Question

An ecologist observes that the diet of a bird species consists primarily of large grass seeds (as opposed to smaller grass seeds or the seeds of other herbaceous plants found in the area). He hypothesizes that the birds are choosing the larger seeds because they have a higher concentrations of nitrogen than do other types of seeds at the site. To test the hypothesis, the ecologist compares the large grass seeds with the other types of seeds, and the results clearly show that the large grass seeds do indeed have a much higher concentration of nitrogen. Did the ecologist prove the hypothesis to be true? Can he conclude that the birds select the larger grass seeds because of their higher concentrations of nitrogen? Why or why not? If you suspect an additional factor may involve, state your hypothesis and the design of an experiment to test your hypothesis

Answer 1

Lets understand the given passage.

An ecologist observes that the diet of a bird species consists primarily of large grass seeds (as opposed to smaller grass seeds or the seeds of other herbaceous plants found in the area).

He hypothesizes that the birds are choosing the larger seeds because they have a higher concentrations of nitrogen than do other types of seeds at the site.

To test the hypothesis, the ecologist compares the large grass seeds with the other types of seeds, and the results clearly show that the large grass seeds do indeed have a much higher concentration of nitrogen.

No, he cannot conclude that the birds select the larger grass seeds because of their higher concentrations of nitrogen. The hypothesis testing done by the ecologist is incomplete as he failed to set up a control in the experiment. The control would have been the birds feeding on large seeds that lack or are low on nitrogen content. This will establish a relation between the bird's diet and the size of the seeds and the nitrogen content of the seeds. It could be true that birds do not care about the nitrogen content but simply prefer larger seed sizes.

Another problem associated with his field experiment is the failure in noting the beak sizes of the birds. The beak size and shape enable a bird to break and eat seeds. Larger beaks fail at breaking open smaller seeds. This observation would add bird beak size as another variable of the experiment.