Ecological Community Ch 27 l niche defines place and role of each species in an Tuesday November 17 2015 7 17 PM Ecological Community all interacting populations in an ecosystem Interactions between populations in a community help limit their size populations are kept in balance with their resources Community interactions shape the evolution of the species in that community Coevolution occurs when two species share close interaction Mutual influence on each other s evolutionary adaptations Each serve as agent of natural selection What are the effects of Competition among species Ecologica ecosystem Adaptations reduce the overlap of ecological niches among coexisting species competition helps control population size and distribution Ecological Niche Encompasses all aspects of a species way of life including physical home or habitat physical and chemical environmental factors necessary for survival how species acquires its energy and materials All other species with which it interacts Competition Among Species Interspecific competition 2 or more different species attempt to use the same limited resources Each species is harmed as access to resources is reduced The greater the overlap of ecological niches the more intense the interspecific competition Reduction of Niche overlap Competitive Exclusion principle No two species can inhabit exactly the same ecological niche simultaneously and continuously if this occurs one species will out compete the other for resources When two species with similar requirements coexist each typically occupies a smaller niche than they would individually Called resource partitioning reduces interspecific competition Predatory prey interactions shape evolutionary adaptions Coevolution Predators have evolved characteristics that increase their chances of catching prey Prey have evolved characteristics that decrease the chances of being eaten Camouflage Camouflage renders animals inconspicuous even when in plain sight May include evolved colors patterns shapes that may resemble one s surroundings To avoid detection some animal species have evolved to resemble objects such as bird droppings leaves or thorns Some plants species have evolved to resemble rocks to avoid detection by herbivores Camouflage also helps predators ambush their prey Bright Colors Some species have evolved bright warning coloration that attracts the attention of potential predators Aposematic coloring Advertises they are distasteful or poisonous before the predator attacks Examples poison arrow frogs Coral snakes and yellow jackets Protection through mimicry Mimicry refers to a situation in which one species has evolved to resemble another organism Biological mimicry provides important support for evolutionary theory mimicry is a survival strategy and is explained by natural selection M llerian Mimicry Two or more distasteful species may each from a shared warning coloration pattern Predators experience one distasteful species learn to avoid all with that color pattern Example bees hornets and yellow jackets share black and yellow stripes Example monarch and viceroy butterflies share orange and black pattern Batesian Mimicry Some harmless prey organisms gain selective advantage by resembling poisonous species Trick predators into avoidance Example harmless hoverfly resembles bee Example non venomous mountain king snake resembles venomous coral snake Example harmless hawkmoth larva resembles green parrot snake Protection through Mimicry Some prey animals deter predators by employing startle coloration Have spots that resemble large eyes False eyed frog Peacock moth Swallowtail butterfly caterpillar Also bright or white patches that can be flashed suddenly Predatory Mimicry Aggressive mimicry predator resembles a harmless animal or object to lure prey within striking distance not just lying in wait for prey but actively aggressively trying to lure capture Example frogfish dangles a false wriggling lure to attract a curious fish Chemical Warfare Both predators and prey have evolved toxic chemicals for attack and defense spiders poisonous snakes venom plants chemicals to deter herbivores bombardier beetle sprays hot chemicals from its abdomen Co evolutionary Adaptations Some animals evolve ways to detoxify plant chemicals allowing them to eat the plant monarch butterfly milkweed chemicals make monarch distasteful to its predators What is Symbiosis Living together close interaction between organisms of different species for an extended time 3 major symbiotic relationships Commensalism Parasitism Mutualism Symbiotic Relationships Commensalism One species benefits and the other unaffected example barnacles hitching a ride on the skin of whales Parasitism parasite benefits but host is harmed Examples tapeworms fleas and disease causing organisms Intense Coevolution of Parasites Hosts Example the malaria parasite strong selective pressure for humans to carry defective hemoglobin gene that causes sickle cell anemia Heterozygotes have only mild sickle cell anemia symptoms but provide some protection against malaria Succession Usually preceded by a disturbance event disrupts ecosystem either by altering community abiotic structure or both Primary 1 succession no trace of previous community Secondary 2 some traces of previous community are left behind Stages of succession Begins with arrival of hardy invaders called pioneers alter ecosystem in ways that favor other species often progresses to relatively stable diverse climax community Recurring disturbances set back progress maintain communities in subclimax stages Climax Community Climax species narrower niches than pioneer species allows many species to coexist without replacing one another tend to be larger and long lived than pioneer species Biome Climax community of characteristic plants that exists over a broad geographical range Subclimax State Subclimax communities Tallgrass prairies that once covered northern Missouri Illinois periodic fires prevented forest from encroaching Suburban Lawns Mowing herbicides keep weeds woody species in check Succession in ponds lakes Lakes ponds form when disturbance blocks flow of river or stream Nutrient influx sediment deposition etc Convert body of water into bog then to dry land community