Post-Exam 2: W12D1 Community Ecology Flashcards
know environmental biology? as I am doing with stats
metapopulation
Non-continuous, connected (by gene flow!) populations characterized by
frequent extinction and colonization events
Often source-sink dynamics
It is NOT a “population of populations”
Community Structure
The kinds and relative abundance of
species in each community
(community structure): Species Richness
number of
species in a given area (usually for
same taxonomic group like plants)
(community structure): species evenness
combines both
species richness and relative
abundance of each species
Communities with more species, and
the numbers of those species are
more even (similar numbers) are
considered to be more diverse
Determining community structure
(species interaction): commensalism
+, 0
an association between two organisms in which one benefits and the other derives neither benefit nor harm.
(species interaction): amensalism
0, -
the two-species interaction in which the impact of one species on the other is negative, but where there is no detectable impact of the second species on the first
0, -
(species interaction): competition
-,-
an interaction between organisms or species in which both require a resource that is in limited supply (such as food, water, or territory)
(species interaction): mutalism
+,+
(species interaction): parasitism
+,-
(species interaction): herbivory
+,-
(species interaction): predation
+,-
food web: trophic interactions (tell me them from bottom to top)
Bottom to top:
also below is decomposers (mushrooms)(detritivores: consume dead and decaying organic matter known as detritus to obtain energy and nutrition)
primary producers (the plants, berries)(autotrophs-an organism that can produce its own food using light, water, carbon dioxide, or other chemicals)–>
primary consumers (the bison, elk, beaver)(heterotrophs-an organism that eats other plants or animals for energy and nutrients) –>
omnivores(bear, raven, coyote)–>
secondary and tertiary consumers(gray wolf, weasel)(heterotrophs)
biotic
living things within an ecosystem; such as plants, animals, and bacteria
abiotic
non-living components; such as water, soil and atmosphere
bottom up determinants of community structure
bottom up factors (a lower trophic level that affects community structure of higher trophic levels by means of resource restriction):
* Drought years
* Change the nutrient availability (N, P, etc.)
* These changes in primary producers influence all the
trophic levels above them
top down determinants of community structure
(species occupying the highest trophic level (top carnivores) exert a controlling influence on species at the next lower level (their prey) and so forth down the trophic ladder)
– Change in predator affects whole community
(Yellowstone – wolves)
– Trophic cascades
species that outsized roles for community structure
- Dominant species: most common
○ Communities named for them
(often, not always) - Foundational species: species that
other species grow on or depend on;
often dominant species
○ Eg, the trees in a forest, giant kelp,
corals - Ecosystem engineers: species that
influence community structure by
creating/modifying their environments - Eg, beavers, elephants
- keystone species (next card)
keystone species
Species that
have a disproportionate effect on
community structure based on their
abundance
e.g: Sea otters eat sea urchins
sea urchins eat kelp
no otters, no kelp
no kelp, no many, many other
species
just to know: trophic levels & energy transfer
only abt 10% of each level’s absorbed energy is absorbed by the next one
disturbance impacts on community structure
- Disturbance: any event that removes biomass from a community.
– Either natural or anthropogenic
– Vary in frequency and intensity - Disturbance regime: typical frequency and intensity of
disturbances for a community.
how fires can increase diversity
- Release nutrients
- Open space/reduce
competition - Reduce shading
- Limits herbivory
