KEY POINTS

Reproductive Cycles

1. The two types of reproductive cycles are estrous and menstrual.

Puberty and Reproductive Senescence

1. Puberty is the time at which animals first release mature germ cells.

2. Reproductive senescence in primates occurs because of ovarian inadequacy, not inadequacy of gonadotropin secretion.

Sexual Behavior

1. Sexual receptivity is keyed by the hormones estrogen and gonadotropin-releasing hormone in the female and testosterone in the male.

External Factors Controlling Reproductive Cycles

1. Photoperiod, lactation, nutrition, and animal interaction are important factors that affect reproduction.

2. Inadequate nutrition results in ovarian inactivity, especially in cattle.