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 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 changes Population 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 time Community 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 organization Ecosystem 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 environment 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 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 expectancy Life 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 size Life 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 to crease but in likely Example Semelparity occurs in some plats means 1 reproduction favored in unpredictable environments b c adults less likely survive so a lot of offspring at once should hopefully in population size Iteroparity repeated reproduction typically produce few large offspring each time lizards or cats may be favored more dependable environments where adults are more to survive to breed again and where competition for resources may be intense Trade 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 spring K selection density dependent selection selection for traits that are sensitive to population density and are favored at high densities r Selection density INdependent selection 4 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 have access 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 increases r per capita rate of increase r max maximum rate for the species 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 If we were to look at a
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