Final answer:
Animals generally have two eyes to enhance depth perception and a wider field of view, which are essential for their survival. Moreover, the complexity and number of eyes can vary among species based on their specific ecological needs and evolutionary background. Cone cell variety across species also results in different color perception capabilities.
Step-by-step explanation:
Animals with eyes tend to have two of them primarily because this arrangement enhances depth perception and field of view, aiding in an animal's ability to interact with its environment. Having two eyes allows for binocular vision, where each eye sends a slightly different image to the brain, which interprets these images to perceive depth, a critical factor in judging distances and navigating the spatial layout of the surroundings. Additionally, two eyes positioned on either side of the head can offer a wider field of view, increasing the ability to detect motion and predators or prey.
However, the number and complexity of eyes depend on the ecological niche and evolutionary history of the species. For example, certain insects and marine animals like cubozoans have a more complex arrangement of eyes that serves their specific needs, even though they lack a distinct brain. These specialized visual systems allow these animals to successfully hunt or navigate their environments, despite the increased complexity.
Color perception varies between different animal species based on the number of cone cells in their eyes. While most mammals have two types of cones, resulting in less vivid color perception, other animals like birds and insects may have more, allowing them to perceive a greater number of hues.