reason that these differences exist? 4. If these characteristics change in a population over time, what could account for these changes?

6 1. What are two differences you notice in the images between marine and freshwater sticklebacks? Pelvic spines in the marine, absence in the freshwater and heavily plated body (gray areas in the images) in the marine versus far less plating in the freshwater. 2. What is the genetic mechanism between these differences? Mutations resulting in different alleles of protein coding genes and/or mutations resulting in changes in enhancer regions. 3. What is a possible explanation for the reason that these differences exist? Different selective environments: in the marine environment, the plating and spines may serve as protection against larger predators, but in the freshwater environment these same features might reduce fitness. 4. If these characteristics change in a population over time, what could account for these changes? An environmental change could result in different selective pressures and thus drive a change in a population s phenotype due to the action of natural selection.

7 1. What is a phylogenetic tree and what does it represent? 2. How are comparisons of the DNA of the gene shown used to build the phylogenetic tree (cladogram) shown? 3. How would a tree based on the analysis of a different gene or genes compare to this tree?

8 1. What is a phylogenetic tree and what does it represent? A phylogenetic tree represents a hypothesis that describes the evolutionary relationship between different species based on the idea of shared common ancestry. 2. How are comparisons of the DNA of the gene shown bused to build the phylogenetic tree (cladogram) shown? Each difference in DNA represents a mutation and the greater the number of mutations between two species, the longer the two have diverged due to being reproductively isolated. Two species that have few DNA differences have shared a common ancestor recently. 3. How would a tree based on the analysis of a different gene or genes compare to this tree? Results may vary. Analysis of different genes may result in different trees. The question is: are the results from the analysis of any given gene representative of the tree that would result from a comparison of a number of other genes?

9 1. Describe the pattern shown in the graph. 2. What is the mechanism behind this pattern? 3. How did the mosquito population evolve so rapidly to the new selective pressure (the use of a new pesticide called DDT)?

10 The increase in DDT resistance over 12 months is due to natural selection. Some mosquitos already had a genetic resistance. Resistant mosquitoes had a survival advantage and thus reproduced more than nonresistant mosquitoes and passed on the trait to the next generation.

11 Draw a phylogenetic tree that shows the evolutionary relationships between: tuna, pigeon, rhesus monkey, and humans Cytocrome c Protein Amino Acid Comparisons

12 Cytocrome c Protein Amino Acid Comparisons On the purple scratch-paper, draw a phylogenetic tree that shows the evolutionary relationships between: tuna, pigeon, rhesus monkey, and humans human rhesus pigeon Tuna

13 Use the data below to draw a phylogenetic tree that includes all of the species shown.

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15 Use the data shown below to draw a best-fit phylogenetic tree.

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17 Use the data below to draw a phylogenetic tree. Include labels for all of the character traits show.

18 Outgroup Dorsal fin Dorsal fin Dorsal fins independently evolved in tuna and dolphins

19 Which of the three possible hypotheses (trees) best fits the data? x x x 2 x x 3 3 x Ancestral species

20 x x x 2 x x 3 3 x Ancestral species

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24 Roundworm Fruit fly Dog Chimp Humans

25 1. Where, on the graph did the bottleneck occur? 2. Describe the relationship between population size and genetic variation up to just after the bottleneck: 3. Explain why genetic variation does not increase when the population rebounds:

26 1. Where, on the graph did the bottleneck occur? Where the blue line plummets 2. Describe the relationship between population size and genetic variation up to just after the bottleneck: When population size decreases (bottleneck) genetic diversity is lost at the same time 3. Explain why genetic variation does not increase when the population rebounds: Although population size can rebound quickly, genetic diversity can only be returned through mutation, which is rare and random

27 A population bottleneck is shown 1. Are allele frequencies likely to be the same after the bottleneck? Explain: 2. What is the likely effect on genetic diversity? Explain:

28 A population bottleneck is shown The allele frequencies after a population bottleneck are likely to change because genetic drift (a type of sampling error) will have a larger effect in a smaller population resulting in a random change in frequencies and loss of genetic diversity.

29 1. What is a population bottleneck? 2. What is the effect of this process on genetic diversity? 3. Why should we care? 4. How could this affect how a species responds to a new disease?

30 A population bottleneck occurs when a population is decreased in size. As a result, genetic diversity is lost. This is a concern because the species may thus have a difficulty adapting via natural selection to change. For example, the species may lack genetic diversity that includes genetic resistance to new diseases.

