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1974 1981 1982 1984 1986 1989 1990
EVOLUTION QUESTION - 1974 L. PETERSON/ECHS Hereditary variations are essential to the evolution of populations. A. Describe the different types of hereditary variability. B. Explain how this variability can lead to the origin and maintenance of species. STANDARDS: Total points possible for Part A and Part B = 18. Candidates receiving 15, 16, 17,or 18 points are given a score of 15 for this essay. PART A. (19 possible responses, with a maximum of 9 points given for this section) For the seven mutation types that follow, 1/2 point is given for the naming, 1/2 point is given for explaining, for a total of 7 possible responses; Maximum of 6 points given. MUTATION TYPES: point, deletion, duplication, inversion, translocation, polysomy, polyploidy MUTATION ORIGIN: spontaneous or induced (listing inducing agent) - 1 point; mechanism of induction or of mutation or relating process to evolution - 1 point; mutations are rare, random, or usually deleterious - 1 point each; EFFECTS OF MUTATIONS: Indicate with some explicitness the type(s) of phenotypic effects - 1 point; spell out how the gene change leads to phenotypic change - 1 point; Recombination: independent assortment, crossing-over - 1 point; role of sex in facilitating recombination - 1 point; any consideration of asexual reproduction - 1 point; "hidden" variation: epistasis - 1 point; PART B. (12 possible responses, with a maximum of 9 points given) Only inherited (germ-line) changes are important - 1 point; POPULATION CHANGE DURING EVOLUTION NATURAL SELECTION: The fittest, in relation to environment, survive - 1 point; mechanism involves differential survival &/or reproduction - 1 point; GENETIC DRIFT: random change in gene frequencies in small populations 1 point; may account for large number of alleles in large populations - 1 point; CONTINUOUSLY CHANGING ENVIRONMENT: leads to continuing evolution - 1 point; SPECIATION GEOGRAPHIC: Isolation leads to divergence - 1 point; mechanism for the build-up of difference - 1 point; Sympatric: an isolating device; for example: seasonal, habitat, behavioral, hybrid inviability, infertility - 1 point/with a maximum of 2 points; AN EXAMPLE OF A CHANGED GENE OR PHENOTYPE OR FREQUENCY OR ENVIRONMENTAL CHANGE: 1 point for each response, with a maximum of 2 points;
EVOLUTION QUESTION - 1981 L. PETERSON/ECHS Define, discuss, and given an example of how each of the following isolating mechanisms contributes to speciation in organisms. A. Geographical barriers B. Ecological (including seasonal) isolation C. Behavioral isolation D. Polyploidy STANDARDS: The concept of speciation was worthy of points, but a student could achieve a score of 15 without including a discussion of speciation. Any student who omitted any reference to any of the other four parts could achieve only a maximum of 12 points. Within these limits, a single point was given for every valid idea presented. SPECIATION: 1. Reproductive isolation by mutations and changes in gene pools. 2. Definition of a new species. 3. Adaptations (environmental and behavioral) may continue isolation after barriers no longer exist. A. GEOGRAPHICAL BARRIERS: 1. Types of barriers that can physically separate populations. 2. Most speciation initiated by barriers. 3. Genetic drift and/or founder effect contribute to isolation. 4. Barriers may result in environments that produce different selective pressures. 5. Example (actual or theoretical). B. ECOLOGICAL ISOLATION: 1. Allopatric populations can no longer occupy the same range due to adaptations to climate, food, etc. 2. Sympatric populations can demonstrate habitat or niche isolation. 3. Seasonal variations in fertility cycles or migratory patterns. 4. Example (actual or theoretical). C. BEHAVIORAL ISOLATION: 1. Variation in courtship/auditory signals. 2. Pheromones. 3. Territoriality may lead to dispersal and establishment of peripheral populations. 4. Example (actual or theoretical). D. POLYPLOIDY: 1. Definition. 2. Cellular processes resulting in polyploidy. 3. More commonly a speciation factor in plants. 4. Autopolyploidy/allopolyploidy. 5. Hybrid species formation often increases the survival rate. 6. Polyploidy is "instant" speciation. 7. Example (actual or theoretical).
