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Ecology > community > Flashcards

community Flashcards

1
Q

what is community

A

group of species living in a given area in competiton mutualism or predation

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2
Q

attributes of a community

A

species number
relative abundance
physical structure
interactions among species

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3
Q

relative abundance

A

p(i) = n(i)/N
p(i): proportion of individuals of species i
n(i): # of individuals of species i
N: total #of all species

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4
Q

how to examine relative abundance

A

rank aboundance diagram (rank abundance vs relative abundance)
the longer(more richness) and straighter (greater evenness) the better: more diverse
info on:
species richness (S): number of species
species evenness (E): how equally they are distributed

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5
Q

diversity in a community (not richness) 1 formula

A

simpsons diversity index (D)

D = sum(p(i)^2)

value between 0 and 1

-> 1 - D : reciprocal
the higher the better

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6
Q

diversity in a community 2 formula

A

shannon index H

H = -sum(p(i)*ln(p(i))

minimum value : 0 (one species present)
max : ln(S) total # of species present

E = H/Hmax for measure of evenness

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7
Q

dominant species normal?

A

yes!!

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8
Q

what is important in a forest?

A

biomass and abundance!
few trees on the ground make not much
many big trees are important

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9
Q

species that has disproportionate impact on community compared to abundance

A

keystone species
modifies or creates habitats (coral)
elephant destroys trees -> more space for grass -> more food for small herbivores and habitats
removal can have leathal impact for community

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10
Q

flow of food

A

food chain:
grass to preditor
describes flow of energy from bottom to top
grass -> grasshopper -> sparrow -> hawk
these chains get very complicated very quickly
-> simplification needed

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11
Q

feeding group in food chain

FACHBEGRIFF

A

trophic levels

lvl1: primary producers 1000pds (phytoplankton)
lvl2: 1st order consumer 100pds (zooplankton)
lvl3: intermediate predators 10pds (grouper)
lvl4: top predator 1pds (shark)

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12
Q

new form of classification

A 
functional types (rather function than taxonomic group)
based on:
THE ROLE IN THE COMMUNITY
response to environment
life history charcteristics
role within the community

example plants:
shade tolerant and intolerant

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13
Q

physical structure of community

A

reflect abiotic (light, wind, ect.) and biotic (size, density,…) properties

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14
Q

physical structure of healthy forest?

A

multiple layers of vegetation

in mediterranian for example no ground layer -> water lack

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15
Q

layers in aquatic communities

FACHBEGRIFF

A

photic layer
aphotic layer
benthic layer (bottom) can be photic and aphotic

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16
Q

consumer placement in community

A

they are not restricted to one level.

can move vertically through forest or water (zooplankton)

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17
Q

what is good for community diversity?

A

environmental heterogeneity

more layers -> more living spaces and food -> more diversity

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18
Q

change in physical and biological structures across landscape
(FACHBEGRIFF)
example

A

zonation

tree community changes greatly while moving up the mountain
bottom: 17 species top: 3 species

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19
Q

defining communities?

A

is difficult… mostly a continous drift
vary with objective of study ect…
but dominant species are a good measure

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20
Q

condition for species to survive

A

there is a min and an optimum

defined by the niche

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21
Q

realized and fundamental niche

bigger or smaller

A

realized niche can be bigger (mutualism) or smaller (competition)

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22
Q

differences in species tolerance lead to?

FACHBEGRIFF

A

zonation

shifts in relative abundance

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23
Q

competitive vs. toleration

A

competitive species:
higher growth rate however not so tolerant
tolerant species moves away from competitive species

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24
Q

competition effects of certain species on community

removal of competitor?

example hare

A

some species depend on competition with one species, other on comp. with many

can have very different effects (small or large)

the hare only benefits if many preditors die out

25
Q

competitive effects of a number of interspecific competitors

FACHBEGRIFF

A

diffuse competition

diffuse interaction -> not that important for the other competitor -> indirect interaction

26
Q

top-down-control (yellowstone)

A

wolves eat dears -> deers hide -> less plants eaten -> more birds / less erosion -> better riverbanks -> whole physiological appearance changes

27
Q

down top control (ocean)

A

abundance of photoplancton -> fish -> big fish

28
Q

restore condition in community or ecosystem before human interference
ubranisation ect.
(FACHBEGRIFF)

A

RESTORING ECOLOGY
reintroducting species
restoring habitats
reestablishing communities

29
Q

reestablish native species on degraded cropland

A

destroying present bushes
reseeding and replanting native species
burning the site every two or 3 yearrs
after 80 years community is back:)

30
Q

bad example of reestablishing

solution?

