Community Ecology Relationships Between Organisms AP Biology

Ecological Niches A species' niche includes: Habitat - where it lives in the ecosystem Relationships - all interactions with other species in the ecosystem Nutrition - its method of obtaining food

Competition Competition = when two species compete for the same resource Competition can lead to competitive exclusion or resource partitioning

Competitive Exclusion Competitive Exclusion Theory –2 species cannot occupy the same niche –If 2 species occupy the same niche, then they will compete until one eliminates the other (becomes extinct)

Resource Partitioning If one species’ niche is modified through natural selection, then it will be able to coexist with the other species (that it competed with before). –niche differentiation –Modified use of resources

Character Displacement Is evidence of previous competition between species Allopatric Speciation = speciation that occurs in species that are geographically isolated from each other Sympatric Speciation = speciation that occurs in species that live in the same area

Character displacement How does the diagram show evidence of competition? When the populations live together, character displacement occurs in order for the populations to co-exist (sympatric speciation)

Animal Defenses: Aposematic coloring Coloring or markings to warn off predators

Animal Defenses : Cryptic coloration Coloring that disguises an animal’s shape

Animal Defenses: Batesian Mimicry A species mimics a successful species but lacks the actual attribute– “pretending to be harmful” Scarlet king snake harmful Not harmful

Müllerian Mimicry Monarch butterfly Viceroy butterfly A species resembles another successful (harmful) species and shares the attribute (is also harmful)

Plant Defenses Against Herbivory Thorns and spines Glandular hairs –store and secrete toxins Deposition of crystals in plant tissues – makes tissues tougher Chemical compounds –May be distasteful or toxic to animals –May cause abnormal development in animals Images taken without permission fron and

Summary of Species-Species Interactions Competition-/- Predation+/- Herbivory+/- Parasitism+/- Disease (Pathogen)+/- Mutualism+/+ Commensalism+/0

Keystone Species species that has a strong influence on its ecosystem. –Ex. Sea otters, prairie dogs If it is not there  will cause populations of other species in the ecosystem to go down or become extinct; Can drastically change the ecosystem even though it isn’t the most abundant species. –Dominant species = most abundant species Images taken without permission from and