recap

52.3 recap

Genetics can determine what behaviors can be learned, and hormones can determine the sensitive period when they can be learned as well as the motivational states that trigger their expression. Imprinting ensures the ability of individuals to recognize other individuals or species at a later time. Some capacity for variation of genetically determined and imprinted behaviors enables behavior to be shaped by social context.

learning outcomes

You should be able to:

  • Explain how hormones can affect the timing and expression of behavior.

  • Describe the evidence supporting the claim that genetics are important in bird singing behavior.

  • Explain the evolutionary benefit of variability in the singing behavior of a bird species.

Question 1

Why is female considered to be the default pathway for the development of sexual behavior in rats?

If neonatal genetic male and female rats are gonadectomized, they both develop female sexual responses to estrogen as adults, and they are both unresponsive to testosterone stimulation as adults.

Question 2

Explain why a songbird deafened in adulthood can sing its song, but a songbird deafened before reaching sexual maturity cannot.

The songbird will not sing its song until it reaches sexual maturity, and at that time it has to learn to sing the template it formed as a nestling. To learn, it must practice and hear itself sing. Once its song has crystalized, the bird will be able to sing it even if deafened.

Question 3

Under what conditions might variability in a species-specific behavior be adaptive or not be adaptive?

Variability in a species-specific behavior such as birdsong might be adaptive if it enables an individual to establish identity with a different local population or to create a new song feature that enhances its attractiveness to potential mates. Variability in this same species-specific behavior could be maladaptive if it detracts from individual recognition. For example, in a situation in which an individual is returning to its nesting grounds to mate with a previously established mate or to feed offspring, it is important to be able to establish individual identity.

Complex behaviors are the product of interactions of genetic, physiological, and environmental factors. Many genes are involved in shaping behavior, and therefore there are multiple opportunities for selection to favor behavioral modifications. Questions about how changes in behavior adapt animals to environmental conditions are the province of an evolution-based field called behavioral ecology.