1.1 Reflections on Two Major Developmental Issues

Sensory systems enable organisms to obtain needed information. Consider:

Figure 1.1: This is Image Asset 2

• A frog, which feeds on flying insects, has eyes with receptortdrdn5cy5BC59sF9 cells that fire only in response to small, dark, moving objects. A frog could starve to death knee-deep in motionless flies. But let one zoom by and the frog's "bug detector" cells snap awake.
• A maleoSDqALG43KqdJCGsbX7ytA== silkworm moth has receptors so sensitive to the odor of the female sex-attractant that a single female silkworm moth need release only a billionth of an ounce per second to attract every male silkworm moth within a mile. That is why there continue to be silkworms.
• We are similarly designed to detect what are, for us, the important features of our environments. Our ears are most sensitive to sound frequencies that include human voice consonants and a baby's cry.

Nature's sensory gifts suit each recipient's needs.