Samples Environment Environment Q&A

Environment Q&A

636 words 3 page(s)

1. Can Paine effectively argue that there is only one resource in his system? If so, what is it? If not, why not?
The common resource that Paine describes is known as ‘primary space’. He argues effectively that this is necessarily limited because there are only so many surfaces and areas that the species can inhabit.

2. Is there a predator that Paine thinks could allow coexistence of multiple competing species?
Pollicipes polymerus

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a. If so, what is the predator, and does it preferentially eat one of the competing species? Explain your reasoning.
The time for interspecific competitive exclusion is long which makes it hard to ascertain the precise amount of influence this species has.

b. Does it matter to his theory whether the predator feeds preferentially or not? Explain your reasoning.
No, because the predator will always have an effect on the mussel species.

3. What manipulations did Paine do in order to modify the intensity of predation?
The main manipulation used within this study was the experimental removal of the predator Piaster in the Mukkaw Bay area.

a. What were the treatments? How effective were they based on data he presents?
Placing screws in the rock to retain cages, making decisions on what constitutes substratum, calculating a coefficient of variation to measure the distance between the species boundary and the screw
They were very effective and allowed the prey to dominate the area.

b. Did he have controls for the manipulations? If so, what were they?
Yes, areas that did not have Piaster removed.

c. How adequate was his replication? Explain your reasoning.
Very accurate because it represented the natural change in population density over time.
4. From Table 5:
a. What were the most impressive differences between the experimental and
control plots?
The most obvious difference is the % utilization of space by Mytilus californianus which was 5 or less % in the control areas and over 95% in the areas where the starfish species was removed. Another difference was the % utilization of space by Lithothamnium species which was 16% in one control and 4% in a removal area.

b. Do the results confirm or falsify Paine’s hypothesis, or are the results
ambiguous? Based on the data presented why do you think so?
The results confirm the hypothesis but more research needs to be done about differences between natural habitats containing the species to give real-world data.
c. Do you think Paine’s sample sizes were adequate? Why or why not?
The sample sizes themselves were fairly small and spread over a number of different areas in different years. There was more evidence from the removal areas than the control, which makes it hard to give an overall comparison.

5. What evidence is there in the tables and figures that Paine has correctly identified the competitively dominant species in his system? Explain your reasoning.
It is interesting to consider the fact that Mytilus might be the dominant species in the area from a competitive perspective, because it does not happen in a natural scenario but when the predator is removed. This suggests that the species has a skill for utilizing space but cannot exercise it in a natural scenario, which means that it is not naturally dominant and so doesn’t provide any real-world data.
6. What evidence does Paine present that competition is important in this system?
The main evidence that is presented within this paper that competition is important is the % utilization of space by M. californianus in the situation where the main predator is removed. This is not only because of the lack of predation but also the increase of space available.

7. Are there parallels in this paper to the results reported by Connell in the Balanus/Chthamalus paper? If so, what are they? Explain your reasoning.
The main parallel between the two papers is that competition is important, although the type of competition varies.