Interactions in Ecosystems Chapter 14 Interactions in Ecosystems

Habitat and niche Habitat-all biotic and abiotic factors in the environment where the organism lives Niche-physical, chemical, and biological factors a species needs to survive Habitat = where; niche = how

Competitive exclusion The principle of two species competing for the same resources and resulting in one species gaining the advantage The other species can be pushed into another niche or possibly become extinct Could also result in Niche partitioning (different parts being used) Evolutionary response (divergent evolution)

Ecological equivalents Species that occupy similar niches but in different geographical regions Different regions means they DON’T compete for the same resources

Symbiosis Close and permanent relationship between different species 3 types Commensalism Mutualism parasitism

Commensalism One species benefits but the other is neither helped nor harmed Ex: peregrine falcon and red-breasted goose

Mutualism Both species benefit Ex: lichen (green alga and a fungus)

Parasitism One species benefits and the other is harmed Harmed species does not die Benefiting species lives off tissues of the host

Population density Population density-measurement of the number of individuals in a defined space or area Can be used to determine the health of the population and ecosystem Population dispersion indicates how species interact within the ecosystem

Survivorship curve Generalized diagram showing surviving members of a species over time from a measured set of births

Survivorship curve

Survivorship types

Population growth Change in size of a population over time Studied by bacterial growth No linear growth Have “J” curve growth cycles Exponential growth Population explosion Reaches carrying capacity; “S” curve

Exponential growth Occurs when individuals in a population reproduce at a constant rate Population becomes larger over time

Logistic growth Slowing or stopping of population growth after a period of exponential growth Due to reduction in resources

Growth curves

Limiting factors Density-dependent Density-independent Increased effect as population increases Include disease, competition, parasites Density-independent Affect all populations regardless of size Abiotic factors like temperature, drought, flood, habitat disruption

Mobility Immigration-movement of individuals into a population Emigration-movement out of a population

Succession Natural changes that take place in the communities of an ecosystem 3 types Primary Secondary climax

Primary succession Colonization of new sites by organisms First organisms are pioneer species Example: Forming new plant and animals colonies on volcanic rock

Secondary succession Changes in a community that occur after disruption by a natural disaster or human interference Takes less time than primary succession to reach climax

Climax succession A mature community that undergoes little or no succession All species in the community have reached their peak