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Lecture

BIOL215 Lecture 22 Notes.pdf

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Department
Biology (Sci)
Course Code
BIOL 215
Professor
Neil Price

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BIOL215 Lecture 22 Notes A classic question in ecology first posed by Andrewartha and Birch in 1954 is what is the relationship between species distribution and abundance The pattern shows that most species have fairly small range sizes and that fairly few species have large range sizes. This pattern can be seen for birds, plants, or even animals, all showing the same distribution Rapoport's rule shows that geographic range size of particular taxa increases with latitude. What that shows is that in low latitude regions, range size of mammals tend to be small and in high latitude regions, range size of mammals is almost a factor of 10 larger, so much greater range Range size on a map is really looking at the geographic area that encompasses the perimeter of a species' habitats Rapoport's rules don’t apply to all species or situations. The ecological explanation includes climatic variability (greater at high latitudes, organisms should have greater tolerance to temperature survival), product of glaciation (as glaciers retreated, new habitats became available and the organisms who lived close to ice edge now could disperse and move into the new habitat - only organisms who could disperse to greatly can go to new habitat), lack of competition in polar communities (species diversity is much lower in polar than tropical habitat, thus competition is less intense which does not force species to occupy a portion of the range which they would otherwise occupy) Topography (mountains vs. lowlands) interacts with latitude in affecting range size Range size and population - abundance are positively correlated - Hanski's Rule. Essentially, the greater the population abundance, the greater the range size and vice-versa What mechanism is responsible for generating the positive relationship between distribution and abundance: • Sampling issue (if abundance is low, it's difficult to observe those rare individuals in nature so it's hard to determine the range in comparison to more abundant species) • Ecological specialization (some species are specialists. They use one or two resources and can occupy only a narrow range of environmental conditions. Other species are generalists who have multiple resources and can occupy a wide range of environmental conditions. You also have species in between specialist and generalist • Local population model (populations exist as metapopulations which are separated one from the other in a matrix of habitat that is inhospitable - those species which can traverse and disperse across the inhospitable region to a hospitable region have more range size because they are able to sample a much larger area) Read chapter 22 Sun energy is what drives the operation of ecosystem. Sun energy is taken through photosynthetic organisms (autotrophs) --> converts to chemical bond energy which are eaten by herbivores which are eaten by carnivores. However, some of the energy from the primary producers is used by decomposers and at each step, some of the energy is lost as waste through heat Nutrients through decomposers will be recycled for primary producers Ecosystem - a biological community plus all of the abiotic factors influencing that community Tansley (1935) - considered organisms and their environment as an integrated system Ecosystem ecologists study the flows of energy and the cycling of water and nutrients in ecosystems (not interested in the organisms per se: just their functional roles) The boundary of an ecosystem could be at the large geographic scale of a biome (large geographic areas which share similar precipitation and temperature and are defined by the predominate plants that inhabit the area). The boundaries are really set by the investigator so long as we consider the community and abiotic factors it influences The continuous free supply of energy can be from the sun (heat and light energy) or if an organism is deep in the ocean, it gets chemical energy from hydrothermal vents The transfer of energy between one level to the next will always have a loss in energy (as heat) because of the 2nd law of thermodynamics which states that no conversion is 100% efficient As autotrophs are using energy, they have to make biomass (more tissues) and in order to do so; they need a lot of elements to make proteins, enzymes, and cellular constituents. These elements all come from rocks. The earth is a closed system of material and nutrients but is an open system with respect to energy. The elements on the earth right now is not replenished for the most part and thus there must be a cycling of elements so they do not get tied down to one form. Nutrients cycle, energy flows which comes from heterotrophs' waste Primary productivity is the rate of capture of energy (sunlight) by ecosystems (primary producers - photosynthesis). Rate of energy capture (productivity) is measured as kcal/unit area/unit time, or Watts/m
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