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Exam (elaborations)

Bio 250 Final Exam Questions and Correct Answers

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  • Module
  • BIO 250
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  • BIO 250

What is community ecology? the study of interactions between species and how they influence community structure and function Ecologists define a community as: species within a particular place that interact or potentially interact Disturbance: A discrete event that disrupts an ecosystem or commun...

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  • September 3, 2024
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  • BIO 250
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Bio 250 Final Exam Questions and
Correct Answers
What is community ecology? ✅the study of interactions between species and how they
influence community structure and function

Ecologists define a community as: ✅species within a particular place that interact or
potentially interact

Disturbance: ✅A discrete event that disrupts an ecosystem or community

Succession: ✅the repeatable change in community composition through time following
a disturbance

Succession is affected by: ✅self thinning, life history traits

Primary succession: ✅initial establishment of a community

Secondary succession: ✅re-establishment of existing community

What are the 3 models of succession? ✅facilitation, tolerance, inhibition

What is facilitation? ✅When one species opens up niches for other species to grow,
stress-tolerant species make it more habitable

What is inhibition? ✅whoever gets there first survives, inhibits growth of other colonies

What is tolerance? ✅whoever gets there first survives, but has no effect on other
species

What is a climax community? ✅succession progresses towards this, seen as a stable
endpoint

What are allogenic processes? ✅outside influences that effect communities such as
human interventions, immigration by new species, seasonal changes, abiotic
disturbances

What is an example of an allogenic process? ✅human interventions, immigration by
new species, seasonal changes, abiotic disturbances

What do allogenic processes ensure? ✅That a community is almost never in
equilibrium

,Intermediate disturbance hypothesis: ✅species diversity will be greatest when
disturbances are of intermediate frequency, when an intermediate amount of time has
passed after a disturbance, or when the disturbance is of intermediate magnitude

Most species live at ___ amounts of disturbance. ✅intermediate

Direct benefit: ✅from the source to the other thing

Indirect benefit: ✅from the source to another thing and then the other thing

Where does the flow of energy begin? and with who? ✅the first trophic level, primary
producers

What occupies the second trophic level? ✅herbivores

What occupies the third trophic level? ✅predators

What occupies the fourth trophic level? ✅animals that feed directly on predators

Primary consumers only get about ___ of the energy of the producers. ✅10%

What is top-down control? ✅higher trophic level limits the size of the trophic level they
consume

Predation limits ___ and releases pressure on ___. ✅herbivores, vegetation

When a predator is removed, number of herbivores ___ and vegetation ___.
✅increases, decreases

what is a behavioral cascade? ✅where a predator indirectly stimulates primary
production by altering the foraging behavior of its prey

autogenic engineer (indirect): ✅result from the internal architecture of the engineer
itself (corals, trees)

allogenic engineers (indirect): ✅result from the redistribution of living or non-living
materials (beaver dams)

Bottom-up hypothesis: ✅organisms at each trophic level are resource-limited; food-
chain length increases as resource-availability increases

What is an example of the bottom-up hypothesis? ✅crop production increases when
fertilizer (nutrients) are applied

, Even when production is high ___ may limit higher trophic levels because many plants
are low quality food. ✅bottom up control

Productivity hypothesis: ✅more productive ecosystems should have longer food
chains
ex) lakes with higher P concentrations would have longer food chains but that lake size
wouldn't matter

ecosystem size hypothesis: ✅food chain length should increase with ecosystem size
ex) larger lakes would have longer food chains but that P concentration wouldn't matter

productive space hypothesis: ✅food chain length would increase with both phosphorus
concentration and lake size
ex) food chain length would increase with both phosphorus concentration and lake size

Top-down control ✅Energy flow is governed by rates of consumption at the higher
trophic levels which influence abundance at lower trophic levels (Food chain length
determines whether or not herbivores limit plants)

bottom-up control ✅Organisms at each trophic level are resource-limited
(Food-chain length increases as resource-availability increases)

Resistance: ✅ability to withstand a disturbance

Return time: ✅the time required to return to equilibrium after disturbance
(depends on type of disturbance)

Resilience: ✅how closely does the post-recovery community resemble the pre-
disturbance community

High resilience = ✅same species and proportions before/after disturbance

Low resilience = ✅species composition amd relative abundance change after
disturbance

When do alternative stable states occur? ✅occur when more than one type of
community can exist in a particular environment

what is an alternative stable state? ✅a low resilience community may transition into a
very different equilibrium state after a disturbance

Connectance (C) food web formula: ✅links / species ^2

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