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ECOLOGY > Community Ecology > Flashcards

Community Ecology Flashcards

1
Q

A community’s structure can be described by its

A

species richness

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2
Q

the number of species present

A

species richness

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3
Q

is a measure of both species richness and species evenness (relative numbers)

A

species diversity

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4
Q

Community structure is influenced by many factors, including:

A

abiotic factors, species interactions, level of disturbance, and chance events.

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5
Q

play particularly important roles in determining their communities’

A

foundation species and keystone species

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6
Q
  • is the feeding relationships between organisms in a community
  • It is a key factor in community dynamics
A

Trophic structure

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7
Q

link trophic levels from producers to top carnivores

A

Food chains

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8
Q

is a branching food chain with complex trophic interactions

A

Foods Webs

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9
Q

Food webs can be simplified by

A
  • Grouping species with similar trophic relationships into broad functional groups
  • Isolating a portion of a community that interacts very little with the rest of the community
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10
Q

Each food chain in a food web is usually only

A

a few links long

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11
Q

Two hypotheses attempt to explain food chain length

A

the energetic hypothesis and the dynamic stability hypothesis

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12
Q

suggests that length is limited by inefficient energy transfer.

For example, a producer level consisting of 100 kg of plant material can support about 10 kg of herbivore biomass.

A

energetic hypothesis

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13
Q

the total mass of all individuals in a population

A

biomass

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14
Q

proposes that long food chains are less stable than short ones

A

dynamic stability hypothesis

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15
Q

Most data support the _______ hypothesis

A

energetic hypothesis

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16
Q

highly abundant or play a pivotal role in community dynamics

A

Species with a Large Impact

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17
Q

are those that are most abundant or have the highest biomass

A

Dominant Species

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18
Q

_______ exert powerful control over the occurrence and distribution of other species

For example, _______ have a major impact on shading and soil nutrient availability in eastern North America; this affects the distribution of other plant species

A

Dominant Species; sugar maples

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19
Q

One hypothesis suggests that ______ are most competitive in exploiting resources

Another hypothesis is that ______ are most successful at avoiding predators

A

dominant species

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20
Q

typically introduced to a new environment by humans, often lack predators or disease

A

Invasive species

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21
Q

exert strong control on a community by their ecological roles, or niches

A

Keystone Species

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22
Q

In contrast to dominant species, they are not necessarily abundant in a community

A

Keystone Species

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23
Q

Field studies of _____ illustrate their role as a keystone species in intertidal communities

A

sea stars

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24
Q

Is an event that changes a community

Removes organisms from a community

Alters resource availability

A

A disturbance

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25
Q

Is a significant disturbance in most terrestrial ecosystems

Is often a necessity in some communities

A

Fire disturbance

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26
Q

Suggests that moderate levels of disturbance can foster higher species diversity than low levels of disturbance

A

The intermediate disturbance hypothesis

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27
Q

Demonstrated that communities can often respond very rapidly to a massive disturbance

A

The large-scale fire in Yellowstone National Park in 1988

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28
Q

Are the most widespread agents of disturbance

A

Humans

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29
Q

Usually reduces species diversity

A

Human disturbance to communities

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30
Q

also prevent some naturally occurring disturbances.

Which can be important to community structure

A

Humans

31
Q

Is the sequence of community and ecosystem changes after a disturbance

A

Ecological succession

32
Q

Occurs where no soil exists when succession begins

A

Primary succession

33
Q

Begins in an area where soil remains after a disturbance

A

Secondary succession

34
Q

May facilitate the appearance of later species by making the environment more favorable

May inhibit establishment of later species

May tolerate later species but have no impact on their establishment

A

Early-arriving species

35
Q

Provide a valuable field-research opportunity on succession

A

Retreating glaciers

36
Q

Follows a predictable pattern of change in vegetation and soil characteristics

A

Succession on the moraines in Glacier Bay, Alaska

A. Pioneer stage, with fireweed dominant
B. Dryas stage
C. Spruce stage
D. Nitrogen fixation by Dryas and alder increases the soil nitrogen content.

