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BEANZ Practice Examination Level 3 Biology Assessment Schedule 2011 Achievement Standard 90717 B 3.5 Describe patterns and processes of evolution Credits: 3 Assessment of AS 90717 paper: Students are given a grade for each question. The criteria for awarding question grades are given in the last row of each questions’ assessment schedule. The table below indicates how grades are allocated for the Standard. Total Questions i.e. maximum grades possible 4 3 grades total (A, M or E) Sufficiency Minimum 3A 4 3 grades total (A, M or E) plus 2 grades to be at M or E A + 2M 4 4 grades gained in total plus 3 grades to be at M or E, plus 2 grades to be at E A + M + 2E Question 1 Q1 a. The ‘Species Problem’ Evidence for Achieved Species defined: group of actively or potentially interbreeding individuals separated genetically from other such groups OR group of organisms that interbreed successfully (produce fertile offspring) in natural environments. Student must make a decision i.e. are the Black Stilt and the Pied Stilt the same species or not? Either answer is accepted as long as it is substantiated i.e. reasons must be attempted for Merit Or student can state that there is evidence to support either decision and then explain. b. Students cannot get ‘Achieved’ alone unless an attempt at an explanation is made. i.e. no guesses accepted. Evidence for Achieved with Merit Evidence for Achieved with Excellence 2 explanations of decision, these can be for the answer given or against the other choice Same species: interbreeding is possible and F1 hybrids are fertile (other hybrids exist) species have diverged recently and their divergence has not yet reached species level continued divergence (more time) is needed to establish separate species status etc Different species: Basis of separation into 2 species is morphological (based on colour) and habitat information which is still valid Hybrids are present but their fertility is not known. There is a suggestion of reduced fitness which would inhibit gene flow Species have until recent colonisation had geographical separation and interbreeding was geographically impossible etc Additional information required is based on the long term consequences of interbreeding i.e. F1 hybrids are fertile but if the offspring of hybrids show decreasing fertility with each generation then gene flow will be limited and the species must be considered separate Additional genetic or DNA information about the degree of genetic divergence would give some definitive information about how different the two species actually were or similar Any 2 examples described: lack of demarcation between sp and subsp. eg. ring species c. (successful) interbreeding between related species in captivity / gardens when one sp. is introduced into the habitat of another lack of demarcation between sequential sp. or ancient species defined on the basis of morphology Structural barriers to breeding between members of the same sp etc 2 examples explained: Neighbouring populations can interbreed (same species) but distant ones cannot Animals and plants removed from their natural environment often can interbreed with related species Species defined by time, how can ability of interbreeding ever be tested Interbreeding is prevented by factors that have been artificially selected for eg. between individuals of large and small dog breeds etc Total for Q 1 3a Assessment for Q 1 Student gains Achieved for this question if: 2 of 3 opportunities for ‘A’ are answered correctly. Minimum 2a 2m Student gains Achieved with Merit for this question if: 2 of 3 opportunities for ‘A’ are answered correctly and 1 of 2 opportunities for ‘M’ are answered correctly. 1a + 1m 1e Student gains Achieved with Excellence for this question if: 2 of 3 opportunities for ‘A’ are answered correctly 1 of 2 opportunities for ‘M’ are answered correctly and the opportunity for ‘E’ is answered correctly. 1a + 1e Question 2 Q2 a. b. c. Recent Speciation in Salsify Evidence for Achieved Speciation defined: any process that promotes divergence and leads to the formation of a new species Evidence for Evidence for Achieved with Merit Achieved with Excellence Speciation must be sympatric because: For allopolyploids to occur crosspollination (between the parental species) is required which means the parent must be growing in the same habitat i.e. sympatric (in the same place). NB it is not sufficient to simply explain what sympatric means. Description or implication Explanation explains that of what makes a plant a polyploidy exhibit ‘hybrid successful weed: vigour’. eg. i.e. because they contain a Allopolyploids have the ability wider range of genetic to compete, grow more material from 2 parental quickly and spread in habitats species they are able to cope where environmental factors with more extreme conditions that are less ideal or more and usually have higher likely to be limiting growth rates Description of allopolyploid Explanation of how Reproductive Isolating stated or implied: allopolyploids arise (are Mechanisms OR their produced): importance discussed: a polyploid that contains genetic material from 2 (or One of 2 mechanisms Allopolyploids are a ‘new’ more) parental species. explained species because they are 1. Fusion (fertilisation) that ‘reproductively isolated’ from involves 2 nonother species (including their disjoined gametes parental species by hybrid infertility. This means that i.e. 2 gametes with 2n chromosomes (that have any fertilisation between a 4n not separated at meiosis) species (gametes 2n) and a form a 4n zygote 2n species (gametes n) will 2. A polyploid that results result in a 3n hybrid, which from the doubling of will be infertile. chromosome number RIMs are important because in an otherwise infertile they prevent gene flow hybrid at the first mitosis between the 2 populations. after fertilisation This in turn allows divergence (effectively a 2n zygote to occur / action of selective becomes a 4n zygote) pressures or natural selection. (2 ideas; no gene flow and divergence) Total for Q 2 3a 3m Assessment for Q 2 Student gains Achieved for this question if: 2 of 3 opportunities for ‘A’ are answered correctly. Student gains Achieved with Merit for this question if: 2 of 3 opportunities for ‘A’ are answered correctly 2 of 3 opportunities M’ are answered correctly. Minimum 2a 2m 1e Student gains Achieved with Excellence for this question if: 3 of 3 opportunities for ‘A’ are answered correctly 2 of 3 opportunities for ‘M’ are answered correctly and the opportunity for ‘E’ is answered correctly. 