1982 EVOLUTION QUESTION - 1982 L. PETERSON/ECHS Describe the special relationship between the two terms in each of the following pairs: A. Convergent evolution of organisms and Australia B. Blood groups and genetic drift C. Birds of prey and DDT STANDARDS: (15 points maximum/1 point for each of the following) CONVERGENT EVOLUTION / AUSTRALIA different phylogenetically - similar environment selection pressures - niche adaptation ecological equivalence analogous structures role of isolation - island populations continental drift marsupial vs. eutherian mammals example BLOOD GROUPS / GENETIC DRIFT co-dominant alleles - polymorphic = multiple genetic traits Hardy-Weinberg and small populations tend toward homozygosity change in gene frequency bottle-neck effect - founder effect selection pressures cause Genetic Drift - selective advantages examples of populations - Indians, Gypsies..... BIRDS OF PREY / DDT food chains - trophic levels - biomass pyramid of biomass diagram DDT persistent pesticide - chlorinated hydrocarbon biological manifestation resistance increases concentration hormone regulating Ca+2 destroyed thin or fragile eggs - decrease reproductive rate
EVOLUTION QUESTION - 1984 L. PETERSON/ECHS Describe the modern theory of evolution and discuss how it is supported by evidence from two of the following three areas: a. Population genetics b. Molecular biology c. Comparative anatomy and embryology STANDARDS: No paper may receive more than 12 points unless 2 sections from ABC and description of the Modern Theory are covered. DESCRIPTION OF THE MODERN EVOLUTION THEORY 1 - Synthesis Theory 1 - Darwin 1 - work of Darwin, contribution * - role of Natural Selection: 1 survival 1 variability 1 overpopulation 1 gene perpetuation * all of the above must have explanation 1 - effects of mutation POPULATION GENETICS (6 points - max.) 1 - definition 1 - fusion of Darwin and Mendel 1 - Hardy-Weinberg 1 - mathematical Model 1 - assumptions and explanation 1 - (OR negative/i.e. nonrandom mating, mutation, etc.) 1 - genetic drift 1 - types and example 1 - equilibrium or stability (loss = evolution) 1 - mechanism of speciation (isolation, barriers) 1 - coevolution 1 - adaptive radiation (gene pool) MOLECULAR BIOLOGY (6 points - max.) 1 - genetic variation from mutation 1 - types of mutation (addition, substitution, etc.) 1 - heterozygote vigor 1 - example 1 - comparative Biochemistry (DNA, cytochrome C, protein, amino acid sequence) 1 - carbohydrate metabolism 1 - common molecule/common function 1 - phylogenetic trees from amino acid sequence 1 - biochemistry techniques: hybridization of DNA, sequencing, etc. COMPARATIVE ANATOMY/EMBRYOLOGY (6 points - max.) 1 - definition/description 1 - convergent evolution 1 - divergent evolution 1 - example 1 - homologous/analogous 1 - vestigial organs 1 - example of above 1 - adaptive radiation (structural aspects) 1 - comparison of larval stages 1 - comparison of embryos 1 - common ancestor for close resemblance 1 - example (max 1): heart chambers gill slits/pharyngeal pouches tails cervical vertebrae plus 1 for good explanation of revision of Haekel's theory
EVOLUTION QUESTION - 1986 L. PETERSON/ECHS Describe the process of speciation. Include in your discussion the factors that may contribute to the maintenance of genetic isolation. STANDARDS: DESCRIBE PROCESS (max. 9 points) 1 - Definition of speciation 1 - Differences in populations 1 - Barriers occur (various kinds) 1 - Barriers prevent inbreeding 1 - Mutations responsible for differences 1 - Differences (variations) result in populations 1 - Genetic drift occurs in small populations 1 - Founder effect (populations markedly different from parents) 1 - Differential selection pressures (environmental) 1 - Adaptive radiation, divergence 1 - Hardy-Weinberg Assumptions (how population size, random mating affects speciatio ) 1 - Polyploidy (related to speciation) 1 - Allopolyploidy (two different species) 1 - Sympatry 1 - Allopatry MAINTENANCE OF GENETIC ISOLATION (max. 9 points) 1 - Mechanical isolation (structural, prevents mating) 1 - Seasonal isolation (different mating seasons) 1 - Habitat isolation (don't encounter each other) 1 - Behavioral isolation (courtship, mating behaviors differ, songs, etc.) 1 - Gamete isolation (gametes can't live in reproductive tract of other species) 1 - Hybrid sterility (vigorous, infertile hybrids) 1 - Hybrid elimination (hybrids fertile, not competitive) 1 - Hybrid weakness (weak, malformed hybrids, die young) 1 - Developmental incompatibility (embryo-parent) [Maximum for examples in either section - 2 additional points]
