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Lecture 7

BIOL 230 Lecture 7: BIOL 230- Week 4 Learning Outcomes

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BIOL 230
Christopher Kopp

BIOL 230- Week 4 Learning Outcomes: Lecture 7: Population Distribution and Abundance Life cycle evolution  Life Stages: o Different life history stages can evolve independently in response to size and habitat specific selection pressures  Complex life cycles can help minimize drawbacks of small, vulnerable early stages o Functional specialization of stages is a common feature of complex life cycles  Many insects have larval stage that remains in small area, such as on a single plant (many butterflies)  The larvae are specialized for feeding and growth, and have few morphological feature other than jaws  The adult insect is specialized for dispersal and reproduction  Some adults, such as mayflies, are incapable of feeding and live only a few hours  Take advantages of different conditions and different resources Population distributions and abundances 1.Understand that populations vary in size across time and space  Population size and density: o Population size: the number of individuals in a population o Population density: the number of individual per unit area  Can be difficult to estimate if we don’t know how far individuals or their gametes can travel  What is an individual: o Many species can reproduce asexually  Individuals can produce genetically identical copies of themselves (clones)  Genet- colony of interconnected ramets  Ramets- individual clones, still compete with one another for light  Ex. Trees clones clump is a genet, the one tree from the clump is a ramet  Distribution and abundance change over time and space: o Ex. Humans distributed from Africa to other places in the world and abundance increased as well  Distribution and Abundance of a species is not homogeneous o There are spatial and temporal fluctuations in abundance of nearly all species 2.Know that multiple factors determine the distribution and abundance to organisms  What limits the geographic range? o Range boundaries are set by both abiotic and biotic factors o Limiting factors vary from species to species and across the range of a species  At the polar and upper boundary of a range, temperature may be primary limiting factor  At the equator and lower boundary of a range, competition may bee the primary limiting factor  Factors limiting the distribution of Bristlecone pines? o Upper limit: Temperature  Timberline has fluctuated with past climate o Intermediate boundaries: soil type o Lower limit: Competition  Sharp boundary between range of bristlecones and range of Utah juniper and pinon pine  But moisture might also contribute  Distribution Limits: o No single factor limits a species’ range o Different factors may act as limits at different parts of the range o Several factors usually are interacting to prevent expansion of a population  What is dispersal: o Dispersal: the movement of organisms away from their point of origin  All organisms have some capacity to move from their birthplace to a new site  Dispersal is not migration: regular movement to and from a specific place  Dispersal and range expansion: o To expand its range, a species must be able to:  1.Travel to a new area.  2.Withstand potentially unfavorable conditions along the way.  3.Establish A viable population when it arrives.  Dispersal is adaptive: o Natural selection favors individuals that travel only modest distance from natal site o A nearby site is likely to be more favorable than an individual’s exact birth place  Don’t want to compete with parents of sibling o Don’t want to disperse too far from natal site due to
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