BSC 2011 UNIT IV STUDY GUIDE Ecology 1 a Define ecology Ecology the study of the interactions between organisms their environment In ecology one asks What factors influence the distribution and abundance of organisms What is causing this observed pattern Population ecology Concerned with the characteristics of a population such as its growth rate size density age structure sex ratio and how these characteristics change in response to ecological and evolutionary pressures What factors affect population size age structure and distribution through space and time the study of population growth Why study better manage crop and livestock populations for better pest control to better manage populations of endangered species to better understand human population growth management Community ecology How do interactions between populations of different species that live in the same area affect the structure and organization of a community Ecosystem ecology What are the interactions between a biotic community in an area and its abiotic physical environment How do nutrients energy flow through communities in an ecosystem b How does a population differ from a community Population is a group of organisms of the same species co occurring in time space Community is all the organisms inhabiting a particular area all the species The community consists of multiple populations of different species c How does a community differ from an ecosystem Ecosystem is the biotic abiotic components of a particular environment Biotic components living components all the organisms in a particular environment Predation interactions between different species competition interactions within a species density disease parasitism type of predation Abiotic components nonliving components and physical factors Physical temperature humidity light wind soil substrate structure fire topography physical structure Chemical water oxygen pH salinity minerals nutrients The community is all of the species and organisms the ecosystem is the interactions in the community and the nonliving and chemical factors d Please provide a specific example that exists in nature of a population a community an ecosystem Population Rabbits in the desert Community A desert community consists of rabbits coyotes snakes birds mice and such plants as cacti brush ect Ecosystem Coral reef the biotic is the species of fish and corals the abiotic is the salinity of the water pH what minerals and nutrients are there oxygen levels physical structure of the coral reef the amount of light temperature of the water etc 2 a Define demography and list several types of vital statistics used in demography Demography the study of population s vital statistics and the factors that influence these Vital statistics are a tool to study population growth 1 Population size absolute number of individuals 2 Population density number of individuals area or volume 3 Population dispersion how individuals are distributed in a population 4 Population sex ratio male female even or skewed 5 Population age structure the distribution of different age classes in a population Even everything is the same age e g trees in a planted garden Mixed different ages in a population e g tress in a natural forest b Be able to interpret age structure diagrams for populations Age structure of a population is a function of birth rate death rate and these vary with age 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 Rapid growth majority are of child bearing age diagram has a broad base Afghanistan Slow growth relatively even distribution of ages percent of the population starts to decrease after age 50 United States No growth most are past child bearing age zero population growth ZPG diagram has a narrow base Italy 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 Cohort a group of individuals born at the same time Life table an age specific summary of survival for a population obtained by following a cohort through life Shows how birth rate and death rate varies with age A life table is a demographic tool to predict future population structure b Be able to interpret survivorship curves Survivorship curves survival as a function of age depicts how survival varies with age Not always clear cut for many species Type 1 humans and other large mammals Low death rate when young higher late in age Few young most survive to maximum lifespan High E investment Type 2 birds small mammals some lizards Intermediate type curve and intermediate E investments Relatively constant death rate regardless of age at any age Cause of death unrelated to age Type 3 trees marine inverts fish High death rate when young but then declines for the relatively few survivors Little or no investment of E caring for large s of offspring c Explain the concept of trade offs with respect to life history An organism has a limited amount of E energy to allocate to enhance its fitness survival and reproduction Tradeoff any E expended to one of these needs takes E away from other functions usually a trade off between survival reproduction Therefore E allocation takes on a complex cost benefit ratio to the organism Characteristic patterns of energy allocation evolve over time for a species Species evolve different life history strategies to maximize fitness Semelparity big bang reproduction reproduce once and die usually many offspring with low chance of survival Often an adaptive response to a variable environment Salmon century plants many annuals dandelions Iteroparity repeated reproduction throughout life usually fewer offspring brood but higher survival An adaptation to a more stable environment Most mammals 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 Life history a species specific pattern of birth reproduction and death use demographic data to compile a LH for a particular population Life history traits examples age of first reproduction frequency of reproduction length of reproductive activity number of offspring per brood or episode Tradeoffs between E needed for survival vs reproduction shape a species life history over evolutionary time Species evolve
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