37
Q

Biogeographic factors affect

A

community diversity

38
Q

Two key factors correlated with a community’s species diversity are

A

its geographic location and its size

39
Q

The two key factors in equatorial-polar gradients of species richness

A

Are probably evolutionary history and climate

40
Q

generally declines along an equatorial-polar gradient

And is especially great in the tropics

A

Species richness

41
Q

May account for the greater species richness

A

The greater age of tropical environments

42
Q

Is likely the primary cause of the latitudinal gradient in biodiversity

A

Climate

43
Q

The two main climatic factors correlated with biodiversity

A

Are solar energy input and water availability

44
Q

quantifies the idea that
all other factors being equal, the larger the geographic area of a community, the greater the number of species.

A ________ supports this idea

A

species-area curve;
species-area curve of North American breeding birds

45
Q

Habitat and Niche Key Concept:

A

Every organism has a habitat and a niche.

46
Q

differs from a niche.

is all aspects of the area in which an organism lives. (biotic factors and abiotic factors)

A

habitat

47
Q

includes all of the factors that a species needs to survive, stay healthy, and reproduce.
(food, abiotic conditions, behavior)

A

ecological niche

48
Q

Resource availability gives structure to a

A

community

49
Q

Species can share

A

habitats and resources

50
Q

occurs when two species use resources in the same way.

A

competition

51
Q

keeps two species from occupying the same niche.

A

Competitive exclusion

52
Q

different outcomes of competitive exclusion

A

One species is better suited to the niche and the other will either be pushed out or become extinct.
The niche will be divided.
The two species will further diverge.

53
Q

are species that occupy similar niches but live in different geographical regions.

A

Ecological equivalents

54
Q

is the variety of organisms that make up the community

A

Species diversity of a community

55
Q

two components of species diversity

A

species richness and relative abundance

(Two communities can have the same species richness but a different relative abundance )

56
Q

is the total number of different species in the community

A

Species richness

57
Q

is the proportion each species represents of the total individuals in the community

A

Relative abundance

58
Q

Diversity can be compared using a

A

diversity index

59
Q

H = – (pA ln pA + pB ln pB + pC ln pC + …)

where A, B, C . . . are the species, p is the relative abundance of each species, and ln is the natural logarithm

A

Shannon diversity index (H)

60
Q

Determining the number and abundance of species in a community is ____, especially for small organisms

A

difficult

61
Q

can be used to help determine microbial diversity

A

Molecular tools

62
Q

Ecologists manipulate diversity in experimental communities to study the _______.

For example, plant diversity has been manipulated at _______________.

A

potential benefits of diversity;

Cedar Creek Natural History Area in Minnesota for two decades

63
Q

Communities with higher diversity are

A

More productive and more stable in their productivity

Better able to withstand and recover from environmental stresses

More resistant to invasive specie

64
Q

organisms that become established outside their native range

A

invasive species

65
Q

Ecological Succession Key Concept:

A

Ecological succession is a process of change in the species that make up a community.

66
Q

occurs following a disturbance in an ecosystem.

regenerates or creates a community after a disturbance.
- a sequence of biotic changes
- damaged communities are regenerated
- new communities arise in previously uninhabited areas

A

Succession

67
Q

two types of succession.

A

primary succession
secondary succession

68
Q

started by pioneer species

A

primary succession

69
Q

started by remaining species

A

secondary succession

70
Q

or secondary natural succession

A

AUTOREGENERATION

71
Q

example of secondary natural succession of pioneer species on a land that was cleared from less than five years

A

Alim (Mallotus multiglandulosus),
Aratiles (Multingiacalabura),
Binunga (Macaranga tanarius),
Anabiong (Trema orientalis)

Hagonoy (Euphatorium odoratum)

Cogon grass

72
Q

Why does change or succession occur?

A

It occurs as the result of either autogenic processes (associated with the living community) or allogenic processes (associated with the physical environment).

73
Q

result of three major biotic mechanisms

A

Autogenic succession

74
Q

three major biotic mechanisms

A
  1. Colonization
  2. Alteration of the physical characteristics of the site
  3. Displacement of species by competition or antibiosis.

ECOLOGY (4 decks)

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