Ch.16-Community Dynamics Flashcards
Physical caracteristics
Aquatic community - have to be in water
Dry community- only certain organisms can live there
Community
a group of interacting species that occur together at the same place and time
Biological characteristics
Coral- built a habitat in an ocean
tree- creates a community
Taxonomic subsets (1)
all the species in one taxonomic group w/in the community
Ex: birds
Guilds (2)
a group of organisms that make their living in similar ways
Ex: herbivores, seed eater, pollen eater, fungivores
Functional Types (3)
a group of species with similar morphological, physiological, behavioral, biochemical, or environmental characteristics/ responses
- don’t necessarily use the same resources
ex; aphids and mosquitos
trophic levels (4)
a group of species that obtain energy in similar ways
Food Web
a summary of the feeding relationships within an ecological community
Subdividing communites
4 main ways 1-taxonomic subsets 2-Guilds 3-Functional types 4-Trophic level
How to measure food webs
- watch interactions occur
- examine stomach contents
- examine waste contents
- determine if known prey is present and assume it eaten
- analyze stable isotopes of predator tissue
Food web representaions
trophic relationships(=who eats who) in all or part of a community -can be species, functional groups, taxonomic groups
Community food web
trace an entire set of trophic interactions within a community
Interaction web
describes both trophic (vertical) and non-trophic (horizontal) community interactions
Species interactions
the strength of interactions among species may very from pair to pair
-ex; kangaroos eating grass vs. ant eating grass
interaction strength
the degree to which one species affect another
- can be calculated, but is difficult to calculate for entire community
- requires experimental manipulation
How to quantify interaction strength:
interactor and target: cage an area and remove interactor
-Large change in target abundance=strong interaction
Indirect interactions: Mutualism
(acacia tree and ant mutualism)
Indirect interactions: competition
Interference competition: Species A (-)->resource<-(-/+) Species B
~indirect interactions between species A and B
Indirect interaction: Competition
Apparent competition: Occurs between two prey species eaten by the same predator(s)
~ex: snails and clams are both eaten by ocutpus
Some species have very large effects on whole communites
Large interaction strength
-can be direct or indirect
Dominant Species
- Tend to be larger and or extremely abundant
- may provide habitat or food for other species
- may be good competitors for space, nutrients, or light
Keystone species
-Found in relatively low abundance and low biomass
-Have a disproportionate effect on community structure
~Ex: sea stars, sea otters, jaguars, beavers, elephants, prairie dogs
Types of keystone species
- Keystone Predators (ex: sea otters)
- Keystone food resource (Ex: Figs)
- Keystone habitat modifier (ex: Beavers)
- Keystone ecosystem processor (ex: Decomposers)
Trophic interactions
Involve direct and indirect interactions-Can be:
Bottom-up or Top-Down
