Final answer:
Puppies' eyes and ears typically open during the second to fourth week after birth, marking a crucial period for sensory development and the establishment of neural connections in the brain.
Step-by-step explanation:
Puppies' eyes and ears are closed at birth, a feature they share with many other mammals. During development, puppies undergo various stages where different physical and neurological systems begin to take shape. The eyes and ears of puppies usually open during developmental weeks 2 to 4 after birth. This is a critical period, as sensory experiences during these early stages of development are crucial for the proper formation of neural connections in the brain. If puppies are deprived of sensory input during this time, it can result in underdeveloped areas in their sensory cortex, as was shown in studies with kittens where one eye was sutured closed.
This development period is essential not only for puppies but for a variety of mammals, as it marks the development of the visual and auditory systems that are vital for their eventual interaction with the environment. By the end of this period, puppies typically have fully opened eyes and ears, allowing them to process visual and auditory information and start to explore their surroundings more fully.