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Selection and Speciation

Explore how environmental pressures drive evolution and speciation. Learn when population changes are significant enough for scientists to identify a new species.

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    Selection and Speciation E low can changes in a population result in the iormation of a new species? Why?__________________________________________ I lave you ever wondered how the great diversity of life on E arth has come about or how a single new spe- cies forms? Environmental pressures may cause populations to change over time or evolve. This is because an organism's ability to live to adulthood in its current environment will determine its reproductive suc- cess and ability to pass on its genes. But changes within a population can occur without creating a new species. Ar what point do scientists start thinking of a new name for a species? Model 1 - Three Types of Selection Directional Selection Disruptive Selection 0 >0 L(M I B 1-10 175 0 r> V.y Ml 61V 75 U.V ]« ■ 11 I 2> 1>7.> IMJ Body Size Jg> Body Sizt (g) Stabilizing Selection Number of Individuals Origitul pypuLtion Ihipulanon after selection 0 23 30 75 1W 12> lyO Body Sue fp) I. What variables do the graphs in Model I compare? Body size 2. What are the three types oE selection illustrated in the graphs in Model 1? Directional, Disruptive, Stabilizing Selection and Speciation 1

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    3- According to the graphs tn Model I, there is variation in the body mass in rhe original popula- tion. Using your knowledge ol genetics, describe how this variation is possible. The 4xd rarartxs rj; zaji'g a d f ri'» boz,' "azz 4. Reler to graph A of Model I . a . 1 low is the population that has experienced selection diflerent from the original population? T's 'cj f :r srs arjar b. Fitness is defined as the relative ability of an individual (or population) to survive, reproduce, and pass on genes. Which individuals in the original population appear to display better fitness? The area +ta»hue arjar : c 4i f -** i c. As a group, propose some characteristics ol the environment that could lead to the population changes illustrated in graph A. P c ira-a 5- Reler to graph B of Model I. a . 1 low is the population that has experienced selection diflerent from the original population? n J ' x a B n i r -han 4e crjj'i fcj-a- : n b. Which individuals in the original population appear to display better fitness? T'zu •x'+, xr;«r z- nrular t<x> 4 mosau c. A s a group, propose some characteristics ol the environment that could lead to the population changes illustrated in graph B. -':*42-zr r a n pviifcn. Tta arrair oral tan bias ard jqfr art ir- axaj <q»Ltz<ij POG1L™ Activities for AP* Biology 2

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    6. Relrr to graph C of Model 1. ji. 1 low Is the population that has experienced selection dilierent from the original population? Haar of rtre era -n +fa rriiHfa b. Which individuals in the original population appear to display better fitness? In th; - szji zody c. As a group, propose some characteristics of the environment that could lead to rhe population changes illustrated in graph C. 7. As a group, define the tollowing terms in grammatically correct sentences. Each definition should contain the following words: population, selection, fitness, and environment. a: Directional selection In :Tscr:-i z; irr ea r <.rc-<Ticra ccndhri cr an enwonnenfaajcrs As saaefcn cr rrftj dial urn a harfcfar octane trot eiy acaj al attci uitfi traita cr lusmnaiB. b. Disruptive selection DbnpHun :r faxis rdh ziiar: a pcfu ar f c+rarothate fhar haue rrasi +c r ar i". ixfiirdrj’E-ak a\ca;<£ Irate cz£ : i r. Stabilizing selection Statitdig sciicfian fakirs -nfiiidiasc- "tarrednti es?s '-if Fv jsgraata" fifaBSS fa u n w a ir ar anwrawnt , JiJa ntwhas T u.ie ■ ‘-STK frata triir asa are saactasaj-rs'. Selection and Speciation 3

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