EEB 3407 Exam 1 Questions with Correct
Answers
Define community.
A community is a group of individuals of different species occupying a particular place at a
particular time.
Compare resources and conditions.
Resources are used up by organisms and their availability changes with the number of
organisms, such as food or nutrients. Conditions affect organisms but are not consumed, such
as temperature or pH.
Define niche.
A niche is the range of biotic and abiotic tolerances and requirements that allow a species to
survive and reproduce.
Compare fundamental and realized niche.
The fundamental niche is where a species could survive and reproduce without interspecific
interactions. The realized niche is where it actually survives and reproduces in the presence
of interspecific interactions.
What does R* represent?
R is the minimum amount of a resource needed to sustain a species. A species with a
lower R is usually the better competitor for that limiting resource.
Explain the most likely outcome of competition for one limiting resource.
In a homogeneous environment with one limiting resource, the species with the lowest R* is
expected to win because it can reduce the resource below the level needed by competitors.
, What is a ZNGI?
A zero net growth isocline is a line showing combinations of species densities or resources
where the population growth rate is zero.
What does stable coexistence mean in competition?
Stable coexistence occurs when both species can invade from low abundance and persist
together. If one species becomes rare, it can increase, helping maintain coexistence.
What does unstable coexistence mean in competition?
Unstable coexistence occurs when neither species can invade from low abundance. The final
outcome depends on starting conditions, and one species usually excludes the other.
Explain the two-species interaction framework.
Species interactions can be classified by the net effect each species has on the other. Effects
can be positive, negative, or neutral, producing interactions such as competition, exploitation,
mutualism, commensalism, amensalism, or neutralism.
Compare competition, exploitation, and mutualism.
Competition is -,- because both species are harmed. Exploitation is +,- because one species
benefits and the other is harmed. Mutualism is +,+ because both species receive net benefits.
Explain why interaction effects are net effects.
An interaction can include both benefits and costs, but it is classified by the overall net result.
For example, mutualism may involve costs, but both species still have a net positive outcome.
What do s1,2 and s2,1 represent?
s1,2 represents the effect of species 2 on species 1. s2,1 represents the effect of species 1 on
species 2.
Answers
Define community.
A community is a group of individuals of different species occupying a particular place at a
particular time.
Compare resources and conditions.
Resources are used up by organisms and their availability changes with the number of
organisms, such as food or nutrients. Conditions affect organisms but are not consumed, such
as temperature or pH.
Define niche.
A niche is the range of biotic and abiotic tolerances and requirements that allow a species to
survive and reproduce.
Compare fundamental and realized niche.
The fundamental niche is where a species could survive and reproduce without interspecific
interactions. The realized niche is where it actually survives and reproduces in the presence
of interspecific interactions.
What does R* represent?
R is the minimum amount of a resource needed to sustain a species. A species with a
lower R is usually the better competitor for that limiting resource.
Explain the most likely outcome of competition for one limiting resource.
In a homogeneous environment with one limiting resource, the species with the lowest R* is
expected to win because it can reduce the resource below the level needed by competitors.
, What is a ZNGI?
A zero net growth isocline is a line showing combinations of species densities or resources
where the population growth rate is zero.
What does stable coexistence mean in competition?
Stable coexistence occurs when both species can invade from low abundance and persist
together. If one species becomes rare, it can increase, helping maintain coexistence.
What does unstable coexistence mean in competition?
Unstable coexistence occurs when neither species can invade from low abundance. The final
outcome depends on starting conditions, and one species usually excludes the other.
Explain the two-species interaction framework.
Species interactions can be classified by the net effect each species has on the other. Effects
can be positive, negative, or neutral, producing interactions such as competition, exploitation,
mutualism, commensalism, amensalism, or neutralism.
Compare competition, exploitation, and mutualism.
Competition is -,- because both species are harmed. Exploitation is +,- because one species
benefits and the other is harmed. Mutualism is +,+ because both species receive net benefits.
Explain why interaction effects are net effects.
An interaction can include both benefits and costs, but it is classified by the overall net result.
For example, mutualism may involve costs, but both species still have a net positive outcome.
What do s1,2 and s2,1 represent?
s1,2 represents the effect of species 2 on species 1. s2,1 represents the effect of species 1 on
species 2.
