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BSC 2011 UNIT IV STUDY GUIDE: Ecology 1. (a) Define ecology. (b) How does a population differ from a community? (c) How does acommunity differ from an ecosystem? (d) Please provide a specific example that exists in na-ture of: a population, a community, an ecosystem. Ecology: the scientific study of the interactions between organisms and the environment; Ex: studying interaction between frogs and how they endure climate changesPopulation: is a group of individuals of the same species living in an area; population ecol-ogy analyzes factors that affect population size and how and why it changes through timeCommunity: is a group of populations of different species living in an area; community ecology examines how interactions between species, such and predation and competition, affect community structure and organizationEcosystem: is the community of organisms in an area and the physical factors with which those organisms interact; ecosystem ecology emphasizes energy flow and chemical cycling be-tween organisms and the environment2. Define demography and list several types of “vital statistics” used in demography. (b) be able to interpret age-structure diagrams for populations. (c) discuss the appearance of an age-structure diagram for a population that is growing rapidly, as opposed to one that is actually decreasing in size or experiencing ZPG (zero-population-growth). Demography: is the study of the vital statistics of populations and how they change over time-- of particular interest to demographers are birth rates and death rates; a useful way to sum-marize some of the vital statistics of a population is to make a life table- Several types of “Vital Statistics:” age, # alive at start of year, proportion alive at start of year, # deaths during year, death rate, life expectancyLife Tables: age-specific summaries of the survival patter of a population; the best way to con-struct a life table is to follow the fate of a cohort, a group of individuals of the same age, from birth until all of the individuals are dead. ZPG: occurs when the per capita birth and death rates are equal (r=0) --> (r=b-m)Exponential Population Growth: also known as geometric population growth (dN/dt = r maxN); the size of a population that is growing exponentially increases at a constant rate, result-ing eventually in a J-shaped growth curve when population size is plotted over time.3. (b) be able to interpret survivorship curves. (c) Explain the concept of ‘trade-offs” with respect to life history. (d) Explain what a species’ “life history” refers to and provide an ex-ample of two species that have different or “contrasting” life- history strategies, describing how they differ. Survivorship Curves: a plot of the proportion or numbers in a cohort still alive at each age; generally, a curve starts with a cohort of a convenient sizeLife History: the traits that affect an organisms’s schedule of reproduction and survival make up its life history. A life history entails three main variables: when reproduction begins (the age at first reproduction or age at maturity), how often the organism reproduces, and how many off-spring are produced per reproductive episode. Life history traits are evolutionary outcomes re-flected in their development, physiology, and behavior.Example: Semelparity: occurs in some plats; means 1 reproduction; favored in unpredictable environments b/c adults less likelyto survive so a lot of offspring at once should hopefully in-crease population sizeIteroparity: repeated reproduction; typically produce fewbut large offspring each time (lizards or cats); may be favored in more dependable environments, where adults are more likely to survive to breed again and where competition for resources may be intenseTrade-Offs: no organism could produce as many offspring as a semelparous species and provi-sion them as well as an interoparous species. there is a trade-off between reproduction and sur-vival. One example describes a study of birds that demonstrated a survival cost to parents that care for a large number of young. In another study, researches found that female red deer that re-produced in a given summer were more likely to die the next winter then were females that did not reproduce-- selective pressures influence the trade-off between the number and size of off-springK-selection: density-dependent selection; selection for traits that are sensitive to population density and are favored at high densitiesr-Selection: density-INdependent selection4. (a) Explain what carrying capacity is. (b) How does carrying capacity affect population growth? Carrying Capacity: symbolized by K, is the maximum population size that a particular envi-ronment can sustain-Carrying capacity affects population growth because an environment only has so many re-sources to sustain a population of such a size. Energy, shelter, refuge from predators, nutrient availability, water, and suitable nesting sites can all be limiting factors. 5. (a) Explain the difference between a population that grows exponentially as opposed to one that grows logistically. (b) Describe the shapes of the two different growth curves. (c) What does the logistic equation take into account that the exponential equation does not? (d) Define the meaning of each term in the logistic growth equation. (e) What is the difference be-tween r and rmax? -Populations that grow exponentially: J-shaped curved; (dN/dt = rmaxN); also known as geo-metric population growth; operates under ideal conditions-- a population whose member all haveaccess to abundant food and are free to reproduce at their physiological capacity-Populations that grow logistically: S-shaped; portrays changes in growth rate as the popula-tion size nears the carrying capacity; (dN/dt=rmaxN * (K-N/K) ); to construct the logistic model, we start with the exponential population growth model and add an expression that reduces the per capita rate of increase as N increases. This equation includes K-- the exponential equation does not use K. -K-N = is the number of additional individuals the environment can support-(K-N)/K = is the fraction of K that is still available for popln. growth-multiplying r max * (K-N/K) = we modify the change in population size as N increasesr = per capita rate of increaser max = maximum rate for the species6. Imagine a natural population (say a newly established small population of mice in large meadow) that is initially small in


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FSU BSC 2011 - UNIT IV STUDY GUIDE: Ecology

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