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Transcript
Ecological Population Dynamics Biotic potential • The maximum number of offspring an organism can produce is its biotic potential. • What keeps organisms from reaching their full biotic potential? • Environmental limits (not enough food, water, shelter or things like disease, predation). These limits are called environmental resistance. Population Growth Models Exponential model • idealized • Called “r populations” (J-curve) Logistic model • realized • Called “K populations” (S-curve) Which one happens most often? Why? Strategies to increase biotic potential • r-selected • • • • • (opportunistic) Short maturation & lifespan Many (smaller) offspring No/little parental care High death rate EX:? • K-selected (equilibrial) • Long maturation & lifespan • Few (larger)offspring; • Extensive parental care • Low death rate • EX:? Population limiting factorsEnvironmental resistance! • Density-dependent factors: • limited food water, shelter •predation • disease • Density-independent factors •weather/climate • These factors lead to K* • (*K=The max number of individuals an area can sustain/Carrying capacity) • Biotic potential vs Environmental resistance! (All life must deal with this) • Leads to adaptation More ways to increase success is to partake in Symbiosis. (2 unrelated organisms living close together.) Mutualism +/+ both species benefit Commensalism +/o one species benefits, the other is unaffected Parasitism +/- one species benefits, the other is harmed Neutralism o/o Neither organism benefits or is hurt Types of competition: • Intra-specific competition: occurs among organisms belonging to the same species. • Inter-specific competition: occurs between organisms from different species (predator-prey) Competition reduction • Resource partitioning~ species consume slightly different foods or use other resources in slightly different ways (Develop niches) • Character displacement~ sympatric species tend to diverge in those characteristics that overlap Ex: Anolis lizard sp. perching sites in Ex: Darwin’s finch beak size on the the Dominican Republic Galapagos Islands Predator/ Prey relationshipsspecial competition 5 Types of specific coloration adaptations: • Aposematic coloration – Stay away color • Batesian mimicry – copy cat, only 1 bad • Mullerian mimicry – 2 poisonous resemble one another • Camouflage – blend in • Disruptive coloring – obscures size or shape of organisms body. All organisms characteristics and behaviors lead to increased survival. We can measure those outcomes…. Survivorship curve – plot of numbers that still alive at each age • Type 1 –Death more likely at old age Type 2 –Death equally likely at all ages • Type 3 –Death more likely at young age Where would you place k selected and r selected populations? Big Changes in the system • Primary succession- going from nothing (no soil)to pioneering community to climax community. • Why would there be nothing??? – Melting glaciers – Volcanic eruptions – Landslides – Strip mines • Secondary Succession - Re-establish an ecosystem after a disturbance • What could be a possible disturbance? – Flood – Fire Geographic dispersion of a population shows how individuals in a population are spaced. • Population dispersion refers to how a population is spread in an area. (Density) Clumped dispersion Uniform dispersion Random dispersion Random Sampling • Take the area you are analyzing. Divide it into equal quadrants. • Randomly select a specific number of subdivided quadrants, count all organisms in those areas. • Add up all organisms counted, divide by # of quadrants than X by total quadrants. • 8/4=2 X16=32 • Actual = 26 • PROBLEMS? Capture mark-recapture (Lincoln-Petersen index) • In a given area, capture a specific number of organisms, mark them and release them back into the wild • Over a set amount of time, recapture a preset number of organisms and keep track of how many have already been captured. (They have marks) • Use math to estimate total population in an area. • Problems?