we have both sets of hypotheses:|
1. If one species of mussel is removed, then the other species
will increase in numbers.
2. If mussels are moved to an area with another saline content,
several of them will die compared to if they were moved to areas with the same
To be able to distinguish among alternative hypotheses
derived from the various models that might explain our observations, we must carry out the relevant experiments. We have to experimentally create conditions so that the
different predictions will be able to occur. The relevant experiments are those that include
these conditions and then are compared with sites that continue to be in
the same condition as those we initially observed. We accordingly assume
greater changes in those areas that we changed in accordance with the hypothesis
compared to areas that have not been changed.
To test the first hypothesis we must initially
reduce the number of individuals of one of the mussel species from certain areas so we can see if there
will be a change in the number of mussels of the other species in these areas. But we also need controls
to be able to see if an eventual increase in numbers within the experiment
area was dependent of the reduction of the other species. There can for example
occur a large scale increase in the numbers of mussels along the coast that was not
dependent of the removal of the supposed competitors in the experimental
areas. Therefore, we have to compare what occurs to the number of mussels within the experimental
areas with what occurs within the control areas, where supposed competitors are still present.
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