Unit 2: Organisms & Evolution
Key Area 5: Parasitism - The Niche
Starter
Success Criteria
a)i) Niche
Niche
Niche - The niche of an organism is the functional role that it plays within an ecosystem.
An ecological niche is a multi-dimensional summary of tolerances and requirements of a species.
Multidimensional
Requirements
Tolerances
Niche
Fundamental and realised niches
A species has a fundamental niche that it occupies in the absence of any interspecific competition.
A realised niche is occupied in response to interspecific competition.
Things to consider:
Niche
The diagram below shows the distribution of two species of barnacle. The fundamental and realised niches of the two species are shown by the vertical lines W,X,Y and Z. The realised niche of species 2 is line Z.
Competitive exclusion
Competitive exclusion principle
When 2 organisms have a very similar niche competitive exclusion can take place. This causes one of the populations to decrease to local extinction.
Resource Partitioning
Resource partitioning
Where the realised niches are sufficiently different, potential competitors can co-exist by resource partitioning.
E.g. Organisms forage for different foods to reduce competition.
Clostridium difficile - case study
Watch the video. Using the information we have learned so far, Explain why this method works in treating the condition?
Symbiosis
Symbiosis
Symbiotic relationships are co-evolved and specific intimate
relationships between members of two different species.
Discuss: Think about the parasite-host relationship? How does it differ from the predator prey relationship?
Discuss: Think about the parasite-host relationship? How does it differ from the predator prey relationship?
a)ii) The parasite niche
Niche
Parasitism is a symbiotic interaction between a parasite and its host ( + / - ).
A parasite gains benefit in terms of nutrients at the expense of its host.
Unlike in a predator–prey relationship, the reproductive potential of the parasite is greater than that of the host.
Niche
An ectoparasite lives on the surface of its host, whereas an endoparasite lives within the tissues of its host.
How parasites exploit the host
Niche
Most parasites have a narrow (specialised) niche as they are very host-specific .
As the host provides so many of the parasite’s needs, many parasites are degenerate, lacking structures and organs found in other organisms. For example, tape worms lack a digestive system so live in the intestines of animals to absorb their digested food.
Research
Research a parasite of your choice and create an information fact file to inform the public on the parasite. You may want to include information such as:
Success Criteria