NOTE's
This question should be used as a practice exercise for Ecological Niche analysis and understanding. It also combines elements of animal physiology and biological principles.
There is more in the way of explanatory notes and information than would be in an examination question.
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An ecological niche is a concept (an explanation) that aims to describe the rôle an organism plays in its community.
That rôle is not its ‘address' as it is sometimes called nor is the ecological niche the organism's ‘occupation'.
In simple terms, an ecological niche could be that a barn owl is a predator whilst a field mouse is a prey organism. However, that example is far too simplified for A Level students and a greater depth of insight is needed as is the case for all ecological studies.
References. Tivy & O'Hare (1981)1 describes a niche in terms of an organism's feeding habit. Roberts, King & Reiss (1994)2 also appear to concur with the idea that niche refers to an organism's food.
1. Tivy, J. & O'Hare, G. (1981) Human Impact on the Ecosystem. Oliver & Boyd, London ISBN 0 05 003203 8
2. Roberts, M., King, T. & Reiss, M. (1994) Practical Biology for Advanced Level. Nelson, Walton-on-Thames ISBN 0 17 448225 6
Question 2 contains a number of tables of information as well as several questions. Take your time and study each table carefully before attempting a question.
- Ask yourself "What does this table tell me?" or, "What's this table all about?"
- Ask yourself which biological principles and aspects of animal physiology are involved within the question as a whole
QUESTION 2
Tits, Competition & Niches
Information:
The tit family comprises a number of small insect-eating birds. A classic characteristic of the tit family is that all members can hang upside down to feed. Most species common to the UK breed in woodland areas but in winter months, are a familiar sight in gardens hanging upside down from bird feeders.
An A-Level Human Biology student decided to carry out a practical investigation for her A2 coursework. She chose to study the feeding habits of three species of tit: the blue tit (Parus minor), the Great Tit (Parus major) & the Coal tit (Parus ater). These birds and the investigation, were chosen as the student had observed in the garden of her home.
The student entitled her coursework "Ecological competition & Niches". After doing background research, she decided to test her hypothesis by constructing two types of bird feeder: a peanut feeder suspended by a wire hook and another suspended by a length of elastic. The hypothesis was that the structure of the bird feeder would determine the success of feeding by certain species. This is turn, would be related to the ecological niche the species occupied in the tit family.
Data were recorded during the period of December. Tables were constructed of the data as follows:
Table 1 Peanut feeder suspended by a wire hook - number of times a bird was observed (aggressive behaviour indicated by a species leaving the feeder)
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Table 2 Peanut feeder suspended by length of elastic - number of times a bird was observed (aggressive behaviour indicated by a species leaving the feeder)
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a) Referring to tables 1 and 2, describe the results of the competition between Parus major and Parus minor when each species was competing for food from the feeder suspended by a wire hook.
[ 1 ]
b) How many observations were made of each pair of species (reference to question 2a) ) on each feeder? (HINT: This is calculated by summing the total observations at each feeder and dividing by the number of species).
[ 1 ]
c) Explain the advantage of collecting data in this way. (HINT: consider how competition could be compared if the encounter were of an uneven distribution e.g. 8 of one species and 15 of another).
[ 1 ]
Further work by the student:
The student decided to extend her investigation by recording data to show how much time each species spent at a particular type of feeding location. The locations were chosen from selected areas in her garden after the feeders were removed.
She constructed a table of data as shown in Table 3:
Table 3. Percentage of time spent feeding at different types of feeding site.
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The student also included in her results the mean height of feeding above ground and, the mean body mass for each species. The later data she obtained from the local wildlife trust. She constructed Tables 4 and 5 for those data.
Table 4. Mean height of feeding above ground for each species.
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Table 5. Mean body mass (g) of the species.
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d) Describe and suggest explanations for the results of competition between the three species on the two different feeders. You will need to refer to and consider the information contained in all the tables to answer this question.
[ 4 ]
From the student's research and background information, she formulated a table (Table 6) describing the relative energy requirements for Parus major and Parus minor. The energy requirements appeared be linked to body mass and feeding with the latter apparently being correlated to daylight hours.
Table 6. Data showing the energy requirements, body mass and percentage of daylight spent feeding for Parus major & Parus minor.
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e) Calculate the figures for relative energy requirement. (HINT: this is a calculation related to total energy requirement and body mass)
[ 1 ]
f) Using the information in Table 6, suggest why Parus minor:
(i) has a greater relative energy requirement than Parus major
[ 2 ]
(ii) feeds for a greater % of daylight than Parus major.
[ 1 ]
g) Great tits and blue tits are found over a large area of Europe although Great tits
are found further north than blue tits. Using the information in Table 6 and your
answers to questions f) and g), suggest reasons for the wider distribution of great tits.
[ 3 ]
[Total: 14 ]
