BIO 141 1st Edition Lecture 18 Outline of Last Lecture II. Caffeine, Coffee, Tea, ChocolateIII. DepressantsIV. OpiumV. HeroinVI. CocaineOutline of Current Lecture VII. PopulationVIII. Growth RatesIX. ConservationX. FireXI. BiodiversityCurrent LectureCommunity Ecology- Biological Communities: what controls population?- Conservation: Genetics and restoration- Biodiversity: what should we do and why?- Ecosystems: How they go together and come apart.Population- Carrying capacity: the population of a species that can be supported in a specific area without depleting the available resources- Overshoot: when a population exceeds the carrying capacity of the environment and deaths result from a scarcity of resources- Population crash: a rapid dieback in the population to a level below the carrying capacity- Boom and bust: when a population undergoes repeated cycles of overshoots followed by crashesFactors Affecting Population Growth- Logistic Growth is density-dependent which means that the growth rate depends on the population densityThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Many density-dependent factors can influence a population including: disease, physiological stress and predation- Density-dependent factors intensify as population size increases- Density independent factors may also affect populations. These may include drought, fire, or other habitat destruction that affects an ecosystemFactors that Regulate Population Growth- Intrinsic factors: operate within or between individual organisms in the same species- Extrinsic factors: imposed from outside the population- Biotic factors: caused by living organisms, tend to be density dependent- Abiotic factors: caused by non-living environmental components. Tend to be density independent, and do not really regular population although they may be important in increasing or decreasing numbers. Ex. Rainfall, storms Factors that Affect Growth Rates- 4 factors affect growth rate: Births, Immigration, Deaths, and Emigration. (r=B+I-D-E)- Emigration: the number of organisms that move out of the population to another populationR and K Selected Species- R-selected species: high productive rate, but high mortality rate with little or no paternalcare (mice and insects)- K-selected species: few offspring, slower growth as they near carrying capacity and exercise more parental care (elephants)Conservation Genetics- In a large population, genetic diversity tends to be preserved. A loss/gain of a few individuals has little effect on the total gene pool- However, in small populations small events can have large effects on the gene pool- Genetic drif: change in gene frequency due to a random event- Founder effect: few individuals start a new population- Demographic bottleneck: just a few members of a species survive a catastrophic event such as a natural disaster- Founder effects and demographic bottlenecks reduce genetic diversity. There also may be inbreeding due to small population size.Helping Nature Heal- Ecological restoration: to reverse degradation and reestablish some aspects of an ecosystem that previously existed- Restoration to an original pristine condition is rarely possible. Ofen the best option is to choose an alternative condition with desirable characteristics. Sometimes as entirely new use for the site is the best alternative.Recognizing the Role of Fire- Land managers now recognize the role of fire in maintaining/restoring many forest typeso Superior National Forest in Minnesota has started a program of prescribed fireso Can also allow natural fire to burnRestoring Prairies- Before European settlements, the eastern edge of the Great Plains was covered by tall grass prairie, with grasses reaching a height of 2 mo Less than 2% remains- The middle of the Great Plains contained a mixed prairie of bunch and sod-forming grasses- The western edge of the Great Plains, with less rainfall, was covered by grassFire is also Crucial to Prairie Restoration- In 1934, Aldo Leopold begun to re-create tall grass prairie on an abandoned farm in Madision, WI.o Discovered that fire was essential. Kills weeds and removes soil nitrogen, which gives low-nitrogen native species an advantage- Nature Conservancy has tall grass prairie northwest of Tulsa, OKo 1/3 of each pasture burned per yearBiodiversity- Economic Arguments (wheat)o Undiscovered productso Ecosystem