31 In the diagram above, connectivity increases in the habitat-patch designs from left to right. 1. How would the level of gene flow be affected? 2. How would genetic diversity be affected?

32 In the diagram above, connectivity increases in the habitat-patch designs from left to right. Gene flow would increase as connectivity does. Gene flow would make the effective population size larger (one large population vs. two smaller ones) and would therefore help to maintain genetic diversity.

33 What is the difference between a prezygotic and a postzygotic isolating mechanism?

34 What is the difference between a prezygotic and a postzygotic isolating mechanism? Prezygotic barriers prevent the union of sperm and egg to form a zygote Postzygotic barriers keep two species separate even if the egg was successfully fertilized

35 Briefly describe or give and example of Prezygotic Isolating Mechanisms: Habitat isolation Temporal isolation Behavioral Isolation Mechanical Isolation Gametic Isolation

36 Briefly describe or give and example of Prezygotic Isolating Mechanisms: Habitat isolation aquatic vs. terrestrial garter snakes; parasites on cats vs. dogs Temporal isolation E. vs. W. spotted skunks breed in different seasons; flowers open at different times Behavioral Isolation Bird songs & dances differ between different species Mechanical Isolation Left vs. right spiral shell of two snail species prevents genetalia from connecting Gametic Isolation The egg of one species of sea urchin does not recognize and therefore accept the protein coating on the sperm from another species

37 Briefly describe or give and example of Postzygotic Isolating Mechanisms: Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown

38 Briefly describe or give and example of Postzygotic Isolating Mechanisms: Reduced hybrid viability The sperm from one species of salamander successfully fertilizes the egg of another species, but the embryos fail to develop fully or if they do they are frail compared to others of either species Reduced hybrid fertility A male donkey and female horse can produce a viable offspring, a mule, but mules are not fertile (dead-end) Hybrid breakdown In rice plants, the hybrids are viable and fertile, but when they breed, their offspring are weak and frail (unlikely to survive to reproduce) making it a dead-end

39 These salamanders are still the same species. However, which isolating mechanism is at work in S. CA where the coastal and inland populations overlap? What could be the result over time?

40 These salamanders are still the same species. Hybrids of inland and coastal populations do not have the protective coloration strategy of either parent population and are thus less likely to survive. Over time, with continued reproductive isolation, 2 new species could result

41 1. Does the Hardy-Weinberg theorem describe an evolving or nonevolving population? 2. Explain what the terms in the Hardy-Weinberg equation represent. 3. Describe the conditions that are necessary for a population to be in equilibrium.

42 1. Does the Hardy-Weinberg theorem describe an evolving or nonevolving population? A nonevolving population 2. Explain what the terms in the Hardy-Weinberg equation represent. Q2 represents the frequency of the homozygous recessive genotype, 2pq the frequency of the heterozygous genotype and p2 the frequency of the homozygous genotype. Adding the frequency of all three genotypes together should represent 100% or a total frequency of Describe the conditions that are necessary for a population to be in equilibrium. Large population size, no net gene-flow (no emigration or immigration), no net mutation, random mating (no sexual selection), no natural selection

43 168 rock pocket mice were trapped at the study site. Of these 120 were light-colored and 48 were dark colored. Calculate the frequency of each genotype: dd DD Dd

44 168 rock pocket mice were trapped at the study site. Of these 120 were light-colored and 48 were dark colored. Calculate the frequency of each genotype: dd DD Dd q 2 = dd = 120/168 = 0.71 Take the square root to get q = 0.84 Therefore p = 0.16 P2 = DD = (0.16)2 = pq = Dd = 2(0.16)(0.84) = 0.27

45 The ability to taste PTC is due to a single dominate allele "T". You sampled 215 individuals in biology, and determined that 150 could detect the bitter taste of PTC and 65 could not. Calculate the frequencies of: homozygous dominant, heterozygous, and homozygous recessive

46 The ability to taste PTC is due to a single dominate allele "T". You sampled 215 individuals in biology, and determined that 150 could detect the bitter taste of PTC and 65 could not. Calculate the frequencies of: homozygous dominant, heterozygous, and homozygous recessive tt = 65/215 = 0.3 Square root of 0.3 = q = 0.55 therefore p = 0.45 P 2 = TT = (0.45) 2 = 0.2 2pq = Tt = 2(0.45)(0.55) = 0.5