L121 sp24 St5 As3 (3)

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University of Nebraska, Lincoln *

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121

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Biology

Date

May 15, 2024

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docx

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3

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LIFE 121 Standard 5 Phylogeny: Assignment 3 P ROBLEM SET S TANDARD 5: P HYLOGENY ; U SE MODELS TO ILLUSTRATE AND EXPLAIN SPECIATION AND RELATEDNESS . Learning Objectives: Interpret relatedness among species from a phylogeny. Make a phylogenetic hypothesis from observations. Use phylogenetic trees to demonstrate that homologous characters reflect shared ancestry but that convergent traits do not. Build a phylogenetic tree using a pairwise similarity (or difference) matrix. Draw phylogenetic trees that represent alternative hypotheses for patterns of speciation. Reading: Chapter 20 The Snapping Shrimp Two hypotheses can explain the pattern of species distribution in snapping shrimp seen in the figure below. Hypothesis 1: Speciation was caused by the formation of the Isthmus of Panama. Hypothesis 2: Speciation was caused by prezygotic behavioral barriers to gene flow. 1. Which hypothesis 1 or 2, proposes sympatric speciation? 2. Circle T or F for each of the statements related to the snapping shrimp species tree below. T F The two species within the Atlantic Ocean are more closely related to each other than they are to the species in the Pacific Ocean. T F The species tree suggests that geographic isolation contributed to speciation in allopatry. T F A. panamensis is more closely related to A. formosus than A. nuttingi T F The species tree indicates that A. panamensis, A. nuttingi and A. millsae all radiated from an A. formosus -like ancestor Edited: 2.24.2024 GVB Page 1 of 3
LIFE 121 Standard 5 Phylogeny: Assignment 3 4. Draw an alternative species tree for these 4 species that would support the hypothesis that the species in the Pacific Ocean are the result of the colonization of the Pacific Ocean by A. nuttingi after the Isthmus of Panama formed followed by adaptive species radiation into new habitats. 3. Use the morphological traits to build a phylogenetic tree of plants. Label the traits on your tree. PLANTS ginkg o biloba creeping liverwort gree n alga e lady tulip tufted lacefer n bisho p pine TRAITS stomat a X X X X needle s X cuticle X X X X X seeds X X X flower s X cones X X Edited: 2.24.2024 GVB Page 2 of 3
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