Chapter 34, Problem 8TYU

SCIENTIFIC INQUIRY • DRAW IT As a consequence of size alone, larger organisms tend to have larger brains than smaller organisms. However, some organisms have brains that are considerably larger than expected for their size. There are high energetic costs associated with the development and mainte- nance of brains that are large relative to body size.

1. (a) The fossil record documents trends in which brains that are large relative to body size evolved in certain lineages, including hominins. In such lineages, what can you infer about the costs and benefits of large brains?
2. (b) Hypothesize how natural selection might favor the evolution of large brains despite their high maintenance costs.
3. (c) Data for 14 bird species are listed below. Graph the data, placing deviation from expected brain size on the x-axis and mortality rate 011 the y-axis. What can you conclude about the relationship between brain size and mortality?

Deviation from Expected Brain Size*	-2.4	-2.1	-2.0	-1.8	-1.0	0.0	0.3	0.7	1.2	1.3	2.0	2.3	3.0	3.2
Mortality Rate	0.9	0.7	0.5	0.9	0.4	0.7	0.8	0.4	0.8	0.3	0.6	0.6	0.3	0.6