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a group of populations of different species living close enough to interact


___ boundaries are set by the researcher based on observed distributions;
observed patters, practical reality
most boundaries are easy to draw

natural edges

where abiotic factors change abruptly, sharp boundaries may exist between adjacent communities

natural edges

ex. river separates communities


came into focus in the 1970s
obligate (organisms can't live without each other) or facultative(can surivve without each other)?


ex. clown fish and anenome
clown fish are immune to poisonious anenome tentacles. if outside of the anemoe, clown fish gets preyed. anemone may use the food that the clown fish picks up

gut symbiosis

(mutualism) a whole range of organisms living in our guts; these organisms help you digest food. but may cause problems


(mutualism) obtains nectar, collects pollen and help the plant reproduction. however, the bee may cheat in this system because it can mate with an orchid


(mutualism) fungi gets into the cell wall of plants

nitrogen fixation

(mutualism) needs to be fixed by bacteria that lives in the plants

species diversity

includes species richness and species diversity

dominant species

a species that is numerically abundant (in individuals or biomass) and that forms a conspicous part of the community

dominant species

ex. American chestnut in American forests in the eastern side

keystone species

a species that is not necessarily abundant but that exerts strong control on community structure; puts community together

keystone species

ex. starfish for chitins, mussels, etc.
when keystone predator is absent, mussel population takes over

keystone species

ex. sea otters eats starfishs, mussels, etc
when you take the otters out of the system, urchin population booms- which removes the kelp forest

species cascade

ex. killer whales are starting to each sea otters (keystone species)

ecosystem engineers

ex. beavers physically modifies their shelthers
+ for other organsims, providing shelther for fish, ducks, etc
- for trees

facilitator species

positive effect on other species


the nonseasonal, direction, and continuous pattern of colonization and extinction on a site by species population


___ includes primary, secondary, and degradative


mechanisms include facilitation, inhabitation, tolerate

primary succession

when you start a clean, physical slate

primary succession

ex. after volcanic eruption- nothing survives. but organisms start to come back, starting brand new

secondary sucession

major distribuance: immediately after future, succession will start from a premade slate
trees and seeds and soil still intact


(succession) 1. first species to get there


(succession) 2. start to fix nitrogen (minerals for other organisms)


(succession) 3. better nitrogen fixers


(succession) 4. local climate, equlibrium system

r selected

come first, small reproductive

k selected

grow slowly, grow large, have long life span

life history strategy

r selected can eventually become k selected

r selected

many offsprings

r selected

offspring size small

r selected

maturation time short

r selected

young age at first reproduction

r selected

mortality rate high

r selected

short life span

r selected

no parental care

k selected

few number of offsprings

k selected

large offspring size

k selected

long maturation time

k selected

old age of first reproductio

k selected

low mortality rate

k selected

long life span

k selected

long parental care

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