When considering the evolution of the eye, of the following features, which was likely the first to evolve?

• A. A simple lens.
• B. A cup-like shape.
• C. A flat layer of photoreceptors.
• D. An enclosed spheroid organ.

Answer: (C)

Verified step by step guidance

1. Understand the concept of photoreceptors: Photoreceptors are specialized cells in organisms that respond to light. They are crucial for the development of vision and are found in various forms across different species.
2. Consider the evolutionary process: Evolution often proceeds from simple to complex structures. In the case of the eye, simpler forms would have evolved first, providing basic light detection capabilities.
3. Identify the simplest structure: Among the options given, a flat layer of photoreceptors represents the most basic form. This structure allows organisms to detect light without forming images, which is a fundamental step in the evolution of vision.
4. Compare with other features: A cup-like shape, a simple lens, and an enclosed spheroid organ are more complex structures that would have evolved later to enhance image formation and focus.
5. Conclude the evolutionary sequence: Recognize that the flat layer of photoreceptors likely evolved first, providing the foundation for more complex eye structures to develop over time.