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Ecology > ch. 18: community structure > Flashcards

ch. 18: community structure Flashcards

1
Q

ecotone

A
  • boundary b/w adjacent communities
  • transitional zone b/w ecosystems where there is a mix of species in both adjacent ecosystems
  • boundary created by sharp changes in environmental conditions over a relatively short distance, accompanied by a major change in the composition of species
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2
Q

interdependent communities

A

communities in which species depend on each other to exist

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3
Q

independent communities

A

communities in which species DO NOT depend on each other to exist

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4
Q

species richness

A

the number of species in community

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5
Q

relative abundance

A

proportion of individuals in a community represented by each species
- n/N
- n = number of individuals of 1 species
- N - total number of individuals of all species

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6
Q

log-normal distribution

A

normal (bell-shaped curve) distribution that uses log-scale
- on x-axis

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7
Q

rank-abundance curve

A

curve plot of relative abundance of each species in a community in rank order form most abundant species–>least abundant species

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8
Q

species evenness

A

comparison of relative abundance of each species in community

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9
Q

Simpson’s index

A

measurement of species diversity

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10
Q

key-stone species

A

species that substantially affects the structure of communities despite the fact that individuals of species might not be particularly numerous

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11
Q

intermediate disturbances hypothesis

A

hypothesis that more species are present in community that occasionally experiences disturbances than in community that experience frequent of rare disturbances

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12
Q

food chain

A

linear representation of how diff species in a community feed on each other

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13
Q

food web

A

complex and realistic representation of how species feed on each other in a community

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14
Q

trophic levels

A

level in a food chain or food web

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15
Q

primary consumer

A

species that eats producers

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16
Q

secondary consumer

A

species that eats primary consumer

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17
Q

tertiary consumer

A

species that eats secondary consumer

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18
Q

omnivore

A

species that feeds at several trophic levels

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19
Q

guild

A

w/in trophic level; group of species that feeds on similar items

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20
Q

direct effect

A

interaction b/w 2 species that does involve other species

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21
Q

indirect effect

A

interaction b/w 2 species that involves 1+ intermediate species

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22
Q

density-mediated indirect effects

A

indirect effect caused by changes in density of intermediate species

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23
Q

trait-mediated indirect effects

A

indirect effect caused by changes in traits of intermediate species

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24
Q

trophic cascade

A

indirect effects in a community initiated by predator

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25
bottom-up control
when abundance of trophic groups in nature are determined by amnt of energy available from the producers in a community
26
top-down control
when abundance of trophic groups is determined by existence of predators at top of food web
27
community stability
ability of community to maintain particular structure
28
community resistance
amnt that a community changes when acted upon by some disturbances, such as addition and removal of species
29
alternative stable states
when community is disturbed so much that species composition and relative abundance of populations in community change, and new community structures is resistant to further change
30
native
organisms naturally found in an ecosystem
31
nonnative (Exotic, alien, invasive)
any organism not found naturally in ecosystem - usually transported by humans
32
indicator
organisms that serve as early warnings of damage to a community
33
keystone species
organism has a disproportionate effect on the rest of the ecosystem - strong interactions w/ other species affect life of others - not necessarily numerous - process out materials out of proportion to numbers/biomass
34
removal of keystone species can cause...
a community to collapse
35
keystone species increase
prey diversity (and overall ecosystem diversity)
36
ecosystem engineers
keystone species that affect communities by influencing the structure of a habitat
37
communities are categorized by their...
dominant organisms - (or by physical conditions that affect distribution of species)
38
define community
assemblage of species living together in area
39
succession
communities change over time
40
community interactions
predation, competition, mating
41
most salt tolerant mangroves?
landward
42
edge effects
important aspect of community structure is the boundary b/w 1 habitat and others
43
2 types of ecotones
sharp or flat
44
types of edge effects
inherent, induced, narrow, wide, convoluted, perforated
45
wide edge effect
substantial distances separates border point where physical conditions and vegetation do not differ from interior patch
46
convoluted edge effect
border is non-linear
47
perforated edge effect
border has gaps that host other habitats
48
typically there is greater __ ___ where the edge effect occurs
species richness
49
___ surveys can demonstrate the existence of an ecotone
line-transect
50
__ changes in distribution of species should occur across the ecotone
sharp
51
interdependent communities
communities in which species depend on each other to exist - removing a species should cause other species to decline
52
independent communities
communities in which species DO NOT depend on each other to exist - removing a species should cause neutral or positive changes in other species' fitness
53
community structure
species interactions b/w 2 species at a time - combine species interactions
54
keystone species are usually the...
- top predators - ecosystem engineers
55
zonation
- zones w/ diff ranges of environmental conditions and species - reflect range of tolerance for species in zones
56
sharp boundaries (ecotones)
closed communities
57
indistinct boundaries (ecotones)
open communities
58
inherent edge effect
natural features stabilize the border location
59
induced edge effect
transient, natural, or human-related activities - subject borders to successional changes over time
60
narrow edge effect
one habitat abruptly ends and another begins
61
Clements
viewed species in a community as interdependent super organism with distinct ecotones
62
Gleason
viewed species as responding idiosyncratically to environmental gradient
63
community concepts: most research supports _____ model
Gleason's individualistic
64
abrupt changes in species distributions may be the result of...
abrupt changes in abiotic conditions
65
to plot species evenness (rank-abundance curve)...
rank most abundant species (1), next most abundant (2), etc.
66
what is biodiversity? (3 parts)
species richness, species abundance, species diversity
67
scales of biodiversity: alpha diversity
species biodiversity of local community (natural habitat patch) - w/in habitat diversity
68
scales of biodiversity: beta diversity
number of species 2 communities DO NOT share - change (or turnover) in species composition b/w 2 distinct communities - b/w habitat diversity - highest when habitats vary over fine spatial scales
69
scales of biodiversity: gamma diversity
total species richness over a large geographic area such as biome, continent, or ocean basin -measure of overall diversity for diff ecosystems w/in 1 region
70
Menhinick's index (D)
number of species divided by sqrt (number of individuals in sample) - the larger the sample, the more species you would expect - D = s / sqrt(N) - takes into account richness and evenness
71
species evenness
- quantitative measurement - measure of the abundance of individuals in each species - free from variations, equal in measure/quantity
72
simpsons index
common measure of species diversity; (ranges from 1 --> max number of species in community) - S = 1/ (summation(p^2)) - s = species richness - p = relative abundance of each species in community
73
Shannon's index (H')
H' = (-) summation (p)(ln p)
74
Simpson's index: high D value
good and means the habitat is diverse, species rich, and able to withstand some environmental impact
75
Simpson's index: low D value
poor and means that habitat is low in species, so a small change to environment would have a serious impact - ex: pollution
76
can 2 species occupy the exact same niche at the same time?
no! because of the competitive exclusion principle (one will be better)

Ecology (33 decks)

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