A

fear of woodland -> bad for waterbirds:
big herbivores introduced to eat seed and small trees -> population grew fast and had nothing to eat anymore -> they all starved after harsh winter
a cooridor to island to allow migration and release stress if necessary
also no preditors

31
Q

if a predator suppresses abundance of herbivore and favours plant growth (example)

A 
trophic cascade (influence on further trophic levels)
top down or down top
32
Q

important to know for restauration:

A

feeding habits, processes in communities, species interaction, regulation processes

33
Q

steps on abandoned cropland

A

grass -> bushes -> small pines -> canopy of trees -> big trees (maples)

34
Q

temporal change in a community structure

FACHBEGRIFF

A

SUCCESSION

35
Q

big ass trees

A

decidous or evergreen hardwoods

need shadow to grow

36
Q

a point in time in evolution of community
sequence of communities seen in succession
(FACHBEGRIFF)

A

seral stage (some times years or decades)
some stages can be missed or altered
sere

37
Q

succession example in rocky algal community

A

waves overturn rock (nat. disturbance) -> cleared surfaces -> new species colonized as there were before

38
Q

pioneer species characteristics

FACHBEGRIFF

A

early successional species

  • high growth rate
  • small size
  • high rate of dispersal -> rapid colonialzatio
  • high rate of per capita population growth
39
Q

late species characteristics

FACHBEGRIFF

A

late successional species

  • longer lifespans
  • larger size
  • lower rates of dispersal
  • low rates of per capita growth
40
Q

new hampshire tree succession

A

decidous trees died in lack of shade
herbaceous species started to dominate
they provided shade and big trees came back

41
Q

community occupies new place

A

primary succession (algal rock, lava fields, newly exposed glacial till)

42
Q

community occupies an arleady occupied space

A

secondary succession (new hampshire)

43
Q

a series of sites within an area that are at different successional stages
(FACHBEGRIFF)

A

chronosequence

44
Q

primary succession example (glacier)

A

glacier exposes new surface -> shade intolerant species like alder and cottonwood colonize -> then late successional plants like spruce and hemlock replace early ones

45
Q

three primary plant strategies

evolution through succession

A

R (ruderal):
rapid colonization, resources allocated to reproduction, wide dispersal
C (competitive):
need abundant ressources, mainly allocated to growth,
S (stress):
stress-tolerant, ressources allocated to maintenance, habitats with limited ressources

with time:
R -> C -> S

when trigger for secondary succession -> R colonize quickly, can use all types of ressources -> biomass increases -> competition occurs -> competitive C plants dominante -> on the long run S plants dominate as resistant to all sorts of stress

46
Q

ecological vs physiological charac. of early and late successional plants

A

light and water availabilty vs. seed dispersal, storage and germination

47
Q

compete for light or nutrients

A

light: carbon allocation in leaves and stems
nutrients: carbin allocation in roots

48
Q

environmental change as result of activities of organisms

FACHBEGRIFF

A

AUTOGENIC

light gradient through forest

49
Q

environmental change as result of physical change of space

FACHBEGRIFF

A

ALLOGENIC

temperature change

50
Q

diversity over succession

A

peaks at the transition from early to late successional species and stabilizes in the end at a lower level

51
Q

influence of growth rate on diversity

A

if faster -> less diversity

if slower -> process of coexisting is longer (late and early)

52
Q

cuts in succession through disturbance

A

if frequent disturbances -> no late successional species arrive -> never high diversity
if intermediate disturbances -> high diversity as succession enters transition stage
if no disturbances -> forests get old and in late stages low diversity

53
Q

animals ect in succession

A

depend on stages of succession:
grassland species: meadow mouse, grasshopper sparrow
shrubland species: squirrel, deer
forest animals: fox, ..

54
Q

influence of abiotic environ. changes on succession

A

fluctuation occur annualy (temp. and precipitation)
these dont influence pattern of secondary succession to much
but large timescale changes (climate change) are likely to influence -> change that occur at intervals in the timespan of organsims life

55
Q

(FACHBEGRIFF)

study of distribution & abundance of ancient organisms

A

Paleoecology

56
Q

sources for information of paleoecology

A

fossils: bones, insect exoscelets, plant impression and pollen grains

57
Q

human influence on community dynamics

A

when americans colonized 1600s -> dominance by forests

  • > forests cleared for agriculture
  • > now reforestation (secondary succession) -> all forests are very young
58
Q

tilmans hypothesis of succession

A

in beginnig, light availability high and nitrogen low
in end, light availability low and nitrogen high
this leads to change in succession

Ecology (11 decks)

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