Observations Review October 30 2009 Bio 1b Ecology section The only way truly new information is acquired Good natural history Consistent long term monitoring Nowadays Advanced mapping sensing and tracing technologies Experiments Field or laboratory replicated manipulated treatments with controls Whole ecosystem experiments lake fertilization Hubbard Brook deforestation Models verbal or mathematical simplifications of reality intended to capture key processes that change systems over time Hypotheses suggested explanations subject to test falsifiable 1 Patterns that demand explanation Marine intertidal grazing halos snails take cover in mussels and venture into patch to graze algae but only go so far from cover 2 Tools for dealing with ecological variability Replicates are separate independent units of study that are treated identically by ecologists in order to assess variability that arises from factors we didn t manipulate Controls are unmanipulated units that provide a baseline for comparison an understanding of how organisms or systems will change over space or time independent of experimental treatments Statistics tools for distinguishing signal from noise e g test whether differences between treatments e g control vs experimental are greater than differences within treatments 3 Meadow food web response to doubled rainfall and changed seasonal timing 4 These factors set up global moisture patterns Wet tropics around equator Deserts at 30 o N S latitudes Temperate rain forests at 60 o N S latitudes 5 Fig 50 25 Campbell Antarctic and artic deserts at poles 6 Coriolis effect Earth is a sphere not a cylinder An object at equator is moving east at 24 000 miles per day As it moves north the earth beneath moves more and more slowly so it veers right If it moves from north towards equator it also goes right because Reverse is true in southern hemisphere Northeast trade winds pile the Atlantic against Central America Earth rotates west to east How do conditions and resources influence the distribution and abundance of organisms Return flow is the Gulf Stream7 Resources conditions and the fundamental niche What determines the distribution and abundance of species In part their tolerance of conditions and their need for certain resources Niche Range of conditions resource levels and densities of other species within which an organism or species can survive and reproduce persist over time An N dimensional hypervolume hypervolume if each condition resource or other species seen as a dimension Hutchinson Fundamental Niche the largest niche in which a species could persist in the absence of adverse interactions with other species Realized Niche the generally smaller niche volume occupied by a species in the presence of interspecific interactions condition abiotic environmental factor that varies in space and time and affects the performance of organism resource all things consumed used up by organisms space nutrients water prey holes for refuge etc 8 9 10 Prediction Salt 30 ppt Observation present Salinity Realized stickleback niche if gill parasite is present Without parasite Realized Niche with gill parasite tolerates narrower range of conditions Fresh 0 ppt absent Dispersal limitation Enemies o Response variable 11 Insufficient resources Intolerable conditions N hot spot o o Temperature Subsidies Sinks Relicts Sufficient resource Tolerable conditions H1 Gills damaged so can t osmoregulate as well H2 Parasites take energy so less to spend on osmoregulation absent present o o o o o Grazing hot spot Predictor variable s e g PAR 12 Definitions unitary Life history Tradeoffs modular Relict population Residual population left over from time when environment Sequoia could support its survival and redwoods reproduction which can no longer replace itself locally Sink habitat Habitat where death rates exceed birth rates and organisms are present only because of immigration from Source Habitats where births exceed deaths Currencies energy nutrients time Spotted owl Barred owl Resource subsidy Resources produced in one habitat that support consumers in a second habitat Allocation growth 13 activity maintenance Reproduction offspring quality offspring quantity 14 Beach wrack seaweed detritus New northern limit with high food New northern limit with low food Where starvation presently affects bass population bass Current range perch High food Low food Now 15 16 Campbell Fig 52 13 density dependence in per capita birth and death rates due to intraspecific within species competition Campbell Fig 52 11 K carrying capacity of population in a given environment K depends on both the environment and the organism in question 17 Per capita per individual birth or death rates Northern range expansion of small mouth bass and yellow perch predicted based on predicted climate warming scenarios The bottleneck for both fish is whether the young of the year can grow large enough to survive their first winter 18 Population overshoot Change in limiting factor Territoriality can produce population growth that approaches a stable equilibrium e g speed limit versus regulation by enforcement of minimum and maximum speed N Density independent factors 19 Period of looser regulation Time 20 r vs K selected life history traits r selected traits K selected traits Short life span Small size High predator vulnerability Weak competitor Good disperser Many small offspring Early reproduction Long life span Large size Low vulnerability to predators Strong competitor Slower disperser Fewer but better provisioned offspring Late reproduction 21 22 Balanus upper limit determined by physical stress Chthamalus lower limit determined by competition with Balanus Functional definitions 23 24 3 Types of Competition Exploitative two species compete for a resource that is limiting in short supply relative to their needs indirect Interference two species directly harm each other by toxic allelochemicals injury or wasting time increasing risk etc direct Enemy mediated Apparent two species decrease in each other s presence because they support the increased abundance or vigor of a common predator parasite or pathogen indirect 3 species interactions Mutualists and cheaters Cleaner wrasses host fish cheater blennies Milkweed bee cheater orchid Pollinator moth bumblebee nectar burglar Selection for refinement of cues and mimicry in co evolutionary race How much cheating can be tolerated before mutualism breaks down 25 26 Trophic level functional
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