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Ch. 42 Notes

by: Amanda Notetaker

Ch. 42 Notes 012

Amanda Notetaker
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These notes cover population ecology, discussed in chapter 42 of the textbook.
Exploring Biology
Dr. Hill
Class Notes
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This 4 page Class Notes was uploaded by Amanda Notetaker on Sunday April 17, 2016. The Class Notes belongs to 012 at University of Vermont taught by Dr. Hill in Fall 2016. Since its upload, it has received 20 views. For similar materials see Exploring Biology in Biomedical Engineering at University of Vermont.

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Date Created: 04/17/16
CH. 42 Populations 42.1: Populations Are Patchy in Space and Dynamic over Time Populations: groups of individuals of the same species -   Populations have properties that individuals lack -   Must understand populations to understand larger ecological systems Population Density: number of individuals per unit area/volume -   Measured if interested in causes/consequences of local abundance -   Dynamic, changes over time Population Size: total number of individuals in a population -   Population size = (Population Density) x (Area occupied by the population) Humans are interested in understanding species abundance: o   To increase populations of species that provide resources/food o   To decrease abundance of crop pests, pathogens, etc. -   Varies on spatial scales: Geographic Range: region in which a species is found Habitat Patches: suitable habitat separated by areas of unsuitable habitat 42.2: Births Increase and Deaths Decrease Population Size 1 Law of Population Growth: Under constant conditions anything should grow exponentially BD Model: “Birth-Death” model of population size Nt+1= N t B – D N: Population Size B: # births D: # deaths Population Growth Rate: changes in size over time period -   Change in population size can only be measured for very small populations ∆???? ∆???? = ???? − ????   Growth rates are estimated using… -   Per capita birth rate (b): # offspring produced by the avg. individual -   Per capita death rate (d): average individual’s chance of dying -   Per capita growth rate (r) = (b - d) Nt+1= N t (b-d) N àt N t+1= N t rN t If b > d, then r > 0 (population grows) If b < d, then r < 0 (population shrinks) If b = d, then r = 0 (no change) ∆???? -   Exponential/Instantaneous Growth Rate: ∆???? = ???????? 42.3: Life Histories Determine Population Growth Rates Demography: study of processes that influence birth, death and population growth Life History: sequence of key events that occur during individual’s life (growth, development, reproduction, death) -   “Strategies that solve an ecological problem” -   Covers 3 main classes of traits in organisms that contribute to overall fitness o   Age/size at maturity o   Number/size of offspring o   Lifespan/Reproductive Investment Survivorship: fraction of individuals that survive from birth to different life stages/ages Mortality: (= 1 - survivorship) those that don’t survive from birth to life stage Fecundity: Average # of offspring each individual produces at those life stages -   Increased fecundity/survivorship à Increased “r” Resources: materials/energy and time available to acquire them (in individuals & environment) -   Differs from physical conditions that organisms are able to tolerate o   Resources can be used up whereas conditions are experienced -   Must devote some resources to activities involved in obtaining more resources Principle of Allocation: a unit of a resource can only be used for one function at a time (Ex: maintenance, growth, defense, reproduction) -   Maintenance (maintaining hometostasis) is almost always first priority o   In stressful conditions, majority of resources go toward maintenance o   In normal conditions, more toward maintenance but others close in priority -   Life-History Trade-offs: negative relationships among growth, reproduction and survival o   Ex: Those that invest more in growth early in life cannot also invest in defense à Larger adult size, but lower survivorship 42.4: Populations Grow Multiplicatively, but the Multiplier Can Change Multiplicative Growth: a multiple of the population size (N) is added each period of time -   Populations don’t grow multiplicatively for very long, eventually reach steady size -   Doubling Time: Population doubles when the number individuals added = the initial population at a specific time (Increases as “r” decreases; inverse relationship) ????????2 ????▯▯▯▯▯▯ =   ???? Additive Growth: a certain number of individuals is added each period of time Density Dependent: Population density increases, r decreases (growth rate dN/dt approaches 0) -   Equilibrium: when r = 0, population stops changing in size -   Carrying Capacity (K): reaches equilibrium size; # of individuals an environment can support indefinitely (in closed system) o   Spatial environmental factors can result in variation of “K” o   Temporal variation in environmental conditions can cause population to fluctuate above/below “K” Exponential Growth: dN/dt = rN Logistic Growth: Carrying Capacity Factor: % of capacity left; =▯▯  ????  100 ▯ ???????? = ???????? ???? − ???? = ????????(1 − )???? ???????? ???? ???? Assumptions: -­‐‑   “r” remains constant through time -­‐‑   All individuals are identical -­‐‑   There is no immigration or emigration (closed system) -­‐‑   There can be time lags 42.5: Immigration and Emigration Affect Population Dynamics Subpopulation: each patch of suitable habitat occupied by a species -­‐‑   Individuals may move between them Metapopulation: set of subpopulations in a region BIDE Model: adding the number of immigrants (I)/emigrants (E) to the BD growth model N = N + B + I - D - E t+1 t -   Closed Systems: no immigration/emigration; describes populations (BD Model) -   Open Systems: individuals move among subpopulations -   In BD model, extinct population remains extinct; with BIDE model, immigration can resurrect extinct 42.6: Ecology Provides Tools for Conserving and Managing Populations Understanding life history strategies can be useful in managing other species -   Conserving endangered species -   Managing fisheries o   Because fishermen prefer big fish, intense fishing reduces avg age of female fish o   Younger females were smaller and produced less eggs o   Population density rapidly declined -   Reducing disease risk o   Controlling abundance of rodents that are hosts is more effective than controlling abundance of deer Conservation begins with inventories of habitats/potential risks to habitat -   Largest patches are given priority b/c potentially have largest populations/genetic diversity -   Ability of organism to disperse between patches is evaluated -   For some species, a continuous corridor of habitat is needed to connect subpopulations à allows dispersal Exam: Ch. 23 – insects/invertebrates, chordates, chart showing major adaptations, mammals (major clades: eutherians, prototherians, etc.), not much on primates Proximate/ultimate (Behavior) Ecology vs. evolution Behavior (read/know everything in chapter 40) Population Ecology (Math!)


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