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ECOLOGY LECT > Community Ecology > Flashcards

Community Ecology Flashcards

1
Q

Key points of Community Ecology

A

A community’s structure can be described by its species richness, and species diversity

Community structure is influenced by many factors, including abiotic factors, species interactions, level of disturbance, and chance events.

Some species, such as foundation species and keystone species, play particularly important roles in determining their communities structure.

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2
Q

Number of species present

A

Species richness

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3
Q

A measure of both species richness and species evenness (relative numbers)

A

Species diversity

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4
Q

Is the feeding relationships between organisms in a community.

A key factor in community dynamics.

A

Trophic structure

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5
Q

Link trophic levels from producers to top carnivores

A

Food chains

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6
Q

Terrestrial food chain (5)

A

Plant - Primary producers

Herbivore - Primary consumers

Carnivore - Secondary consumers

Carnivore - Tertiary consumers

Carnivore - Quarternary consumers

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7
Q

Marine food chain

A

Phytoplankton - Primary producers

Zooplankton - Primary consumers

Carnivore - Secondary consumers

Carnivore - Tertiary consumers

Carnivore - Quarternary consumers

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8
Q

A branching food chain with complex trophic interactions

A

Food web

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9
Q

T or F: Species may play a role at MORE than ONE trophic level

A

True

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10
Q

Food webs can be simplified by (2)

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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11
Q

T or F: Each food chain in a food web is multiple links long

A

False, a food web is usually only a FEW links long

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12
Q

Hypotheses attempting to explain food chain length (2)

A

Energetic hypothesis

Dynamic stability hypothesis

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13
Q

Suggests that length is limited by inefficient energy transfer

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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14
Q

Proposes that long food chains are less stable than short ones

A

Dynamic stability hypothesis

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15
Q

The total mass of all individuals in a population

A

biomass

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16
Q

T or F: most data support the dynamic stability hypothesis

A

False, most data support the energetic hypothesis

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17
Q

Are those that are most abundant or have the highest biomass

Exert powerful control over the occurence and distribution of other species

A

Dominant species

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18
Q

Example of Dominant Species (1)

A

Sugar maples
- have a major impact on shading and soil nutrient availability in eastern North America; affects the distribution of other plant species

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19
Q

Two hypotheses on dominant species (2)

A

-Suggests that dominant species are most competitive in exploiting resources

-Suggest that they are most successful at avoiding predators

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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

T or F: Like dominant species, it is necessary for a keystone species to be abundant in a community

A

False, they are not necessarily abundant in a community

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23
Q

A Keystone species in intertidal communities (1)

A

Sea stars

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24
Q

An event that changes a community

Removes organisms from a community

Alters resource availability

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

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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

Large-scale fire in yellowstone national park in 1988

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28
Q

Prairie fire progression (3)

A

a) BEFORE A CONTROLLED BURN
a prairie that has not burned for several years has a high proportion of DETRITUS (dead grass)

b)DURING THE BURN
detritus serves as fuel for the fires

c) AFTER THE BURN
approximately one month after the controlled burn, virtually all of the biomass in the prairie is living

29
Q

Large-scale fire in Yellowstone National Park progression (2)

A

a) SOON AFTER FIRE
the burn left a patchy landscape

b) ONE YEAR AFTER FIRE
A variety of herbaceous plants, different from those in the former forest, cover the ground.

30
Q

Are the most widespread agents of disturbance

A

Humans

31
Q

Humans disturbance to communities : ___

Humans also prevent some naturally occuring disturbances : ___

A

Usually reduces species diversity

Which can be important to community structure

32
Q

Is the sequence of community and ecosystem changes after a disturbance

A

Ecological succession

33
Q

Types of ecological succession (2)

A

Primary succession
– Occurs where no soil exists when succession begins

Secondary succession
– Begins in an area where soil remains after a disturbance

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

37
Q

Succession on the moraines in Glacier Bay, Alaska (4)

A

a) pioneer stage, with firewood dominant

b) Dryas stage

c) Spruce stage

d) Nitrogen fixation by Dryas and alder increases the soil nitrogen content

38
Q

Two key factors correlated with a community’s species diversity

A

Geographic loaction and its size

39
Q

Two key factors in equatorial-polar
gradients of species richness

A

Evolutionary history
Climate

40
Q

Species richness generally declines along an
___ and is especially great in the tropics

A

equatorial-polar gradient

41
Q

May account for the greater species richness of tropical environments

A

The greater age of tropical environments

42
Q

Is likely the primary cause of the latitudinal gradient in biodiversity

A

Climate

43
Q

two main climatic factors correlated with biodiversity

A

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

species-area curve

-supported by the species-curve of North American birds

45
Q

Every organism has a ___ and a ___.

A

Habitat, Niche

46
Q

A ___ is all aspects of the area in which an organism lives.

A

habitat

47
Q

An ___ includes all of the factors that a species needs to survive, stay healthy, and reproduce.

A

ecological niche

48
Q

Under habitat (2)

A

biotic factors
abiotic factors

49
Q

Under ecological niche (2)

A

-food
– abiotic conditions
– behavior

50
Q

___ gives structure to a
community.

A

Resource availability

51
Q

occurs when two species use resources in the same way.

A

competition

52
Q

keeps two species from occupying the same niche.

A

Competitive exclusion

53
Q

Competitive exclusion has different outcomes (3)

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.

54
Q

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

A

Ecological equivalents

55
Q

is the variety of organisms that make up the community

A

Species diversity

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

T or F: Two communities can have the same species richness but a different relative abundance

A

True

59
Q

Diversity can be compared using a ___

A

diversity index

(Shannon diversity index (H))

60
Q

Shannon diversity index (H)

A

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

61
Q

can be used to help determine microbial diversity

A

Molecular tools

62
Q

T or F: Ecologists abstain from manipulating diversity in experimental communities to study the potential benefits of diversity

A

False: Ecologists manipulate diversity in experimental
communities to study the potential benefits of diversity

63
Q

Example of Ecologists manipulating diversity

A

For example, plant diversity has been manipulated at Cedar Creek Natural History Area in Minnesota for two decades

64
Q

Communities with higher diversity are (3)

A
  • More productive and more stable in their productivity
  • Better able to withstand and recover from environmental stresses
  • More resistant to invasive species, organisms that become established outside their native range
65
Q

Succession regenerates or creates a community after a disturbance (3)

A
  • a sequence of biotic changes
  • damaged communities are regenerated
  • new communities arise in previously uninhabited areas
66
Q

Why does change or succession occur? (2)

A

autogenic processes (associated with the
living community)

allogenic processes
(associated with the physical environment)

67
Q

Different name for secondary natural succession

A

AUTOREGENERATION

68
Q

Autogenic succession - result of 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 LECT (12 decks)

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