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Ecology and diversity > Lecture 19 and 20- community ecology > Flashcards

Lecture 19 and 20- community ecology Flashcards

1
Q

What is a community?

A

The species that live and interact in an area

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2
Q

What did detailed studies of plant distribution in Siskiyou mountains of oregon show?

A

Different combinations of plant species are found at different locations- species enter and drop out of communities independent over environmental gradients

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3
Q

What did Frederick Clements argue?

A

plant communities were tightly integrated “superorganisms.” Communities in similar areas would have the same species.

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4
Q

What did Henry Gleason argue?

A

plant communities are loose associations of species; each species was distributed based on its own
environmental requirements.

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5
Q

What can organisms be divided into based on the source of their energy?

A

Trophic levels

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6
Q

Autotrophic plants constitute a trophic level called…

A

(Photosynthesizers), primary producers

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7
Q

Heterotrophs that eat autotrophs are called…

A

herbivores or primary consumers

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8
Q

Organisms that eat herbivores are called…

A

Secondary consumers

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9
Q

Another type of trophic level is…

A

detritivores, decomposers.

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10
Q

Organisms that obtain food from more than one trophic level are called…

A

omnivores

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11
Q

A sequence of interactions in which a plant is eaten by a herbivore which in turn is eaten by a secondary consumer and so on can be diagrammed as a…

A

food chain

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12
Q

Food chains are interconnected to make…

A

a food web

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13
Q

Food webs help us to understand what?

A

The trophic interactions among organisms in an ecosystem

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14
Q

What are the 5 main ways that organisms interact with one another?

A
  • Predation or parasitism
  • Competition
  • Mutualism
  • Commensalism
  • Amensalism
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15
Q

What are commensalism interactions?

A

Interactions in which one participant benefits and the other in unaffected

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16
Q

What are amensalism interactions?

A

Interactions in which one participant is harmed and the other unaffected

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17
Q

What effect do these 5 types of interactions have?

A

Influence population densities of a species, restrict range of conditions under which animals exist.

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18
Q

What does mutualism do?

A

Increases the range of physical conditions under which a species can persist

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19
Q

How do predator and prey population change?

A

They oscillate

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20
Q

Why do predator and prey populations oscillate?

A

Predators cause fluctuations in prey densities, growth of predator population lags behind growth of prey populations.

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21
Q

Give an example of predator-prey interactions.

A

Arctic lemmings (prey) and predators: arctic fox, snowy owl, jaegers, 3-4 year oscillations

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22
Q

Give another example of predator-prey interactions.

A

Canadian lynx (Lynx canadensis) and snowshoe hares (Lepus americanus) with 9-11 year cycle

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23
Q

How was it proven that oscillations are driven by both lynx predation and interactions between hares and their food supply?

A

They enclosed some areas with fences through which hares but not lynx could pass, and provided food in some areas.

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24
Q

what do predators also restrict?

A

The range of a species

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25
Q

What is the Australasian biogeographic region home to?

A

A group of birds-megapodes, also called mound builders- who do not incubate their eggs.

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26
Q

How do megapodes keep their eggs warm?

A

By laying their eggs in a mound of decomposing vegetable material

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27
Q

Megapodes are good dispersers. Why are they absent from all islands with Asian mammalian predators?

A

Unattended eggs

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28
Q

What are the two types of mimicry?

A

Batesian mimicry

Mullerian mimicry

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29
Q

What is Batesian mimicry?

A

Palatable species mimic unpalatable or noxious species

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30
Q

What is Mullerian mimicry?

A

Two or more unpalatable or noxious species converge to resemble each other.

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31
Q

When does Batesian mimicry evolve?

A

Only if the mimic evolves towards unpalatable/noxious species faster then that species evolves away (mimic is less common than the unpalatable species)

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32
Q

What two consequences do interactions between species have?

A
  • Ecological consequences

- Evolutionary consequences

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33
Q

What do ecological consequences do?

A

Influence population densities

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34
Q

What do evolutionary consequences do?

A

Influence fitness of individual and lead to adaption.

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35
Q

What is reciprocal evolution between interaction species called?

A

Coevolution

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36
Q

What is a clear warning appearance of an individual called?

A

aposematism

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37
Q

What are the three classes in which members of the host population involved in microparasite-host interactions fall?

A

Susceptible
Infected
Recovered

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38
Q

What is the name of the bacterium that causes cholera?

