UNIT IV STUDY GUIDE Ecology influence these i Vital Statistics 1 Define ecology a Ecology the study of the interactions between organisms and their environment How does a population differ from a community b A population is a group of organisms of the same species co occurring in time and space but a community includes all of the organisms inhabiting a particular area all the species How does a community differ from an ecosystem c A community includes only the biotic components of a particular area all the species but an ecosystem is all of the biotic and abiotic components of that particular environment 2 Define demography and list several types of vital statistics used in demography the study of population vital statistics and the factors that a Demography tools used to study population growth 1 Population size absolute number of individuals 2 Population density number of individuals per area or volume 3 Population dispersion how individuals are distributed in a population Be able to interpret age structure diagrams for populations b Age Structure vary with age for a population a function of birth rate and death rate and these 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 c An age structure diagram for a population that is growing rapidly will have a wide base and narrow out to a point at the top pyramid or triangle shaped but a diagram showing a population decreasing in size or experiencing ZPG will have a narrow base and remain about the same width all the way up 3 Be able to interpret survivorship curves a Survivorship Curve i Three types a demographic tool that shows survival as a function of age 1 Type I humans and other large mammals low death rate when young higher late in age large investment of energy caring for relatively few young most survive to max lifespan 2 Type II birds small mammals some lizards intermediate type curve and intermediate energy investments relatively constant death rate regardless of age at any age i e cause of death unrelated to age 3 Type III trees marine inverts fish high death rate when young but then declines for the relatively few survivors little or no investment of energy caring for large numbers of offspring few survive to max lifespan Explain the concept of trade offs with respect to life history b A trade off is when energy is expended to one need and therefore taken away from other functions The trade off is usually between survival and reproduction His trade off shapes a species life history over evolutionary time For example is less energy is invested into survival and more into reproduction the organism will generally life fast and die young But if more energy is invested into survival than reproduction by living longer the organism can produce enough offspring to maintain the species 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 of an organism a species specific pattern of birth reproduction c Life History and death i Semelparity many offspring with low chance of survival big bang reproduction reproduce once and die usually 1 salmon century plans many annuals dandelions ii Heroparity offspring brood but higher survival repeated reproduction throughout life usually fewer 1 Most mammals elephant horse panda bear lion humans 4 Explain what carrying capacity is a Carrying Capacity can support K the maximum population size a particular environment How does carrying capacity affect population growth b Population growth is a function of the carrying capacity of a particular environment Population growth rates will decline as resources are used up when a population grows 5 Explain the difference between a population that grows exponentially as opposed to one that grows logistically a A population that grows exponentially has a constant growth rate with an unlimited environment and resources The per capita rate of population growth is maximized and dependent only on the innate reproductive capacity of a particular species The pattern of the graph is J shaped On the other hand is a population that grows logistically This population slows its growth rate as the population size increases slowly reaching the carrying capacity of the environment The growth rate of this population changes with density The pattern of this graph would be S shaped Describe the shapes of the two different growth curves b The shape of the exponential curve will be J shaped and the logistic curve will be S shaped What does the logistic curve equation take into account that the exponential equation does not c The logistic curve equation takes into account the carrying capacity of an Define the meaning of each term in the logistic growth equation environment K N K d dN dt rN K N K i d deaths ii N population size iii t time r per capita rate of population growth iv v K carrying capacity What is the difference between r and rmax e Plain r is simply the per capita rate of population growth but rmax reflects the maximum per capita rate of increase under ideal conditions It is the species specific intrinsic rate of increase 6 Imagine a natural population say a newly established small population of mice in a 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 a Because there is some carrying capacity present in this environment the population of mice will at first grow at a relatively fast rate Population growth will slow as the population continues to grow in size as the population reaches its carrying capacity As the population hits the carrying capacity the number of mice will decrease until more resources become available for the population to continue growing again You would most likely see a cyclic pattern 7 How does a Type I survivorship curve differ from a Type III curve with respect to both age specific mortality and survivorship lifespan a In a Type I survivorship curve usually humans and other large mammals there is a low death rate when young and most survive to the maximum lifespan But in a Type III survivorship curve trees marine inverts fish there is a high death rate when young and few survive to the
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