BSC 2011 UNIT IV STUDY GUIDE Ecology 1 a Define ecology The study of interactions between organisms and their environment b How does a population differ from a community A population is a group of organisms of the same species living in a particular area a community is all the organisms that inhabit a particular area all the species c How does a community differ from an ecosystem An ecosystem is the biotic and abiotic components of a particular environment a community is only the living biotic d Please provide a specific example that exists in nature of a population a community and an ecosystem Population example species of sharks living in the ocean community example sharks dolphins rays ecosystem example sand seaweed sunlight dolphins sharks etc 2 Define demography and list several types of vital statistics used in demography The study of population vital statistics vital stats are a tool to study population growth ex Size absolute of individuals density individuals area or volume dispersion how individuals are distributed in a population 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 The age structure of a pop n is a function of birth rate death rate how these vary with age Rapid growth majority are of child bearing age rapid population growth broad base No growth most are past childbearing age narrow base 3 b be able to interpret survivorship curves Survivorship curves depict how survival varies with age Type I humans and other large mammals low death rate when young higher late in age large investment of E in caring for relatively few young most survive to max lifespan red curve Type II birds small mammals some lizards intermediate type curve and intermediate energy investments relatively constant death rate regardless of age at any age cause of death unrelated to age black curve Type III trees marine inverts fish high death rate when young but then declines for relatively few survivors little or no investment of E caring for large s of offspring few survive to max lifespan blue curve c Explain the concept of trade offs with respect to life history The life history strategy of energy tradeoffs of a species evolves over time to maximize fitness 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 Two general life history reproductive patterns semelparity and iteroparity Semelparity big bang reproduction reproduce one and die usually many offspring with a low chance of survival variable examples salmon century plants many annuals dandelions an adaptive response to a environment Iteroparity repeated reproduction throughout life usually fewer offspring brood stable environments but higher survival most mammals an adaptation to more 4 a Explain what carrying capacity is The maximum population size a particular environment can support b How does carrying capacity affect population growth In exponential growth the population continues as if there is no K carrying capacity In logistic growth population growth slows as the population reaches K When the population size is less than the carrying capacity N K the population GROWS dN dt when the population size equals carrying capacity N K there is ZPG dN dt 0 when the population size is greater than carrying capacity N K the population shrinks dN dt 5 a Explain the difference between a population that grows exponentially as opposed to one that grows logistically Unlike exponential growth with a constant rate of growth the logistic growth rate is density dependent the growth rate changes as pop n density changes A population that grows exponentially does not have a limited amount of resources so they keep growing logistically they do and the population will eventually crash when they run out of resources b Describe the shapes of the two different growth curves The exponential curve is J shaped the species just keeps increasing and the logistic curve is S shaped population grows and then slows as it reaches carrying capacity c What does the logistic equation take into account that the exponential equation does not The logistic growth equation takes into account limited resources and carrying capacity d Define the meaning of each term in the logistic growth equation Equation dN dt rN K N K dN dt change in population size K the max population size environment can handle carrying capacity N population size r per capita rate of population increase e What is the difference between r and rmax r is the per capita rate of population growth it is maximized and dependent only on the intrinsic innate reproductive capacity of a particular species rmax is a species specific intrinsic rate of increase and reflects the maximum per capita rate of increase under ideal conditions rmax used in the exponential growth equation 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 to grow in a natural environment in which there are limited resources The new population grows and feeds on resources however as resources are used up growth rates start to decline Typically the population growth slows as the population reaches carrying capacity 8 a How does a Type I survivorship curve differ from a Type III curve with respect to both age specific mortality and survivorship lifespan Type III curve species have a high death rate when young but for the few survivors it declines as they get older very few survive to max life span In the type I curve there is a low death rate when young and it gets higher with age most survive to max life span They essentially have opposite curves b Name two types of organisms exhibiting Type I survivorship and two others that exhibit Type III survivorship Type I humans elephants Type III trees salmon 9 What is the concept of maximum sustainable yield and how might you best manage a population for maximum sustainable yield The maximum sustainable yield MSY for a population is exactly equal to half of its carrying capacity to maximize pop n growth rate by harvesting back to the size where pop n grows fastest i e back
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