Final Exam - Community Ecology - Lecture 13 - Fill in the Blanks Flashcards Preview

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Flashcards in Final Exam - Community Ecology - Lecture 13 - Fill in the Blanks Deck (40):

What are indirect effects?

When one species affects a second species through a change in an intermediate 3rd species.


What are examples of indirect effects?

Indirect mutualism, apparent competition, habitat facilitation, trophic cascades, etc.


What are keystone species?

Species whose effects on the ecosystem are disproportionately large for their biomass.


Exploitative competition is an example of what?

Indirect effects


Interference competition is an example of what?

Direct effect


What is exploitative competition?

Also called resource competition.
Occurs when species share a limited resource, making the resource less available for the other species.


What is interference competition?

Occurs when one species limits access of another species to a limiting resource.


What is apparent competition?

Non-competing species that share a predator may have negative indirect effects on each other by increasing predation on each other.


What is facilitation?

An interaction where presence of one species alters the environment to enhance growth, survival and reproduction of another species.


What is habitat facilitation?

Foundation species modify habitat to provide structure habitat for other species.


Size-selective predation affects the _______ of ______ as well as ______ species. (in freshwater planktonic communities)

1) diversity
2) predator
3) prey


Dodson's hypothesis was: complementary feeding niches by size selective predation.
In his study he found that:
Larval salamander creates a feeding niche for a second predator via _____ ______ _______ on _____ zooplankton.

1) size selective feeding
2) large


Tested Dodson's hypothesis by ______ _______ ____ from 1 arctic pond and compared to a control pond.

Removing salamander eggs


The interaction between the salamander and the small zooplankton is what?



Removal of ______ shifts zooplankton to _____ sized species and this corresponds to a decline in Chaoborus, the _____ sized species.

1) Salamander
2) Large
3) Small


Trophic cascades:
- Effect of one species is:
- _______ to the trophic level below it
- _______ to the next lowest level
- ________ to the next lowest level after that
- continuing in an ________ _______ depending on the number of trophic levels in the food web

1) Negative
2) positive
3) Negative
4) Alternating effect


Trophic cascades are referred to as ___-___ processes.



There are six reasons to why the world is green, the first three are:
1 - Not all that is green is ______
2 - Nutrients critical for animals are often in _____ _____ in ______ matter so ________ can't obtain sufficient nutrients to grow and reproduce
3 - ______ factors limit herbivores

1 - edible
2 - short supply in plant matter so herbivores
3 - abiotic factors


There are six reasons to why the world is green, the last three reasons are:
4 - _______ and ________ __________ reduce availability of herbivores can't always locate plants efficiently
5 - Herbivores limit their own numbers via __________ and ___________ _________
6 - ________ limit herbivores

4 - spatial and temporal heterogeneity reduce the availability of plants
5 - intraspecific and interference competition
6 - predators


Which of the six reasons why the world is green is the hallmark of the World is Green hypothesis?

Number six: predators limit herbivores.


The HSS (or the World is Green) model has a couple different key notions:
- ________ reduce the abundance of ________ which increase ________
- 3 trophic levels
- herbivores are _______ limited
- terrestrial food chains

1) Predators reduce the abundance of herbivores which increase producers
2) herbivores are predator limited


Another insight from the HSS model is that:
- one process, either _______ ________ or _______ ________, should dominate at any given trophic level.

Resource limitation or predator limitation


There are also criticisms to the HSS model:
1 - Plants have _________, reducing the effects of _________ on plants
2 - _________ may be limited by territories/nesting sites (factors from the previous six reasons)
3 - Applicable to food chains but, most communities have _____ _____

1) defenses; herbivores
2) Herbivores
3) food webs


The HSS paper initiated what was to become the _______ ________.

trophic cascade


How did Okanen (or Oksanen) test HSS?

Treated each trophic level as a single homogeneous population.


What is potential primary productivity (G)?

the maximum primary productivity allowed by the environment in the absence of consumers.


What was Oksanen's hypothesis?

Ecosystems with low G support fewer trophic levels (smaller chain)


Oksanen found that herbivore population (consumer density) is limited by what?

Both resource limitation and predators


Craig Osenberg and Gary Mittelbach - data from an oligotrophic lake
- Each trophic level showed a greater change in ________ in response to resource addition than predator removal.
- so, ________ ________ was more severe than _________ _________ for each trophic level

1) biomass
2) resource limitation; predator limitation


There are three predictions of the consumer-resource theory applied to trophic levels:
1 - In food chains of a given length, an increase in G will increase abundances of populations at ___ trophic levels and _________ trophic levels, but not _________ trophic levels
2 - Reduction in abundances of populations at top trophic levels will alternatively increase and decrease abundances in lower trophic levels - a ______ ______
3 - Increase in G should increase ________ of ________ _________ in an ecosystem (increase food chain ______)

1) top; alternating; intervening
2) trophic cascade
3) number of trophic levels; food chain


Other studies of natural studies have demonstrated abundances of ____ trophic levels increased with __.
This means that ______ _______ within the food web matters.

1) all
2) G
3) species composition


Wooton and Power;
Manipulated ________ levels primary productivity in a California river: replicates of various _______ (_______ = photosynthesis) treatments over _________

1 - light
2- shade
3 - light
4 - channels


In the example of a food web where herbivores represent 2 prey types that share a common resource and predator;
Herbivore 1 (N1) is a better _________ __________ but is more vulnerable to ________; N2 on the other hand is more __________ resistant

1 - resource competitor
2 - predation
3 - predator


Heterogeneity in species composition with trophic level, together with trade-off between competitive ability and vulnerability to predation leads to:
1) ________ ___________ along productivity gradients
2) _________ in _________ of all trophic levels with increase in G

1) Species replacements
2) Increases in abundance


A species replacement along a productivity gradient represents a shift from a good _______ _______ to good ________ __________.

Resource competitor to predator resistor


What are three examples of potential mechanisms by which resources are less available to higher trophic levels?

-Adaptive foraging behaviours
-Inducible defences
-ratio-dependent predation
-complex life histories (invulnerable life stages)


Resource limitation and predator limitation should often act in concert to limit __________.
But, not simply a dichotomy of top-down vs. bottom up.
_______ ________ may differ.

1) abundance
2) Relative strengths


Predation limiting herbivores would be an example of ___-___ control whilst resource limitation would be an example of ___-___ control.

- Top-down
- Bottom-up


There are many reasons for why trophic cascades are more prevalent in aquatic ecosystem rather than terrestrial ones. These include:
1 - Terrestrial producers are _____(sentence)
2 - Terrestrial food webs have more _______ (sentence)
3 - Relative sizes of producers and consumers and nutritional quality of plants compared to algae

1 - Terrrestrial producers are longer lived and better defended against herbivory
2 - Terrestrial food webs have more generalists feeder, more omnivores and so more diverse pathways and weaker interaction strengths due to multiple food web links


Trophic cascades provide strong evidence for importance of ___-___ processes; yet, says little about the relative importance of _______ vs. _________ limitation.

1 - Top-down
2 - resource vs. predator limitation