Student_Outline_Unit_6 starr

Student_Outline_Unit_6 starr - Population Ecology I...

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Population Ecology I. Population demographics A. Population size- Need to know to make predictions B. Population density – # of individuals of a species 1. Quadrat sample plots – # of indivd. Of as pecies/unit of measure 2. Capture-recapture- estimation; measure several plots and multiply by total # plots occupied by that space (# marked/ C. Population ___DISTRIBUTION_________________ patterns must be taken into account when estimating population density. There are three types: 1. CLUMPED 2. UNIFORM 3. RANDOM II. Population size and growth A. Gains and losses to a population 1. Gains: birth and immigration 2. Losses: deaths and emigration B. Zero population growth- gains = losses Book: ignore imm and emigr. Births=deaths 1
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C. So, what is growth? births > deaths Example population: 2,000 mice in a corn field. 1,000 mice are born in one month to these 2,000 mice. Birth rate = In this month, 200 of the 2,000 mice die. Death rate = Net growth rate (per mouse/month) = So, population growth (G) = So the population will be at ______________at the end of the first month. What will it be at the end of the second month (assuming r is constant)? D. Exponential growth model 1. Definition – unregulated growth of a population under ideal conditions 2. Curve- exponential; ‘j’-shaped; G = rN 3. Human population – has been exponential for centuries E. Logistic growth model 1. Definition – population growth is slowed by limiting factors as population size increases 2. Curve – ‘S’-shaped G = rN x (k-n)/K levels of at the carrying capacity of the environment; as population size increases and approaches ‘K’ 2
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3. Carrying capacity ‘K’ – maximum population size an environment can support; K is not constant, it can change if the environment changes Ecological footprint = ESTIMATES HOW MUCH PRODUCTIVE LAND AND WATER YOU NEED TO SUPPORT WHAT YOU USE AND WHAT YOU DISCARD Check out: www.ecofoot.org ARE YOU AN OVERCONSUMER??? III. Comparing populations: populations have different strategies for surviving long enough to pass along their genes…we can see these differences when we look at survivorship curves and life histories. A. Survivorship curves- plot of the ____% of individ__ alive at each age category over the population’s lifespan 1. Type I – high death rates for old; few offspring but good parental care (large mammals) 2. Type III – high death rates for young; lots of offspring but little or no parental care 3. Type II – intermed. Death through life (lizards, small mammals, large brds) B. Life Histories- the adaptations that influence _reproduction_ and account for the differences seen in the survival curves. 1. Life History traits : a. age of first reproductive event (sexual maturity) b. frequency of reproduction c. # offspring per reproductive event d. amount of parental care 2. Life history traits are shaped by – natural selection and are subject to evolution 3
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1. Selection for maximum reproduction = ‘r’ strategy = producing
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Student_Outline_Unit_6 starr - Population Ecology I...

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