1a + 1m + 1e Question 3 Q3 a. Divergence or Convergence? - The Lord Howe Tree Lobster Evidence for Evidence for Achieved Achieved with Merit Bottleneck Explanation of how or why genetic effect defined diversity is reduced (short-term effect): or described. Small number of individuals will only carry a Loss of smaller number of genes present in the genetic original larger population (some alleles may diversity due be lost altogether) to small This will lead to a loss of genetic diversity population (assuming the population regains its former size. size) OK if student uses the term Genetic drift. b. Divergence and Convergence both described: Divergence: Evolution in which 2 or more species evolve from a common ancestor Convergence: Evolution in which 2 or more unrelated species (no common ancestor) evolve similar adaptations in response to similar niche requirements Total for Q 3 Assessment for Q 3 Minimum Evidence for Achieved with Excellence Discussion of long-term consequences for the recovering population If population size recovers, lack of diversity may limit adaptive potential (until new variations appear due to mutations, independent. assortment, crossing over &/or recombination). Conversely some alleles that were rare may i.e. become more common because (by population will initially not have chance) they were over-represented in the the genetic diversity that will allow small population it to respond to environmental changes. Outline the conditions that would have been 2 or more types of necessary for both mechanisms to occur evidence is evaluated: Divergence: Anatomical features and ecology i.e. Any 2 or more conditions Common ancestor that disperses and colonises morphology, adaptations and niche. These are new islands superficially similar (due mechanism that prevents gene flow between to convergence) although populations, e.g. geographic separation they appear to be due to different adaptive forces / natural selection divergence. forces acting on different populations sufficient time is needed for the accumulation of DNA analysis Genetic evidence sufficient genetic differences indicates that these resulting genetic changes developing in insects had different isolated populations leading to divergence (2 ancestors / origins. different but related species) Morphological similarities etc can be generated and Convergence: selected for in genetically Any 2 or more conditions different ways unrelated ancestors present on different Other evidence: islands eg unoccupied niches are available Genetic comparisons with similar adaptations evolve because they possible ancestors occupy similar niches Fossils evidence populations are subject to similar selective (possible but not likely) pressures (similar environments) etc etc acceptable if evaluated 2a Student gains Achieved for this question if: both opportunities for ‘A’ are answered correctly. 2a 2m Student gains Achieved with Merit for this question if: both opportunities for ‘A’ are answered correctly and 1 of 2 opportunities for ‘M’ is answered correctly. 1a + 1m 2e Student gains Achieved with Excellence for this question if: both opportunities for ‘A’ are answered correctly both opportunities for ‘M’ are answered correctly and 1 of 2 opportunities for ‘E’ is answered correctly. 1m + 1e Question 4 Q4 a. The Evolution of Fresh-water Eels Evidence for Achieved Title has 2 parts and must be descriptive: 1. Divergence / Phylogeny etc of 2. freshwater Eels / genus Anguilla. Or similar mtDNA is inherited from one (female) parent only. i.e. mtDNA is inherited via the direct female line. b. Dispersal and colonisation both described Movement to new geographic area and establishment of breeding population there. c. i. Evidence for Achieved with Merit Evidence for Achieved with Excellence mtDNA can only change by mutation (mutations are more common than in nuclear DNA due to the lack of repair mechanisms) or mtDNA is not subject to recombination and is thus inherited unchanged (except for accumulated mutations). Circumstances explained (at least one explanation needed): juveniles are carried by ocean currents to new river systems (explanation involves colder currents, slower growth, longer juvenile period and longer time for migration to fresh water) movement to Africa and Oceania is possible because oceans are connected but movement to Atlantic occurred before Africa moved to its present position – Indian, Mediterranean, Atlantic were connected. New breeding population was isolated from the parental population i.e. geographically, temporally due to temps and growth rates etc or some other feasible mechanism. etc Divergence and speciation defined or implied Or Natural selection defined or implied c. Mechanism of speciation explained: Geographic separation of populations prevents gene flow. As a result of different natural selection pressures the gene pools diverge until different species result Or Mechanisms of Natural Selection explained In geographically separate areas gene pools respond to the different selection pressures that operate in those areas (examples include temperature and food sources etc. temp causes slower juvenile growth etc) ii. Elaboration of present day distribution. One of the following elaborated on: Majority of species occur in the Indo-Pacific because it is the centre-of-origin of the genus and because geographic isolation (and prevention of gene flow between populations) is more easily achieved in tropical areas where migration distances are shorter due to faster growth rates. In temperate areas greater distances between populations are needed to achieve isolation because juveniles spend more time at sea and can cover greater distances – carried by currents. Hence Africa 1 sp. only and N. Atlantic 2 sp. only Many areas do not have any eel species despite oceanic connections eg S Atlantic, N and E Pacific. Reasons could include: o lack of ocean currents that encourage dispersal to those areas o distances are too great so that even if currents were suitable the time involved would be too great and juveniles need to migrate into freshwater o lack of suitable spawning areas with suitable ocean currents that carry migrating juveniles to suitable freshwater habitats and adults back to the spawning areas. i.e. round-trip migration is not possible o etc. Total for Q 4 4a 3m Assessment for Q 4 Student gains Achieved for this question if: 3 of 4 opportunities for ‘A’ are answered correctly. Student gains Achieved with Merit for this question if: 3 of 4 opportunities for ‘A’ are answered correctly and 2 of 3 opportunities for ‘M’ are answered correctly. Minimum 3a 1a + 2m 1e Student gains Achieved with Excellence for this question if: 3 of 4 opportunities for ‘A’ are answered correctly 2 of 3 opportunities for ‘M’ are answered correctly and the opportunity for ‘E’ is answered correctly. 1a + 1m + 1e