Final Exam - Community Ecology - Lecture 14 - Fill in the Blanks

Question 1

Food chain length depends on the amount of ________ _________ ________ (_).

Answer 1

Potential primary productivity or G

Question 2

What are the names of the four major hypotheses on why food chain lengths differ?

Answer 2

1 - Energy limitation hypothesis
2 - Dynamic stability hypothesis
3 - Ecosystem size hypothesis
4 - Productive space hypothesis

Question 3

_____ _______ hypothesis: longer food chains are less resilient so disturbance frequency/intensity limit food chain length.

Answer 3

Dynamic stability

Question 4

________ ______ hypothesis: large ecosystems support more individuals and more species.

Answer 4

Ecosystem size

Question 5

______ _______ hypothesis: food webs are inefficient; more productive environments support longer food chains.

Answer 5

Energy limitation

Question 6

_______ ______ hypothesis: ecosystem size and productivity act together.

Answer 6

Productive space

Question 7

To determine which factor affected food chain lengths in lakes, researchers performed treatments that included:
1 - ___________ alone
2 - __________ alone
3 - Combination of 1 and 2
(note that the lines may represent more than one word)

Answer 7

1 - Productivity

2 - Ecosystem size

Question 8

Problems in testing food chain lengths hypotheses has been the inability to measure _____ _____ _____ and _________ _____.

Answer 8

Food chain length and ecosystem size

Question 9

Post et al., used ______ _______ techniques to determine food chain length (maximum trophic position)

Answer 9

stable isotope

Question 10

In stable isotope analysis, Carbon changes little through the food web, but is used to determine sources of _______.

Answer 10

energy

Question 11

Productivity for small, medium and large lakes:

Maximum trophic position did ___ __________ with increased productivity

Answer 11

not increase

Question 12

The conclusions of the Post et al (Stable isotope), study was that:
1 - Found ________ _____ was the ONLY factor that determined food chain length
2 - suggests that factors related to food chain length are not resolved
3 - At present, ________ _____ followed by ________ hypothesis are main factors

Answer 12

1 - ecosystem size

3 - Ecosystem size; productivity

Question 13

Charles Elton on Food Chains vs. Food Webs:
- Food chains were “limited to _____ or _____ ______”
- Several food chains occur linked together as a food web
Chains and webs used to illustrate __________ in _________: (such as predator prey, host/parasitoid and mutualistic relationships)

Answer 13

1 - four or five links

2 - interactions in communities

Question 14

Nodes (S) (definition)

Answer 14

the organisms that occur in the food web

Question 15

Links (L): generally given as arrows to show the direction/strength of the _________ or ___________.

Answer 15

Interaction or relationship

Question 16

Linkage density is given by the equation: /.

Answer 16

L/S
where,
L is the number of links and S is the number of nodes

Question 17

What is connectance?

Answer 17

Number of observed links in the network.

given as a proportion of observed links to total possible links

Question 18

Increased connectance promotes _________ in the food web.

Answer 18

Stability

Question 19

Chain length: the number of _____ ______ in the chain or web.

Answer 19

Trophic levels

Question 20

Source webs: all species in the web arise from the ______ _______ _______.

Answer 20

Same source species

Question 21

Sink webs: where feeding relationships lead to a _____ ____ ________.

Answer 21

Single top predator

Question 22

Community web (definition)

Answer 22

The entire set of feeding relations possible in a community (never fully realized)

Question 23

Connectedness web:

• illustrate _______ ________
• trophic links are given as arrows pointing to the consumer
• No indication of ________ _________

Answer 23

1) Feeding relationships

2) Interaction strengths

Question 24

Green food webs:

• Food webs with ______ _______ at the base
• _____ energy channels

Answer 24

1) Primary producers

2) fast

Question 25

Brown food webs:

• Food webs with ________ at the base
• ____ energy channels

Answer 25

1) Detritus

2) Slow

Question 26

Energy flow webs:

• illustrate the pattern of _____ _____ through the community
• Difficult to build - it is hard to get such difficult information
• _______ ____ is not a good indicator of _________ _______ between species at different trophic levels
• Considers Lotka’s _________ concept of the ecosystem and Odum’s depiction of the ecosystem as a _____ diagram

Answer 26

1) Energy flow
2) Energy flow; Interaction strength
3) thermodynamics; flow

Question 27

Food webs are \_\_\_\_\_\_.
Energy is lost via:
1) \_\_\_\_\_\_ energy - used to produce indigestible structures
2) \_\_\_\_\_\_ energy - lost as heat
3) \_\_\_\_\_\_\_ energy - nitrogenous wastes

Answer 27

• inefficient
  1) Egested
  2) Respired
  3) Excreted

Question 28

_________ energy = ingested - egested energy

Answer 28

Assimilated

Question 29

_________ = assimilated - respired - excreted energy

Answer 29

Production

Question 30

Energy available at each level of the food web depends on the ___ ________ ________ at the base of the web and _________ ________ between trophic levels

Answer 30

1) Net primary production

2) Transfer efficiency

Question 31

Plants use 15-70% of the energy they absorb for maintenance = maximum 30-85% for assimilation by herbivores
BUT, energy transfer is ______. Only _-__% of energy available at one level is ________ to the next

Answer 31

Energy transfer is inefficient. Only 5-20% of the energy available at one level is assimilated by the next.

