3. Biologists Jamie Smith and André Dhondt investigated the heritability of beak

Question

3. Biologists Jamie Smith and André Dhondt investigated the heritability of beak depth in song sparrows (Melospiza melodia) by means of an interesting field experiment. They collected eggs and nestlings from their study population and moved them into the nests of randomly chosen foster parents. When the chicks were full grown, Smith and Dhondt captured the young sparrows, measured their bill depth, and calculated midoffsprin values for the youngsters and midparent values for both their foster and biological parents. The results are shown in the figures below: y 0.18x+6.86 y 0.98x -0.01 6.2 6.2 .8 ? 5.8 5.8 5.4 5.4 5.4 5.8 6.2 Foster midparent beak depth (mm) 5.8 6.2 gical midparent ceak depth (mm) A. Why did Smith and Dhondt go to the trouble of cross-fostering eggs and nestlings? In other words, how did cross-fostering contribute to the goal of the study- determining the heritability of variation in bill depth-and why was cross-fostering superior to simply letting parents raise their own offspring? Briefly explain. (2 points) B. Does variation in beak depth in song sparrows have high heritability, or does variation in beak depth appear to result primarily from variation in the rearing environment? Briefly justify your response and explain how the data shown in graphs A and B support your answer. (2 points

Explanation / Answer

A) fostering helped to ensure that the shape of beak was not a result of some temporary environmental effect, which case the beak shape should be altered with change if surroundings, diet, habitat, etc. Upbringing by the parents would not bring in any such change and the beaks would stay the way they are as their structure is no longer challenged.

B) in a correlation graph, when the tread line is headed up indicates there is positive correlation between the pair of attributes, when it's horizontal it tells us that there no .correlation while a down facing tread line is a demarcation of negative correlation. Hence the left graph shows no correlation while when one observed the 2nd graph, one can appreciate the dots in positive correlation. Hence, inspite of rearing with foster parents, beak depths of the offspring significantly matched or correlated with that of the parents (biological). Therefore its heritable and not much detected by the environment or surroundings.

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