1
ECOL111 Module 3 - Species Interactions Questions with
Answers (100% Correct Answers)
What are the two main mechanisms by which interspecific competition
can occur and what do they mean? Answer: Exploitation competition -
Indirect competition through shared resources. When a species uses a
resource, there are less resources available for other species, there is no
active competition.
Interference competition - Direct competition involving one species
actively preventing access to resources, or inhibiting growth or
survival of another species. This doesn't just involve behaviour
meaning it can involve plants as well. An example of this is
allelochemicals being secreted by some plants to inhibit the growth
rate of other species.
What is the difference between functional and numerical responses?
Answer: Functional responses - where the use of resources by a species
is changed based on the presence of another species. A change in the
behaviour or physiology of a species.
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,2
Numerical response - where the presence of one species is lower when
the competitor is present, than if they are not. This is generally easier
to recognise as competition by ecologists.
Explain when and why competitive exclusion might occur. Answer:
The superior competitor could cause the extinction of the other
competitor, but this is a very extreme occasion. It's rare because:
- Competitive advantages may depend on conditions
- The environment is patchy
- Species can adjust their niche.
These factors suggest that extinction due to competition does not occur
very often and only in extreme cases.
Describe evolution in the face of sustained competition. Answer:
Where we see a highly diverse community (e.g. fish on a coral reef
very high biodiversity) there must have been strong competition and
so they have evolved super specialised niches so that these species
don't have to compete for resources.
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, 3
Sometimes due to a long history of fundamental responses and
evolution, some species may perform better in the presence of a
(historical) competitor due to niche modifications.
Explain the role of niche complementarity in structuring communities.
Answer: Niche complementarity is where, due to a history of
competition, partitioning of resources and reduced niche overlap
occurs. This is because of functional responses and evolution causes
different dimensions of niches to shift between species and coexisting
can occur.
What are the different types of consumers and how do they differ?
Answer: Predators
-Invariably kill their prey during attack
-Consume several prey in their lifetime
Grazers (herbivores)
© 2025 All rights reserved
ECOL111 Module 3 - Species Interactions Questions with
Answers (100% Correct Answers)
What are the two main mechanisms by which interspecific competition
can occur and what do they mean? Answer: Exploitation competition -
Indirect competition through shared resources. When a species uses a
resource, there are less resources available for other species, there is no
active competition.
Interference competition - Direct competition involving one species
actively preventing access to resources, or inhibiting growth or
survival of another species. This doesn't just involve behaviour
meaning it can involve plants as well. An example of this is
allelochemicals being secreted by some plants to inhibit the growth
rate of other species.
What is the difference between functional and numerical responses?
Answer: Functional responses - where the use of resources by a species
is changed based on the presence of another species. A change in the
behaviour or physiology of a species.
© 2025 All rights reserved
,2
Numerical response - where the presence of one species is lower when
the competitor is present, than if they are not. This is generally easier
to recognise as competition by ecologists.
Explain when and why competitive exclusion might occur. Answer:
The superior competitor could cause the extinction of the other
competitor, but this is a very extreme occasion. It's rare because:
- Competitive advantages may depend on conditions
- The environment is patchy
- Species can adjust their niche.
These factors suggest that extinction due to competition does not occur
very often and only in extreme cases.
Describe evolution in the face of sustained competition. Answer:
Where we see a highly diverse community (e.g. fish on a coral reef
very high biodiversity) there must have been strong competition and
so they have evolved super specialised niches so that these species
don't have to compete for resources.
© 2025 All rights reserved
, 3
Sometimes due to a long history of fundamental responses and
evolution, some species may perform better in the presence of a
(historical) competitor due to niche modifications.
Explain the role of niche complementarity in structuring communities.
Answer: Niche complementarity is where, due to a history of
competition, partitioning of resources and reduced niche overlap
occurs. This is because of functional responses and evolution causes
different dimensions of niches to shift between species and coexisting
can occur.
What are the different types of consumers and how do they differ?
Answer: Predators
-Invariably kill their prey during attack
-Consume several prey in their lifetime
Grazers (herbivores)
© 2025 All rights reserved
