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This text explains the difference between niche and habitat, describes the five major types of interactions between species, and explores the concepts of parasitism, predation, and symbiotic relationships. It also discusses the ways in which species adapt to competition and the coevolutionary aspects of symbiosis.
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Objectives • Explainthe difference between niche and habitat. • Describethe five major types of interactions between species. • Explainthe difference between parasitism and predation. • Explainhow symbiotic relationships may evolve.
An Organism’s Niche • unique position occupied by a species • habitat and ecological function (role) • ‘job’ of a particular species in an ecosystem
Ways in Which Species Interact • Five major types: based on benefit / harm to the other species • Competition • Predation • Parasitism • Mutualism • Commensalism • Other types of interactions are possible • Many interactions between species are indirect
Competition • relationship between two species (or individuals) • both attempt to use the same limited resource • both are negatively affected • members of the same species must compete: same niche • different species compete when niches overlap: use some of the same resources
Indirect Competition • Use of same resource at different times or without direct contact • Ex: Humans and the insects that eat our food crops
Adaptations to Competition • advantageous for species whose niches overlap to divide up the niche in time or space • Niche restriction: each species uses less of the niche than they are capable of using • observed in closely related species in same habitat
Predation • an interaction where one species, the predator, feeds on the other species, the prey • most organisms have evolved some mechanisms to avoid or defend against predators • predators with a specific type of prey tend to increase and decrease in a linked pattern
Parasitism • Parasite: organism that lives in or on another organism and feeds on that organism • spends some of its life in or on the host • Ex: ticks, fleas, tapeworms, heartworms, leeches • Host : organisms the parasite feeds on • often weakened or exposed to disease as a result • Parasitism: relationship where parasite benefits, host is harmed (usually not killed)
Mutualism • a relationship in which both species benefit • many species depend on each other for survival • Ex: bacteria in human intestines • help us break down food we cannot digest • we provide food-rich habitat
Commensalism • relationship in which one organism benefits and the other in unaffected • Ex: sharks and remoras (a fish) • Remoras attach themselves to sharks • Feed on scraps of food left over from shark’s meals
Symbiosis and Coevolution • Symbiosis:two different organisms live in close association with each other • often used to describe a relationship in which at least one species benefits • Coevolution: species evolve adaptations that reduce the harm or improve the benefit of the relationship