Life in a Community
An ecological community consists of all the populations of different species that live and interact in a particular area. Interspecific interactions are the relationships between different species in a community.
Major Interactions
Competition (-/-): Occurs when two or more species compete for the same limited resource (e.g., food, water, space). It is a negative interaction for both species.
The competitive exclusion principle states that two species competing for the same limiting resource cannot coexist permanently in the same place. One will eventually outcompete and eliminate the other.
Predation (+/-): An interaction in which one species, the predator, kills and eats the other, the prey. This includes herbivory (an animal eating a plant).
Symbiosis: An ecological relationship in which two species live in close physical contact with each other. There are three main types.
Types of Symbiosis
1.Mutualism (+/+): An interspecific interaction that benefits both species.
Example: The relationship between flowering plants and their pollinators (bees get nectar, plants get pollinated). The relationship between nitrogen-fixing bacteria and legume roots.
2.Commensalism (+/0): An interaction in which one species benefits and the other is neither harmed nor helped.
Example: Barnacles attaching themselves to a whale. The barnacles get a ride and access to filter-feeding opportunities, while the whale is largely unaffected.
3.Parasitism (+/-): An interaction in which one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process.
Example: A tapeworm living in the intestines of a mammal. The tapeworm gains nutrients, while the host loses them.