Describe the changes in jaw structure and hearing apparatus that accompanied the evolutionary transition from reptiles to mammals. They are collectively known as the ossicles. Describe or diagram the two basic types of mammary glands.
Infants suck on the nipple to obtain milk.
I also gave partial credit if you described the mammary gland of the monotremes, which contains no external projection for suckling but which instead has ducts that lead directly to the skin surface. Milk production is stimulated by the hormones Prolactin and Growth Hormone and by the sensory stimulation of infants suckling. While Estrogen and Progesterone contribute to the development of the mammary gland during late pregnancy, it is only after levels of E and P drop after parturition that milk production begins. Correct identification of the hormones responsible for milk production was worth 1 point and the sensory stimulus for milk production was worth 1 point. Mammals show many variations on the basic reproductive pattern, including delayed fertilization, delayed implantation and spontaneous abortion.