BSC 2011 UNIT IV STUDY GUIDE: Ecology 1.(a) Define ecology. (b) How does a population differ from a community? (c) How does a community differ from an ecosystem? (d) Please provide a specific example that exists innature of: a population, a community, an ecosystem. Ecology: study of the interactions between organisms and their environmentPopulation vs community: populations are a group of organisms of the same species occurring in time and space. Communities are all the organisms in a particular area (all different species)Community vs ecosystem: communities are all of the different kinds of species in one particular area. Ecosystems are the communities AND the biotic (living components) & abiotic (nonliving components) of a particular environmentExample of population: size, density, and dispersion of animals that are the SAME SPECIESExample of community: species richness (total number of different species) and the relative abundance (the proportion each species represents total community)2.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: the study of population vital statistics and the factors that influence these “vital stats”: population size, density, dispersionage structure diagrams: a function of birth rate and death rate and vary with age rapid growth: looks like a triangle. Broad base. Most population is young age. slow growth: looks pretty even. Population is pretty steady no growth: zero population growth. Narrow bases. 3.(a) What is a cohort? What can a person learn from a “life table” and a “reproductive table”that has been constructed for a particular population of some species? (b) be able to interpret survivorship curves. (c) Explain the concept of ‘trade-offs” with respect to lifehistory. (d) Explain what a species’ “life history” refers to and provide an example of two species that have different or “contrasting” life- history strategies, describing how they differ. cohort: group of individuals born at the same time life table: an age specific summary of survival for a populationinterpreting survivorship curves: they change varying with ageType 1: (humans/large mammals): low death rate when young. Have few young, most surviveType 2: (birds, small mammals, lizard): constant death rate regardless of age. The cause of death is not because of ageType 3: (trees, marine inverts): high death rate when young but then declines. Few offspring survivetrade-offs: any E expended to one of these needs takes E away from other functions. (survival vs reproduction)** tradeoffs between E needed for survival and for reproduction shape species life history over evolutionary time**life history: it refers to a species-specific pattern of births, reproduction, and death semelparity: reproduce once and then die. Have many offspring with low chance of survival. “big bang reproduction”, adaptive to variable environment iteroparity: repeated reproduction throughout life. They have less offspring but they survive more. (mammals) They adapt to stable environments. 4.(a) Explain what carrying capacity is. (b) How does carrying capacity affect population growth? Carrying capacity: (K)= the maximum population size a particular environmentcan supportCarrying capacity affects population growth: resources are limited in the real world. Population growth rates will decline when resources are used up and when population grows. Resources in environment get used up as population increases in size. 5.(a) Explain the difference between a population that grows exponentially as opposed to onethat 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 between r and rmax? Exponential growth: growth rate is constantly growingLogistic growth: growth rate changes depending on density. Growth rate will slow as the population increasesExponential growth shape: J shapeLogistic growth shape: s shape (sigmoid)The logistic equation takes into account that there is only a certain amount of resources that people can survive on and that there is a carrying capacity in the environment.Logistic growth equation: dN/dT=rmaxN [(K-N)/K] the part that is added to the logistic growth equation that is not apart of the exponential growth equation is (K-N)/K. This term modifies growth rate, R. as N increases, resources diminish.Rmax vs r: Rmax: species specific intrinsic rate of increase and reflects the maximum per capita rate of increase under “ideal” conditions. R: overall rate of population increase as a function of (birth rate- death rate)6.Imagine a natural population (say a newly established small population of mice in large meadow) that is initially small in size and that will proceed to grow logistically. Describe how the rate at which this population grows changes over time as it continues togrow in a natural environment in which there are limited resources. The small population of mice in the large meadow will proceed to growexponentially at first when it is introduced because there is so much land and resources. However, resources are limited in the real world. Soon, the populationgrowth rates will decline because there will not be enough resources to sustain the population. When there are no more resources, growth rates decline. And maybe death rates increase if they cannot adapt to the limited resources.7.What is the difference between density-dependent and density-independent factors that regulate population growth? Please give an example of each. Density- dependent: if a factor of birth rate or death rate changes in response tochange in population density extrinsic DD regulating factors (environment):- limited resources- predation- accumulation of waste intrinsic DD regulating factors (biological)- crowding effectDensity- independent: if birth and death rates change, but it does not have to do with population density. hard to predict changes in population- weather- sudden catastrophes8.(a) How does a Type I
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