Organisms' Niche and Interactions: Exploring Habitat, Predation, and Symbiosis

1. 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.

2. An Organism’s Niche • unique position occupied by a species • habitat and ecological function (role) • ‘job’ of a particular species in an ecosystem

3. 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

4. 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

5. Indirect Competition • Use of same resource at different times or without direct contact • Ex: Humans and the insects that eat our food crops

6. 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

7. 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

8. 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)

9. 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

10. 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

11. 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