EVOLUTION QUESTION - 1989 L. PETERSON/ECHS Do the following with reference to the Hardy-Weinberg model. A. Indicate the conditions under which allelic frequencies (p and q) remain constant from one generation to the next. B. Calculate, showing all work, the frequencies of the alleles and the frequencies of the genotypes in a population of 100,000 rabbits, of which 25,000 are white and 75,000 are agouti. (In rabbits the white color is due to a recessive allele, w, and agouti is due to a dominant allele, W.) C. If the homozygous dominant condition were to become lethal, what would happen to the allelic and genotypic frequencies in the rabbit population after two generations? STANDARDS: A. CONDITIONS FOR HARDY-WEINBERG: H-W applies if: large population size (1 pt) no genetic drift or founder effect random mating (1 pt) no mating preference or inbreeding no mutation (1 pt) no selection (1 pt) all genotypes have equal chance to reproduce no migration (1 pt) no differential migration; no gene flow among populations; _________________ 5 pts Max 3 B. PROBLEM formula (1 pt) p2 + 2pq + q 2 = 1 relationship to genotypes WW Ww ww or W = p (1 pt) w = q definition of all terms of equation calculation to frequency 25,000/100,000 = frequency ww = q2 (1 pt) = 0.25 or 1/4 or 25% allele frequencies (2 pts) q = .25 = .5 = frequency of w (1 pt if no explanation) formula (1 pt) since p + q = 1 p = 1 - q = .5 frequency of W genotype frequencies p2 = (.5)2 = .25 - WW (3 pts) 2pq = 2(.5) (.5) = .5 = Ww q2 = (.5)2 = .25 = ww or 1 pt for frequencies with no explanation or W w ____.5__.5____ W .5 .25 .25 ________________ w .5 .25 .25 (in context) _________________ 9 pts Max 6 C. APPLICATIONS (WW genotypes die) genotype frequency changes p2 decreases (does not disappear) (1 pt) or Ww decreases &/or ww increases or 2 pq decreases &/or q2 increases or heterozygotes decrease &/or homozygotes increase allele frequency changes p decreases (but is not eliminated because of (1 pt) heterozygotes) q increases Bonus: Some discussion e.g. selection (1 pt) death of homozygotes due to selection (decreased fitness) fitness = 0 s = 1 A rare student may know that in 2 generations p is halved i.e. p = .25, q = .75 If n = # of generations = 2 pn - po /(1 + npo) = .5/(1+2(.5)-.25 p2 = .06; 2 pq = .38; q2 = .56 ____________________ 4 pts Max 2
EVOLUTION QUESTION 1990: L. PETERSON/ECHS A. Describe the differences between the terms in each of the following pairs. (1) Coelomate versus acoelomate body plan (2) Protostome versus deuterostome development (3) Radial versus bilateral symmetry B. Explain how each of these pairs of features was important in constructing the phylogenetic tree shown below. Use specific examples from the tree in your discussion. Chordata Arthropoda Annelida Echinodermata Mollusca Nematoda Rotifera Platyhelminthes Cnidaria Porifera STANDARDS: A. (1) COELOMATE VS. ACOELOMATE 1 - Coelomate: internal body cavity lined with mesoderm (not sufficient to say: "true body cavity") 1 - Acoelomate: lacking internal cavities altogether or having: a pseudocoelom (Nematoda and Rotifera) a spongocoel (Porifera) mesoglea (Cnidaria) a solid layer of mesoderm (Platyhelminthes) [Max. = 2 / must define both for full credit] (2) PROTOSTOME VS. DEUTEROSTOME DEVELOPMENT 1 - Protostome: mouth develops near/at the blastopore or anus forms secondarily (later), OR featuring: spiral cleavage (micromeres between macromeres); determinate/mosaic development (blastomere fate is established at very early stages of development); mesoderm from cells that migrate into the blastocoel near blastopore schizocoelous coelomation (internal split in solid wedge of mesoderm that is independent of gut); trochophore larva; 1 - Deuterostome: anus develops near/at the blastopore or the mouth forms secondarily (later), OR featuring: radial cleavage (micromeres directly above macromeres); indeterminate/regulative development (blastopore fate is variable and not established until late in development); mesoderm arises from outpocketings of the gut; enterocoelous coelomation (outpocketings of gut); dipleurula larva [Max. = 2 / must define both for full credit] (3) RADIAL VS. BILATERAL SYMMETRY 1 - Radial: several planes passing through the long or central axis can divide the organism into similar parts. 1 - Bilateral: (only) one plane passing through the long axis divides the organism into similar right and left sides -- exhibits cephalization. 1 - Echinoderms: bilaterally symmetrical larvae, but appear to have radially symmetrical adult forms. [Max. = 2] B. PHYLOGENETIC TREE 1 - for examples of contrasting pairs (phyla or organisms) using terms from above; answer here or in part A. 1 - for using above terms in explanation of why phyla are in separate groups (or separate branches) of the tree. 1/1 - Body symmetry (cephalization) permits separation of Porifera and Cnidaria (radially symmetrical) from other phyla (bilaterally symmetrical). 1/1 - Coelomation permits separation of Platyhelminthes, Nematoda, and Rotifera from other phyla above Cnidaria: flatworms are acoelomate, whereas those other than nematodes and rotifers are coelomate. 1/1 - Origin of the mouth and anus permit separation of Echinodermata and Chordata (deuterostomes) from Arthropoda, Annelida, and Mollusca (protostomes). [Some include Platyhelminthes, Nematodes, and Rotifers as protostomes.] 1 - Nematodes and rotifers are grouped separately because both are pseudocoelomate. 1 - Phylogenetic trees based taxonomic relationships on homologous structures, patterns of embryonic development, and common ancestry. [Max. = 6]