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Berkeley BIOLOGY 1B - Lecture Notes

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Lecture outlines – Part 2: Ecologyi) Densityii) Distribution (or dispersion)iii) Age Structure – organisms may change in many ways as they age, eg. food source, predators and competitors may all change.i) Life tables (death tables would be a better name)ii) Survivorship curvesi) Life history componentsii) Life history trade-offs eg. current reproduction may reduce future growth or survivorshipLecture outlines – Part 2: EcologyEcology lecture 1 - Ecology and the ecological methodA - What is Science? i) Hypothetico-deductive science: The scientific method:Making observations Forming hypotheses Making predictions Testing predictionsii) Science as a cumulative processiii) Scientific proof as an oxymoronB - What is ecology?i) Definitions of EcologyHaeckel (first definition) – the comprehensive science of the relationship of the organism to the environment.Modern consensus (e.g. Krebs 1972) – the scientific study of the interactions that determine the distribution and abundance of organismsC - Fundamental questions in ecologyi) Why are there so many species?ii) Why do the numbers of many species remain roughly constant?iii) What determines the distribution of a species?D - Introduction to Ecologyi) Individuals, populations and communitiesii) Biotic (pertaining to life or living organisms) and abiotic (non-living) factorsiii) Species distributions (relevant to global warming, invasions, genetically engineered species & habitat fragmentation)Ecology lecture 2 - Individuals - adaptation and behaviorBehavior and evolution – behavioral ecology emphasizes evolutionary hypotheses for animal behavior based on the assumption that animals increase their fitness by optimal behavior.A - Group livingi) Advantages (avoiding predation, increased feeding rate, energy gains)ii) Disadvantages (increased predation, increased competition, increased disease, increased cuckoldry, increased cannibalism)iii) Weighing up costs and benefits - an optimality approach using a common currencyA method for the non-mathematical bird - A rule of thumbB - Altruismi) Kin-selection – the importance of inclusive fitnessii) Reciprocal altruism – you scratch my back I’ll scratch yours. The importance of discrimination against cheaters.Apparent altruism may also turn out to be due to manipulation (eg. cow birds) or actual individual benefit (some alarm calls)C - Mating systems and parental carei) Some terms to know – Monogamy (prolonged pair bond), Polygamy (one or both sexes has more than one mate)Polygyny (male mates with several females who each mate with one male), Polyandry (female mates with several males who each mate with only one female), Promiscuity (both male and female mate with several partners)ii) Birds – generally limited by the rate of food delivery to the nestiii) Mammals – only females lactate often limiting the contribution by the maleiv) Fish – little parental care but when it occurs either sex could carry it out (eg. fanning eggs)v) Environmental factors affecting mating systemsThe economics of defending resources (in space and in time)Resource defence polygynyFemale defence polygynyFemale synchrony as a means to enforce monogamy John Latto 7/10/07Ecology lecture 3 - Population biology I – demography & life historyA - Population Structurei) DensityDifficulty of measuring directlyEstimation (e.g. mark-release-recapture) – assumes the proportion of marks in the second sample is equal to the proportion of marks in the population as a whole. Knowing the number marked (a) and sampled (b) in the second sample and the number initially marked (c) we can calculate the population size(d): a/b = c/d therefore d= (c x b)/aii) Distribution (or dispersion)Random (rare in nature)Regular (or overdispersed) – frequently caused by competitionClumped (or patchy) – many possible causes, distribution of resources for example.iii) Age Structure – organisms may change in many ways as they age, eg. food source, predators and competitors may all change.Comparison of human populationsGraphical presentationsB - Population Analysisi) Life tables (death tables would be a better name)Cohort – follows a group of individuals born at the same time (hard to do but accurate)Static – looks at all the individuals present during one time period (easier but harder to interpret)ii) Survivorship curves Type I (e.g. humans) – mortality is low until most individuals die late in their lifespan.Type II (e.g. some bird species) – a constant proportional mortalityType III (e.g. many insect and fish species) – most individuals die young, the few that survive may then live for much longer.C - Life historiesi) Life history componentsSemelparity vs. iteroparity (reproduce once or repeatedly)Age at first reproduction (precocity vs. delay)Clutch sizeSize as an adult (and growth rates to reach that size)ii) Life history trade-offs eg. current reproduction may reduce future growth or survivorshipEcology lecture 4 - Population biology II - growth and regulationA - Population growth in an unlimited environment - exponential growthi) Derivation of equation staring with Nt+1 = Nt+B-D+I-E (Births,Deaths,Immigrants,Emigrants)ii) Discrete time vs. continuous time – dN/dt – the population rate of changeB - Population growth in a limited environmenti) Four features of competition – between individuals, shared requirement for a resource, resource is in limited supply, leads to a reduction in vital rates)ii) Density dependencewhat it is (a necessary condition for population regulation) and what it is not (not a sufficient condition)iii) Derivation of the logistic equation: dN/dt = rN( 1-N/K)K - the carrying capacityr - the intrinsic rate of increase of the populationiv) Population density determined by:density dependent factors ANDdensity independent factorsv) Limitation vs. regulationvi) Time delays – generally lead to oscillations and instabilityvii) Life histories - ‘K’ and ‘r’ selected populationsK-selected – long lifespan, low mortality, good competitors producing few, high quality offspringr-selected – short lifespan, high mortality, good dispersers and colonizers producing many small offspring with little parental care. C - Human Population Growthi) ‘The population explosion is over’ ?ii) The demographic transition – describes the transition from high birth and death rates to low birth and death rates. John Latto


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Berkeley BIOLOGY 1B - Lecture Notes

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