1. Understanding PopulationsSection 2 Objectives Explain the difference between niche and habitat. Describe the five major types of interactions between species. Explain the difference between parasitism and predation. Explain how symbiotic relationships may evolve.

2. Understanding PopulationsSection 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. Understanding PopulationsSection 2 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. Understanding PopulationsSection 2 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. Understanding PopulationsSection 2 Indirect Competition Use of same resource at different times or without direct contact –Ex: Humans and the insects that eat our food crops

6. Understanding PopulationsSection 2 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. Understanding PopulationsSection 2 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. Understanding PopulationsSection 2 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. Understanding PopulationsSection 2 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. Understanding PopulationsSection 2 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. Understanding PopulationsSection 2 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