A

Vibrio cholerae

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39
Q

How does cholera spread?

A

Ingestion of water containing V. cholerae

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40
Q

What does cholera bacterium do?

A

Toxin produced damages salt balance mechanisms

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41
Q

Why is competition widespread?

A

Because all species share resources

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42
Q

What are the two types of competition?

A
  • Interference competition

- Exploitation competition

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43
Q

What is interference competition?

A

Interfering with activities

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44
Q

What is exploitation competition?

A

Reducing available resources

45
Q

What are two types of competition between?

A

Intraspecific competition- among individuals of the same species
Interspecific competition- among individuals of different species

46
Q

What does intraspecific competition do?

A

Results in reduced growth and reproductive rates of some individuals, exclude some from habitats, cause death of some

47
Q

What does interspecific competition lead to if a superior competitor prevents all members of another species from using a habitat?

A

Competitive exclusion

48
Q

What two sessile animals compete for space in intertidal zones?

A

Two species of barnacles

  • Balanus balanoides
  • Chthamalus stellatus
49
Q

What is the distribution of the two species of barnacles?

A

Chthamalus live higher in the intertidal zone then Balanus with little overlap

50
Q

What happened when one of the species of the barnacle was removed?

A

Both increased vertical range when the other was removed.

51
Q

What was the conclusion of the barnacle experiment?

A

Chthamalus outcompete balanus in that zone- intertidal zonation is the result of competitive interaction.

52
Q

How can a species restrict the range of another species?

A

By reducing the populations of shared prey to such low levels the other species cannot persist

53
Q

What wasp was introduced to southern california?

A

Aphytis chrysomphali

54
Q

Why was Aphytis chrysomphali introduced to Southern California?

A

To control outbreak of scale insects damaging crops- did not work

55
Q

What wasp was introduced after Aphytis chrysomphali?

A

A.lingnanensis- higher reproductive rate, reduced population densities of Aphytis chrysomphali

56
Q

Give an example of amensalisms.

A

Herd of mammals drinking water at a water hole trample and kill many plants
Trees drop dead leaves and branches, harming plants and animals below

57
Q

Give an example of commensalisms.

A

Cattle egrets forage near mammals heads and feet to capture insects crushed by hooves and mouths.

58
Q

Give a mutualistic relationship involving rhinos

A

Oxpeckers pluck blood-sucking ticks from skin of grazing mammals

59
Q

Give an example of mutualistic relationships between fungi and plants.

A

Mycorrhizae

Nitrogen-fixing bacterium of genus Rhizobium

60
Q

Give an example of animals and protists in a mutalist relationship

A

Corals and other marine organisms gain energy from photosynthetic protists
Termites have cellulose digesting protists in their gut

61
Q

What are the two different niches that the barnacles could have occupied?

A

Fundamental niche- larger zone occupied when there is no competition
Realised niche- niche occupied when competitor is present.

62
Q

What is a trophic cascade?

A

Change in the relative population of different trophic levels in a food chain that follows the addition or removal of a trophic level

63
Q

Where can a trophic cascade be seen?

A

Wolf populations in the Lamar valley of yellowstone national park

64
Q

What do wolves feed on in Yellowstone?

A

Pronghorn, mule deer, elk, bison, bighorn sheep, moose

65
Q

When had wolves been extirpated from Yellowstone national park?

A

1926

66
Q

Elk were culled until 1968 to prevent…

A

Them from exceeding the parks carrying capacity

67
Q

What happened when wolves were absent with the elk?

A

They browsed aspen trees so intensely that no young trees grew after 1920
As well as stream side willow

68
Q

What was the result of elk eating too much stream side willow?

A

Beavers were nearly exterminated

69
Q

WHen were wolves reintroducted to yellowstone?

A

1995

70
Q

Where are adult dragonflies more abundant?

A

Around fish-free ponds

71
Q

What was less common around fish-free ponds?

A

Insect pollinators preyed on by dragonflies

72
Q

What happened when there were less insect pollinators near fish-free ponds?

A

St Johns wort was visited less commonly by pollinators, and therefore produced less seeds

73
Q

How do beavers cause trophic cascades?

A

Preferentially cutting down certain species of tree-alter vegetation composition
Building dams- creates meadows and ponds

74
Q

What are organisms that create structures called?

