Final Exam - Community Ecology - Lecture 14 - Fill in the Blanks Flashcards
Food chain length depends on the amount of ________ _________ ________ (_).
Potential primary productivity or G
What are the names of the four major hypotheses on why food chain lengths differ?
1 - Energy limitation hypothesis
2 - Dynamic stability hypothesis
3 - Ecosystem size hypothesis
4 - Productive space hypothesis
_____ _______ hypothesis: longer food chains are less resilient so disturbance frequency/intensity limit food chain length.
Dynamic stability
________ ______ hypothesis: large ecosystems support more individuals and more species.
Ecosystem size
______ _______ hypothesis: food webs are inefficient; more productive environments support longer food chains.
Energy limitation
_______ ______ hypothesis: ecosystem size and productivity act together.
Productive space
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)
1 - Productivity
2 - Ecosystem size
Problems in testing food chain lengths hypotheses has been the inability to measure _____ _____ _____ and _________ _____.
Food chain length and ecosystem size
Post et al., used ______ _______ techniques to determine food chain length (maximum trophic position)
stable isotope
In stable isotope analysis, Carbon changes little through the food web, but is used to determine sources of _______.
energy
Productivity for small, medium and large lakes:
Maximum trophic position did ___ __________ with increased productivity
not increase
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
1 - ecosystem size
3 - Ecosystem size; productivity
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)
1 - four or five links
2 - interactions in communities
Nodes (S) (definition)
the organisms that occur in the food web
Links (L): generally given as arrows to show the direction/strength of the _________ or ___________.
Interaction or relationship
Linkage density is given by the equation: /.
L/S
where,
L is the number of links and S is the number of nodes
What is connectance?
Number of observed links in the network.
given as a proportion of observed links to total possible links
Increased connectance promotes _________ in the food web.
Stability
Chain length: the number of _____ ______ in the chain or web.
Trophic levels
Source webs: all species in the web arise from the ______ _______ _______.
Same source species
Sink webs: where feeding relationships lead to a _____ ____ ________.
Single top predator
Community web (definition)
The entire set of feeding relations possible in a community (never fully realized)
Connectedness web:
- illustrate _______ ________
- trophic links are given as arrows pointing to the consumer
- No indication of ________ _________
1) Feeding relationships
2) Interaction strengths
Green food webs:
- Food webs with ______ _______ at the base
- _____ energy channels
1) Primary producers
2) fast
Brown food webs:
- Food webs with ________ at the base
- ____ energy channels
1) Detritus
2) Slow
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
1) Energy flow
2) Energy flow; Interaction strength
3) thermodynamics; flow
Food webs are \_\_\_\_\_\_. Energy is lost via: 1) \_\_\_\_\_\_ energy - used to produce indigestible structures 2) \_\_\_\_\_\_ energy - lost as heat 3) \_\_\_\_\_\_\_ energy - nitrogenous wastes
- inefficient
1) Egested
2) Respired
3) Excreted
_________ energy = ingested - egested energy
Assimilated
_________ = assimilated - respired - excreted energy
Production
Energy available at each level of the food web depends on the ___ ________ ________ at the base of the web and _________ ________ between trophic levels
1) Net primary production
2) Transfer efficiency
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
Energy transfer is inefficient. Only 5-20% of the energy available at one level is assimilated by the next.
What is net production efficiency?
The ratio of energy contained in production to total assimilated energy (= production/assimilated energy)
Net production efficiency is ____ for active, warm blooded animals and ____ for sedentary, cold-blooded animals.
1) High
2) Low
What is the equation for assimilation efficiency?
Assimilation efficiency = assimilation/ingestion
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 _____.
1) passed onto the next higher level.
2) Inefficient
3) Short
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 _______ _________
1) impact; other species
2) strength of the interaction
3) weak and strong; direct and indirect
4) equally important
How does one determine interaction strength?
- Experimental manipulation:
1) Remove ______ from the _________ and observe what happens to the other _______
1) Species; community; species
Indices of interaction strength:
N = ____ [normal condition] (sentence answer)
D = ______ [Deleted predator]
Y = abundance of _______
Py = proportional abundance of the ________
t = time
N = abundances of prey when predators are present D = number of prey without predators Y = abundance of predators Py = proportional abundance of the predator
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
1) predator or consumer; dominant resource
2) monoculture; absence
Community importance = ((N-D)/NPy))
- Quantifies the effect of a ______ relative to its ________
- Distinguishes ________ from dominant species in the community
1) species; abundance
2) Keystone
Dynamic index = ln(N-D)/Yt
- Compares the log ratio of _____ abundance when predators are _______ to when predators are ________
1) Prey abundance when predators are present to when predators are absent
What about observational data? (Bascompote et al.) IS = [(Q/B)j x DCij]/Bi Where, IS = \_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_ Bi = \_\_\_\_\_ of the \_\_\_\_\_\_
IS = interaction strength Bi = biomass of the prey
Functional food webs:
- research has show that, for multiple food webs that:
- most food webs contain a ____ ______ and many ______ links
few strong and many weak links
Food web stability:
- simple communities were more prone to _______ _______ and fluctuations in ______ ________
Simple communities are more prone to (species invasions) and fluctuations in (species abundance)
Simple communities are ________ communities.
Complexity adds ________ to communities.
1) Unstable
2) Stability
Robert May:
Modeled ecosystems by randomly assigning interaction strengths and showed that complex communities were _____ ______.
Less stable
McCann et al: weak interactions in complex communities dampen population oscillations = _______ _______
increased stability
Ricklefs: an omnivore is an organism with a broad diet, including both plant and animal foods; an omnivore feeds from _______ _______ ______.
Multiple trophic levels
Based on theoretic models, Pimm and Lawton predicted that it should be _____ __ ____ species that feed simultaneously both high and low in the food web.
Rare to find
Because omnivores can alter their diet, their populations tend to be _____ _____ due to the _______ effect.
More stable = refuge effect
Singer and Bernays: Due to switching behaviour, omnivores interact _______ with their food sources
- weak interactions –> _____ food webs
1) Weakly
2) Stable
Lafferty et al., estimate that 75% of links in food webs involve parasites:
- including parasites _______ food chain _____ and _______
(Increases) food chain (length) and (stability)
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 ______ ________
3) trophic levels
4) hard; parasites; kill
5) interaction strengths
