PERIOD 5, SHIRE: Chapter 25 FRQ - Neha Athavale Kevin Bei Elena Chan Purba Khan Christine Law Shire P.5 Chapter 25 Heterochrony and Paedomorphosis Study

PERIOD 5, SHIRE: Chapter 25 FRQ - Neha Athavale Kevin Bei...

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Neha Athavale Kevin Bei Elena Chan Purba Khan Christine Law Shire P.5 Chapter 25 Heterochrony and Paedomorphosis Study Packet Response Form: LINK TO SCIENTIFIC STUDY: Heterochrony repolarized: a phylogenetic analysis of developmental timing in plethodontid salamanders Supplemental Studies: Heterochrony FRQ Answers must be in essay form. Outline form is not acceptable. Labeled diagrams may be used to supplement discussion, but in no case will a diagram alone suffice. It is important that you read each question completely before you begin to write. Heterochrony is an evolutionary change in the rate or timing of developmental events. It can also alter the timing of reproductive development relative to the development of non- reproductive organs. In one such example of heterochrony, paedomorphosis, juvenile structures may still be present in the sexually mature. Plethodontid salamanders, specifically the Serpelini tribe, demonstrate heterochrony because they show multiple variations in the timing of metamorphosis and with the independent instances of paedomorphosis--larval stage.
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a) Define what paedomorphosis is in relation to heterochrony. b) Analyze the graphs and explain the different life history patterns through the phases of egg, larva/paedomorph, then metamorph. c) Identify which life history pattern salamanders follow, and justify how it can give them an evolutionary advantage. ( RUBRIC ON NEXT PAGE ) RUBRIC
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75% Rule - If the student has 75% of the requirements, then they can get the points. Part A: Definition of Paedomorphosis -- MAXIMUM: 1 POINT Present Absent Sexual maturity of an animal while in its larval stage Retardation of bodily development with respect to reproductive activity Paedomorphosis is a type of heterochrony. Juvenile structures are present in a full grown adult Part B: Graphs of Life History Patterns -- MAXIMUM: 6 POINTS (must have at least 2 out of 3 in each type of graph) Present Absent Direct Development (dd) Egg: They have a short stage before continuing on the next stage Larva/Paedomorph: This stage is nonexistent. Metamorph: The longest and the last phase. Biphasic (bi) Egg: This phase is the shortest out of the three. Larva/Paedomorph: The duration of this phase is identical to the metamorph phase Metamorph: They entered the metamorph stage once they reached complete maturation Paedomorphic (pd) Egg: This phase is the shortest. Seems to be of the whole life phase. Larva/Paedomorph: This phase takes up the majority and it is at this stage when it reaches complete maturation Metamorph: This phase is nonexistent. Part C: Connection of Salamander Example -- MAXIMUM: 3 POINTS *Must identify to get any points!* Present Absent Identification of Life History Pattern Paedomorphic Connection of Salamander to Evolutionary Advantage Allows adults to exploit different habitats to larvae Utilize a wider range of ecological niches Escape from potentially hostile environments Total: ___/10 SAMPLE ANSWERS & JUSTIFICATION
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Sample Answer #1 a. Paedomorphosis is a type of heterochrony (1)
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