PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31EcologyUnit IVThe study of the interactions between organisms and their environmentI. EcologyA. Factors affecting distribution and abundance of a species1. Abiotic2. BioticB. Hierarchy of ecological studyII. Population ecologyA. Why study population ecologyB. Properties of populations1. Size, density, dispersion, sex ratio, age structure2. Energy allocation and tradeoffs3. Life history4. Survivorship curvesECOLOGY: Slide Set XVI8th:52.27th: 50.2In ecology, one asks: what factors influence the distribution and abundance of organisms.e.g., ask: What is causing this observed pattern?Any ideas?1. Abiotic components - nonliving chemical and physical factors2. Biotic components - living components (= all the organisms in a particular envir.)I. ECOLOGY The study of the interactions between organisms and their environment.A. Influential environmental components affect distribution & abundance of organisms in the environment:Abiotic factors: physical: temperaturehumiditylightwindsoil/substrate structurefiretopography/physical structure chemical: wateroxygenpHsalinityminerals, nutrientsBiotic 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 = 400Possible factors limiting the geographic distribution of a species8th: 52.6; 7th: 50.6This highlights the fact that ECOLOGY is a multidisciplinary field of study.(lots of factors involved)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.B. Different levels of complexity in ecology, but three predominant ones:(8th: 52.2; 7th: 50.3)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!)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 environmentExamples of types of ecosystems? (coral reef, rain forest, deserts, savannah, tundra, etc.)B. Different levels of complexity in ecology, but three predominant ones:II. POPULATION ECOLOGYA. 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 populations2.For better pest control3.To better manage populations of endangered species4.To better understand human population growth and managementBasically: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. growth1. Examples: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 in a pop’n.)a pop’n. of elephant sealsi. 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?c. pop’n. dispersion patterns:8th: 53.41. 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 foreste.g., age structures of three nations: a frequency distribution of age classesThe age structure of a pop’n. is a function of Birth rate & Death rate, & these vary with age. “Zeropop’n. growth”8th: 53.25Majority are of child-bearing age(so rapid pop’n. growth): broad baseMost are past child-bearing age (so ZPG): narrow base2. 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. Probability of # of offspring born (x) aged x survival to age x to females aged x 0 600 born 1.0 0 1 300 survive 0.5 0 2 240 survive 0.4 2 3 60 survive 0.1 3 4 30 survive 0.05 5A life table is a demographic tool to predict future pop’n. structure (e.g., insurance companies).(300/600)(240/600)(60/600)(30/600)(8th: Table 53.1)wimpy males?Example of actual long-term demographic data summarized in a life table: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
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