Question 32

What is net production efficiency?

Answer 32

The ratio of energy contained in production to total assimilated energy (= production/assimilated energy)

Question 33

Net production efficiency is ____ for active, warm blooded animals and ____ for sedentary, cold-blooded animals.

Answer 33

1) High

2) Low

Question 34

What is the equation for assimilation efficiency?

Answer 34

Assimilation efficiency = assimilation/ingestion

Question 35

According to Raymond Lindemand, assimilation efficiency is the fraction of energy entering one trophic level that is ______ onto the _____ _____ _____.
Transfer is ________. And this is why food chains are _____.

Answer 35

1) passed onto the next higher level.
2) Inefficient
3) Short

Question 36

Functional webs:

1) illustrate the _______ of populations of each species in the web on the ______ ______ in the web
2) Size of the arrow represents the ________ of the __________
3) Communities include _____ and _____, _____ and _______ interactions.
4) Not all interactions are _______ _________

Answer 36

1) impact; other species
2) strength of the interaction
3) weak and strong; direct and indirect
4) equally important

Question 37

How does one determine interaction strength?

• Experimental manipulation:
  1) Remove ______ from the _________ and observe what happens to the other _______

Answer 37

1) Species; community; species

Question 38

Indices of interaction strength:
N = ____ [normal condition] (sentence answer)
D = ______ [Deleted predator]
Y = abundance of _______
Py = proportional abundance of the ________
t = time

Answer 38

N = abundances of prey when predators are present
D = number of prey without predators
Y = abundance of predators
Py = proportional abundance of the predator

Question 39

Paine’s index = (N-D)/DY

• Quantifies the effect of the ______ or _______ on the ________ _______ in the community
• The dominant resource has the potential to form a _________ in the ________ of the consumer

Answer 39

1) predator or consumer; dominant resource

2) monoculture; absence

Question 40

Community importance = ((N-D)/NPy))

• Quantifies the effect of a ______ relative to its ________
• Distinguishes ________ from dominant species in the community

Answer 40

1) species; abundance

2) Keystone

Question 41

Dynamic index = ln(N-D)/Yt

- Compares the log ratio of _____ abundance when predators are _______ to when predators are ________

Answer 41

1) Prey abundance when predators are present to when predators are absent

Question 42

What about observational data? (Bascompote et al.)
IS = [(Q/B)j x DCij]/Bi
Where,
IS = \_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_
Bi = \_\_\_\_\_ of the \_\_\_\_\_\_

Answer 42

IS = interaction strength
Bi = biomass of the prey

Question 43

Functional food webs:

• research has show that, for multiple food webs that:
• most food webs contain a ____ ______ and many ______ links

Answer 43

few strong and many weak links

Question 44

Food web stability:

- simple communities were more prone to _______ _______ and fluctuations in ______ ________

Answer 44

Simple communities are more prone to (species invasions) and fluctuations in (species abundance)

Question 45

Simple communities are ________ communities.

Complexity adds ________ to communities.

Answer 45

1) Unstable

2) Stability

Question 46

Robert May:

Modeled ecosystems by randomly assigning interaction strengths and showed that complex communities were _____ ______.

Answer 46

Less stable

Question 47

McCann et al: weak interactions in complex communities dampen population oscillations = _______ _______

Answer 47

increased stability

Question 48

Ricklefs: an omnivore is an organism with a broad diet, including both plant and animal foods; an omnivore feeds from _______ _______ ______.

Answer 48

Multiple trophic levels

Question 49

Based on theoretic models, Pimm and Lawton predicted that it should be _____ __ ____ species that feed simultaneously both high and low in the food web.

Answer 49

Rare to find

Question 50

Because omnivores can alter their diet, their populations tend to be _____ _____ due to the _______ effect.

Answer 50

More stable = refuge effect

Question 51

Singer and Bernays: Due to switching behaviour, omnivores interact _______ with their food sources
- weak interactions –> _____ food webs

Answer 51

1) Weakly

2) Stable

Question 52

Lafferty et al., estimate that 75% of links in food webs involve parasites:
- including parasites _______ food chain _____ and _______

Answer 52

(Increases) food chain (length) and (stability)

Question 53

If parasites stabilize food webs, why are they not included?
1 - Small in size (hard to identify and quantify)
2 - Complex life cycles
3 - May have multiple hosts at different _____ _____
4 - Energy transfer is _____ to measure because _______ do not _____ their hosts
5 - Parasites affect host behaviour, altering ______ ________

Answer 53

3) trophic levels
4) hard; parasites; kill
5) interaction strengths