Unit IV Ecology The study of the interactions between organisms and their environment ECOLOGY Slide Set XVI I Ecology A Factors affecting distribution and abundance of a species 1 Abiotic 2 Biotic B Hierarchy of ecological study II Population ecology A Why study population ecology B Properties of populations 1 Size density dispersion sex ratio age structure 2 Energy allocation and tradeoffs 3 Life history 4 Survivorship curves In ecology one asks what factors influence the distribution and abundance of organisms e g ask What is causing this observed pattern Any ideas 8th 52 2 7th 50 2 I ECOLOGY The study of the interactions between organisms and their environment A Influential environmental components affect distribution abundance of organisms in the environment 1 Abiotic components nonliving chemical and physical factors 2 Biotic components living components all the organisms in a particular envir Abiotic factors physical temperature humidity light wind soil substrate structure fire topography physical structure chemical water oxygen pH salinity minerals nutrients Biotic factors predation interactions between diff species competition interactions within a species density if you have a lot of biological animals condensed in a single area disease parasitism a type of predation iClickers What limits seaweed abundance Figure 52 8 8th edition Answer Mostly urchins Indicative of biotic reactions Mark Release Recapture method of estimating population size Total population size to estimate N initially captured and marked m recaptured total n of recaptured that were marked x If you initially trap and mark 80 raccoons then after a week you recapture 20 raccoons of which 4 were marked what is N total population size for raccoons in this forest 400 m N x n 80 N 4 20 So N mn x N 80 20 4 1600 4 400 Possible factors limiting the geographic distribution of a species This highlights the fact that ECOLOGY is a multidisciplinary field of study lots of factors involved 8th 52 6 7th 50 6 B Different levels of complexity in ecology but three predominant ones 8th 52 2 7th 50 3 1 Population ecology What factors affect population size age structure and distribution through space and time Population a group of organisms of same species co occurring in time and space 2 Community ecology How do interactions between populations of different species that live in the same area affect the structure and organization of a community Community All the organisms inhabiting a particular area i e all the species B Different levels of complexity in ecology but three predominant ones 3 Ecosystem ecology a What are the interactions between a biotic community in an area its abiotic physical environment b How do nutrients and energy flow through communities in an ecosystem An ecosystem the biotic abiotic components of a particular environment Examples of types of ecosystems coral reef rain forest deserts savannah tundra etc II POPULATION ECOLOGY A 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 Why study pop n ecology hint think of populations of specific kinds of organisms people might want to study 1 To better manage crop and livestock populations 2 For better pest control 3 To better manage populations of endangered species 4 To better understand human population growth and management Basically pop n ecol is the study of population Growth B Studying the properties of populations Demography the study of pop n vital statistics see examples below the factors that influence these i e vital stats are a tool to study pop n growth 1 Examples in a pop n a pop n SIZE absolute of individuals b pop n DENSITY individuals area or volume c pop n Dispersion how individuals are distributed or dispersed a pop n of elephant seals c pop n dispersion patterns i if CLUMPED ask Is this the result of envir factors food there Is this indicative of social structure wolves Does clumping increase survival ii if UNIFORM ask Is this the result of individuals interacting e g aggressive territoriality iii if RANDOM ask Is this dispersion pattern shaped to chance 8th 53 4 1 Types of vital statistics cont d d male female Sex Ratio even e g 50 50 skewed e g 90 female 10 male e Age structure the distribution of different age classes in a pop n can have an EVEN age structure e g trees in a planted plantation can have a MIXED age structure e g trees in a natural forest The age structure of a pop n is a function of Birth rate Death rate these vary with age e g age structures of three nations a frequency distribution of age classes 8th 53 25 Zero pop n growth Majority are of child bearing age so rapid pop n growth broad base Most are past child bearing age so ZPG narrow base 2 A LIFE TABLE an age specific summary of survival for a pop n obtained by following a COHORT a group of indiv born at the same time through life shows how birth rate and death rate varies with AGE Age of indiv x aged x Probability of survival to age x of offspring born to females aged x 0 1 2 3 600 born 300 survive 240 survive 60 survive 1 0 0 5 0 4 0 1 300 600 240 600 60 600 30 600 0 0 2 3 30 survive 4 A life table is a demographic tool to predict future pop n structure e g insurance companies 0 05 5 Example of actual long term demographic data summarized in a life table wimpy males 8th Table 53 1 II B Properties of pop ns cont d 3 ENERGY E allocation an organism has a limited amount of E to allocate to enhance its fitness survival reproduction any E expended to one of these needs takes E away from other functions a tradeoff usually a trade off between survival and 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 A tradeoff example cost of parental care on parents survival Kestrals a bird 8th 53 9 Different strategies for the tradeoff between E for reproduction and E needed for survival to maximize FITNESS tree sparrow Sparrow less E invested in survival more E into reprod reproduce earlier and at a higher rate annually to produce enough offspring to perpetuate the species Live fast die young Albatross more E into survival than annual reproduction by living longer can produce enough offspring to maintain the species Fig 52 5 albatross albatross Two very different strategies of energy allocation at the extremes both
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