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Transcript
Austin Brown Interactions Within Communities Definitions Community: The population living in a given ecosystem at a given time. Ecological Niche: Organism’s biological characteristics, and abiotic/biotic resources in environment Fundamental Niche: biological characteristics of organism, set of resources individuals could use under ideal conditions. Interspecific Competition: competition for same resource between different species. Realized Niche: biological characteristics of the organism and resources individuals in a population actually use under prevailing environmental conditions. Symbiosis: interactions in which two species maintain a close relationship. (parasitism, mutualism, and commensalism) Interference: aggression between individuals of different species fighting over same resource. Exploitative Competition: interspecific competition involving consumption of shared resources. May limit access to resource of other species. Resource Partitioning: avoidance/reduction in competition for same resources by different species occupying different ecological niches Mutualism: both species benefit Commensalism: one specie benefits other is unharmed Parasitism: one species benefits at the others expense Obligatory Mutualism: symbiotic relationship where neither species could survive without the other. Microparasites: parasites that is too small to see with the naked eye Macroparasites: parasites that is larger and readily visible Endoparasites: parasites that live and feed inside of the host Ectoparasites: parasites that live and feed outside of the host Social Parasites: parasites that complete their life cycle by manipulating the hosts social behaviour Austin Brown Notes Populations don’t live in isolation they interact in their community Some species need each other to survive (insects pollinating flowers) Ecological Niche Ecological niche includes what it eats/eats it, way it reproduces, temp. range, habitat Interactions between same species (intraspecific) Interactions between different species (interspecific) These two types of interaction have important role on individuals in a community Interaction Competition Predation Symbiosis Parasitism Mutualism Commensalism Effect on population Interactions can be detrimental to one or both species. Interaction beneficial to one species/lethal to the other. Interaction beneficial to one species/harmful but not lethal to other species. Interaction beneficial to both species. Interaction is beneficial to one species/harmless to the other. Interspecific Competition Competition between different species Restricts pop. growth 2 ways actual fighting or consuming shared resources Strongest competition between species that have niche overlap More niches in common the bigger the competition 1934 Russian ecologist found that the more niches two species shared the less they coexist without driving one species to extinction. (Gause’s principle/principle of competitive exclusion) Compared Paramecium aurelia and Paramecium caudatum. Species grown in separate test tubes then in the same test tube P. aurelia drove P. caudatum to extinction in test tube. Interspecific relationships can take on several forms: o Weaker population declines o One species changes food source Austin Brown o One species migrates to another habitat Causes competition to decline Resource partitioning works by using different areas for food Interspecific relationships cause species to evolve to have new abilities for getting food out of their environment These evolutions have possibly resulted in much of the biodiversity we see today Competition affects density/dispersion of populations Predation When predator population increases prey population decreases Higher prey population=higher predator population Lower prey population=lower predator population Some predator/prey populations move in a cyclical pattern where one population is slightly out of synch with the other Cycle is affected by changes in weather, presence of new prey, and changes in amount of trapping by humans Defence Mechanisms Predator/prey interactions drive prey to develop defence mechanisms Examples in plants; thorns, hooks, spines, needles, and chemicals When prey develops defence mechanisms predators develop counter-adaptations Changes through coevolution Passive defence mechanisms include hiding Active defences mechanisms cost the prey more energy than passive defence mechanisms (e.g. fleeing) Alarm calls are also used to warn fellow prey that there is a predator Some animals use camouflage to hide or bright colours to warn they are poisonous (passive) Some species mimic these abilities to help them out… o Batesian Mimicry: harmless species resemble a harmful species so that they can trick predators to not attack them (named after Henry Bates) o Mullerian Mimicry: animal species that resemble each other and are all dangerous or poisonous. This way predators learn faster not to eat things that look like them (named after Fritz Muller). Symbiosis Means “living together” (two different species live in close, usually physical contact) Three types… Mutualism, Commensalism, Parasitism Austin Brown Mutualism: Bacteria live in guts of herbivores to help break down plant products (obligatory mutualism) Humans also bacteria in their intestines to make nutients Oxpecker birds feed on back of grazing animals Nectar and insects Commensalism: Hard to classify some biologists argue existence Caribou uncover the ground helping arctic foxes find prey Remora and barnacles hitch a ride on sharks and whales to new food sources Parasitism Parasites live/eat on most nutritious areas on earth bodies of living organisms Parasites require host to live (have constant supply of nutrients) Best known cause serious human disease (malaria, schistosomiasis, and African sleeping disease) Microparasites cause diseases An example of social parasitism is the North American cowbird laying it’s eggs in other birds’ nests Symbiotic relationships show how different species interact in a community Disruption of Community Equilibrium: Stability exists when resources are sustained, populations don’t exceed carrying capacity Interspecific relations lead to biodiversity Invasive species can harm environment As human populations expand they affect animal habitats more