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General Ecology > Community Dynamics > Flashcards

Community Dynamics Flashcards

1
Q

What is community?

A

group of populations sharing the same area and potentially interacting

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2
Q

What are community dynamics?

A

change in community structure (abundances of different populations)

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3
Q

What is disturbance?

A

disruption of population, community, or ecosystem structure, or changes resources,
substrates, or the physical environment.

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4
Q

What is succession?

A

repeatable changes in community structure following disturbance

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5
Q

What affects succession?

A

internal (intrinsic) and external (extrinsic) forces

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6
Q

What are internal (intrinsic) forces?

A

biotic interactions within and among the populations produce
predictable change

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7
Q

What type of succession results from internal forces?

A

autogenic

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8
Q

What is external (extrinsic) forces?

A

abiotic factors that produce predictable community change

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9
Q

What type of succession results from external forces?

A

allogenic

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10
Q

What happens first 10 years after fire?

A
  • annual plants peak soon after a fire, then decline
  • followed by grasses and forbs, and finally by shrubs and pine saplings
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11
Q

What happens mid-succession after fire?

A

-by about 15 years pines reach peak density and from then on dominate
- annuals, grasses, and forbs decline while shrubs slowly increase

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12
Q

What happens late succession after fire?

A
  • after 75 years, pine densities gradually lower as trees die from self-thinning and overall biomass of trees level off
  • closed canopy keeps other plant groups at low levelW
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13
Q

What is reached during late succession?

A

dynamic equilibrium

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14
Q

Are early succession species like r or K selected?

A

like r-selected species (or Ruderal or Stress Tolerant).

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15
Q

What are characteristics of early successional species?

A

Rapid dispersal, rapid growth, short life, tolerant of extreme conditions, but easily out-competed

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16
Q

Are late successional species like r or K selected?

A

like K-selected species (or Competitive)

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17
Q

What are characteristics of late successional species?

A

Slower dispersal, slow
growth, long lives, can out-compete early colonists.

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18
Q

What are drivers in Connel/Slayter’s models of succession?

A
  • facilitation
  • inhibition
  • tolerance
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19
Q

What does facilitation drive?

A

primary and secondary succession

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20
Q

What does inhibition drive?

A

secondary succession

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21
Q

What does tolerance drive?

A

secondary succession

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22
Q

What is primary succession?

A
  • early colonizers (after a catastrophic disturbance) change
    conditions making it less favorable for themselves, and more favorable for later colonists.
  • Predictable linear sequence: Early -> Mid -> Late
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23
Q

What is secondary succession?

A

less catastrophic disturbances create a heterogeneous
patchwork in time and space, so early, mid, and late colonizers can all coexist in the same
community.

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24
Q

What is inhibition?

A
  • any plant already present can have a negative affect on any potential
    colonist
  • Only death or decay allows a later colonist to occupy the same spot
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25
Q

What is tolerance?

A

early arriving species have no effect on later arriving species, but late
successional species can out-compete early successional species

26
Q

What is initial floristic composition?

A

Many patterns are
possible, depending upon which plants get to empty (disturbed) sites first

27
Q

For equilibrium dynamics, what is a stable climax community reached via?

A

autogenic change

28
Q

What are non-equilibrium dynamics?

A

allogenic changes due to external factors (weather and climate
change, disturbance) prevent a climax community from developing

29
Q

What is disturbance regime?

A

ore or less predictable disturbance pattern (e.g., fire every so
many years)

30
Q

Species subject to predictable disturbance…

A

adapt features that allow them to persist in the
face of disturbance (e.g., fire tolerance in species with frequent fires)

31
Q

What is Connell’s Intermediate Disturbance Hypothesis?

A

intermediate levels of disturbance produce highest level of overall diversity

32
Q

What species grow well in frequent or large scale disturbances?

A

only goof colonists and rapid growing species

33
Q

What species grow well in rare or small scare disturbance?

A

only most competitive

34
Q

What are top predators?

A

not eaten alive by other predators

35
Q

What are ecosystem engineers?

A

feeding and other behaviors modify environment in substantial ways

36
Q

What are the two hypothesis for aspen decline in Yellowstone?

A
  • fire suppression hypothesis
  • elk herbivory hypothesis
37
Q

What is the fire suppression hypothesis?

A

assumed lack of fire allowed other species to outcompete aspen

38
Q

What is the elk herbivory hypothesis?

A

increases in elk herd, due to decline of wolves, reduced aspen

39
Q

What is bottom-up control?

A

resource availability determines structure of communities

40
Q

What is top-down control?

A

top of food chain controls lower down species

41
Q

What is a behavioral cascade example?

A

Reintroduction of wolves to Yellowstone deterred elk from feeding in areas where aspens
were, which increased aspens

42
Q

What is an example of predation risk and the ecology of fear?

A

presence of owls reduced gerbils’ use of open habitats

43
Q

What are autogenic ecosystem engineers?

A

physically change the environment by their own bodies

44
Q

What are allogenic ecosystem engineers?

A

physically change the environment by directly or indirectly
manipulating other living and dead organisms

45
Q

What is productivity hypothesis?

A

more productive ecosystems have more trophic levels

46
Q

What is ecosystem size hypothesis?

A

physically larger ecosystems have more trophic levels

47
Q

What is productive space hypothesis?

A

both factors play a role

48
Q

What is resistance?

A

lack of species losses in the face of disturbance

49
Q

What is return time?

A

time to recover species losses after disturbance

50
Q

What is resilience?

A

ability to recover to near the original state after disturbance

51
Q

What is persistence?

A

long-term stability of community structure

52
Q

What is constancy?

A

amplitude of variability in community structure over time

53
Q

What are alternative stable states?

A

different stable community structures are possible in a given site

54
Q

What are hypotheses for why some communities are more stable?

A
  • diversity hypothesis
  • food web connectiveness hypothesis
  • keystone species hypothesis
  • dominant species hypothesis
55
Q

What is diversity hypothesis?

A

more species-rich communities change less (are more resistant to change or are more productive)

56
Q

What is food web connectiveness hypothesis?

A

food webs with more connections are more resilient

57
Q

What is keystone species hypothesis?

A

single species strongly influences interactions among other
community members, so diversity is kept high

58
Q

What is dominant species hypothesis?

A
  • single abundant species is relied upon as a resource by many
    species, so diversity is kept high.
  • Also called a foundation species.
59
Q

species whos CI is very high in comparison to their relative abundance are

A

keystone species

60
Q

What are exotic species?

A

not originally part of the community (alien species)

61
Q

What are invasive species?

A

an exotic species that can achieve high abundances upon introduction; can impact
other species.

General Ecology (16 decks)

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