BSC 2011 Spring 2013 Unit IV Study Guide 1 a Define Ecology Ecology is the study of interactions between organisms and their environment b How does a population differ from community The difference being that the population consists of just a signal species and the community consists of a group of species and their interactions c How does a community differ from ecosystem Populations of different species living and interacting in an area form a community whereas ecosystems consist of nonliving abiotic and living biotic components 2 a Define Demography Demography is the study of population vital statistics Examples of this are population size density and dispersion b An age structure diagram of a population is a function of birth rate and death rate and varies with age An age structure diagram that is experiencing a lot of growths will display a broad base and the majority of people are of childbearing age An age structure diagram of a population with no growth has a narrow base and most of the people are past childbearing ages Image 1 Age Structure Diagrams see above 3 a What is a cohort A cohort is a group of individuals born at the same time A life table depicts an age specific summary of survival for a population It shows how birth and death rate varies with age It is useful for predicting future population structure b Tradeoffs are when an organism chooses between putting more energy into survival or reproduction Organisms have a limited amount of Energy to allocate to enhance its fitness More energy put into reproduction for example takes away energy from survival c Life History A species specific pattern of birth reproduction and death Examples of life history traits are age of first reproduction frequency of reproduction length of reproductive activity and number of offspring per brood or episode Generally there are two general life history reproductive patterns Semelparity is when an organism reproduces once and dies usually leaving behind many offspring with low chances of survival eg Salmon century plants dandelions Iteroparity is when an organism has repeated reproduction throughout life usually leaves behind less offspring but with higher survival rates eg Most mammals 4 a Carrying capacity is the maximum population size a particular environment can support b Carrying capacity affects population by limiting the amount of reproduction and survival As birth rates get closer to the carrying capacity food sources start running out and organisms will start to die 5 a A population that grows exponentially is usually a population with no restrictions or carrying capacity This is usually seen when a species is re introduced into a protected area However a population that grows logistically is growing within terms of the carrying capacity This kind of growth is density dependent and based on how many resources are available in the given environment of a population b The curve of an exponential growth graph is J shaped and continues upwards continuously The curve of a logistic growth graph is S shaped and levels off as the carrying capacity is reached c The logistic equation takes into account a limited amount of resources also known as the carrying capacity d In the logistic equation K is the carrying capacity N dN dt rmax N K N K is the population size rmax is the species specific intrinsic rate of increase e The rmax value is species specific intrinsic rate of increase and reflects the maximum per capita rate of increase under ideal conditions The r value though is the overall rate of population increase as a function of birth rate minus death rate r b m 6 This population will increase rapidly at first as all of the resources are abundant and plentiful for the population Soon though it will reach the carrying capacity and deaths will increase as the resources run out 7 Density dependent factors change in response to changes in population density Some extrinsic examples environmental are resource limitation predation and accumulation of wastes Some intrinsic biological examples are crowding effect hormonal changes depression of immune system and increased aggressive behavior Density independent growth factors affect the population but not in proportion to density Some examples are weather or random catastrophes 8 a Type I survivorship curves demonstrate long lifespans and a large investment of energy in caring for few offspring Most survive to maximum lifespan Type III survivorship curves have a high death rate of young There is litter or no investment of energy for caring for numerous offspring Few survive to the maximum lifespan b Type I survivorship curves are ideal for humans and other large mammals like bears Type III survivorship curves are ideal for fish and marine invertebrates 9 Maximum Sustainable Yield is theoretically the largest yield or catch that can be taken from a species stock over an indefinite period Managing a population for maximum sustainable yield can be done by harvesting back to the size where population grows fastest i e back to where the slope of the logistic curve is steepest 10 Why is it more sensible to clean up your kitchen than to kill off a roach population Cleaning your kitchen removes the resources for the roach population to grow and prosper Therefore you lower the carrying capacity for that population and decrease its rate of survival 11 An ecological footprint is equivalent to the demands a person places on their environment in terms of resources used and waste produced It is measured in hectares person ha person A carbon footprint also deals with resource usage but focuses strictly on the greenhouse gases released due to burning of fossil fuels 12 The four types of 2 species interactions are 1 Mutualism This is when both parties benefit from the relationship An example is seen in the relationship between cleaner fish and their clients Shrimp and fish often clean dangerous marine animals gills and teeth The cleaner fish and shrimp get a free meal while their clients get a reduced parasite load 2 Commensalism This is when one species benefits while the other species is unaffected An example is seen in cattle egrets and cows The cows disturb insects on the ground while they are grazing and the egrets eat these insects 3 Predation When one species benefits by killing and or eating another species An example is when animals eat plants herbivory 4 Competition When individuals attempt to utilize the same resources There are two types of
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