A

Ecosystem engineers

75
Q

What is a species that exerts an influence out of proportion to its abundance called?

A

A keystone species

76
Q

What is the latin name of the keystone species of starfish from the textbook?

A

Pisaster ochraceus- lives in rocky intertidal zone on Pacific coast

77
Q

What is the preferred prey of Pisaster orchraeceus?

A

Mussel Mytilus californianus

78
Q

How does P.ochraeceus act as a keystone species?

A

Stops M.californianus crowding the intertidal zone, creating spaces for other species.

79
Q

Give an example of a keystone species that isn’t a predator.

A

Fig tree species in tropical forests- fruit is ripe at times of year when food is scarce, fruit eating species depend on these figs.

80
Q

What is a disturbance?

A

An event that changes the survival rate of one or more species in an ecological community

81
Q

What happened in 1988 in yellowstone?

A

1/3 of the park was burnt in fires, created a mosaic of unburned patches, areas where herbs and shrubs were burned, areas were all trees were consumed.

82
Q

What is a change in the composition of an ecological community following a disturbance called?

A

Succession

83
Q

What are the two major types of succession?

A

Primary and secondary

84
Q

What is primary succession?

A

Begins on a site lacking organisms

85
Q

Where can primary succession be seen?

A

Changes in plant communities following the retreat of a glacier in glacier bay in Alaska over the last 200 years.

86
Q

What has the melting and retreat of the glacier left?

A

Moraines- gravel deposits

87
Q

What are the moraines closest to the glacial front populated with?

A

Bacteria, fungi, photosynthetic microorganisms

88
Q

What do slightly older moraines have?

A

Lichens, mosses, shallow rooted herbs.

89
Q

What is succession caused by?

A

In part by soil changes brought about by plants

90
Q

What plants grow best on the most recently formed moraines and why?

A

Herbaceous plants such as Dryas and Alnus with nitrogen fixing bacteria in root nodules. Spruce can then outcompete them.

91
Q

What can secondary succession begin with?

A

The dead parts of organisms- succession by fungal species

92
Q

Describe the decomposition of pine needles of Pinus sylvestris.

A

Fungi of several genera aid in successive decomposition of needles, degradation produces from one group of fungi are food for growth of next

93
Q

When is species richness greatest?

A

At intermediate levels of disturbance.

94
Q

What is the name given to the theory that species richness is greatest at intermediate levels of disturbance?

A

Intermediate disturbance hypothesis

95
Q

How does intermediate disturbance hypothesis work?

A
  • High disturbance: only species with greatest dispersal and reproduction persist
  • Low disturbance: competitively dominant species displace others.
96
Q

How was the intermediate disturbance hypothesis tested?

A

Using boulders in the intertidal zone on californian beaches.

97
Q

Why did medium sized boulders have more algae and barnacle species? How was the hypothesis tested?

A
  • Small boulders moved more often by waves

- Glued small boulders to substratum- after 6 months, these had more species

98
Q

What two things influence succession?

A

Facilitation and inhibition

99
Q

How did Wayne Sousa test if species inhibit colonization by other speices?

A

Removed all organisms from some boulders and placed them in the intertidal zone, removed species during succession, final successor took over faster

100
Q

What is species richness?

A

The number of species living in a community

101
Q

Are species more or less rich at higher latitudes?

A

Less

102
Q

Why are there more types of species in mountainous regions?

A

Because there are more vegetation types and climates.

103
Q

Why are there less species richness on islands and peninsulas?

A

Differences in immigration and extinction rates

104
Q

Species richness _______ with increasing productivity.

A

Increases

105
Q

Why does species richness increase with productivity?

A

Number of individuals an area can support increases, larger populations, less extinction.

106
Q

Why does species richness decrease when productivity surpasses a further point?

A

Interspecific competition become more intense, resulting in competitive exclusion

107
Q

Why does species richness enhance productivity?

A

A richer mixture of species results in more complete resource usage
Changing environment- more likely to have a species adapted to new conditions- therefore more stable

108
Q

How was the hypothesis that communities with many species should have higher productivity and stability than communities with few species tested?

A

Clear and plant pots with different numbers and mixtures of grass species. measure productivity and species composition of plots over 11 years.

109
Q

What was the result of the plant pot experiment?

A

Productivity increases with species richness

Variation in productivity decreases with species richness

Ecology and diversity (17 decks)

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