ECOL 182R 1st Edition Lecture 20 Outline of Last Lecture I Black carbon tropospheric ozon II Political controversial III IPCC reports a Positive negative IV Coral reefs V Predicted impacts VI Prediction rates compared to the past a Major exctinction Outline of Current Lecture I The niche II Competition III Competition the niche IV How do so many species coexist Current Lecture The niche the total range of abiotic biotic conditions tolerated resources used Each species requires many specific resources A saguaro s niche Soil moisture tolerated Temperature range tolerated Presence of pollinators Nurse plants It s abstract not a practical concept Because the total range of conditions is never known And some species aren t where they should be Fundamental niche is the niche that potentially can be occupied Realized niche is part of the fundamental niche that is actually occupied in the presence of other species What would keep a species out of part of its fundamental niche Predators In some okay sites Competitors Monopolizing some necessary resources Competition resource use by one individual that reduces its availability for others In nature resources are limited in availability Who competes Intraspecific comp individuals of the same species competing for mates or space Interspecific comp individuals of different species competing water or space How does it happen Interference direct confrontations Dragonflies First sperm fertilizes female 2nd male to mate with female scoops out first male s sperm They re not physically fighting but one is aggressively intercepting Exploitation indirect depletion of shared resources Bats taking as much nectar as they can First bat gets the most second gets less etc Competition is a testable hypothesis Ants and rodents both eat seeds of Sonoran Desert plants Do they compete Yes if there aren t that many seeds But if seeds a hugely over abundant then no Well they have no contact Ants are diurnal rodents are nocturnal But seed use overlaps So is there interspecific exploitation competition Yes Shared resource and no physical contact You make a prediction if there is in fact competition for food number of 1 species will rise when competitors are removed Did an experiment and both species grew when the other species was kept out so yes Competition the niche Competition limits how much its fundamental niche a species can use What would happen if ALL resources were shared The worst competitor would be completely excluded Competitive exclusion principle complete competitors cannot coexist But this is a paradox Diversity of Earth is really high Some coexisting species are really similar How can this be There must be mechanisms that permit similar species to coexist Resource partitioning splitting up of shared limiting resources
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