The reason we see only a particular range of the electromagnetic (EM) spectrum, known as the visible light spectrum, is indeed related to the evolution of our eyes. The evolution of vision in organisms is primarily shaped by the available light sources and the selective advantage it provides.
The visible light spectrum ranges from approximately 400 to 700 nanometers (nm) in wavelength and corresponds to the colors we can perceive, such as violet, blue, green, yellow, orange, and red. This range is well-suited for our visual perception due to various factors, including the following:
Sunlight composition: The Sun is the primary source of light on Earth, and its emission spectrum is strongest in the visible range. Organisms that evolved to perceive this range of light would have been better equipped to navigate their environment and locate resources.
Atmospheric transmission: Earth's atmosphere selectively transmits and scatters certain wavelengths of light. The visible light spectrum is relatively unaffected by the Earth's atmosphere, allowing it to reach the surface without significant absorption or dispersion. Other regions of the EM spectrum, such as ultraviolet and infrared, are absorbed or scattered more strongly, making them less suitable for long-range vision.
Photoreceptor sensitivity: Our eyes contain specialized cells called photoreceptors that convert light into electrical signals. The two primary types of photoreceptors in humans are rods and cones. Rods are more sensitive to dim light and primarily contribute to low-light and peripheral vision, while cones are responsible for color perception and function best in brighter light conditions. The sensitivity of our photoreceptors aligns with the intensity of light in the visible spectrum.
Energy considerations: Evolutionarily, it is advantageous for organisms to maximize energy efficiency. The visible light spectrum represents a balance between energy absorption and energy loss. Too high-energy radiation, such as ultraviolet or X-rays, can be damaging to biological tissues, while too low-energy radiation, such as infrared, may not carry enough energy to trigger the necessary biochemical processes for vision.
It's important to note that different organisms have evolved different visual systems, each adapted to their specific ecological niche. For instance, some animals, like bees and birds, can perceive ultraviolet light, which aids in identifying flowers or spotting predators. Conversely, some nocturnal animals have evolved heightened sensitivity to lower light levels, including some capacity to perceive infrared.
In summary, the visible light spectrum corresponds to the range of light that is abundant in our environment and is best suited for efficient vision. The evolution of our eyes and photoreceptor sensitivity is aligned with the available light sources and the ecological needs of our ancestors, providing selective advantages for survival and reproductive success.