I) Development of eye is not a point utilised in classification rather it is an important feature in the evolution. *Evolution of eye was not successfully explained by Darwin. It is the assumption made by the scientists that first eye-like structure could have been a light sensitive spot on the skin. This could have gone through many changes and complexities to form human eye. *There was a simplest light-sensitive spot on the skin in ancestral organisms. *Random changes created a depression in the light sensitive patch making the vision sharper.in animls like planarians *In insects, the light-sensitive spot gradually evolved into special layer with structures like ommatidia. *Later, over a period of time, lens was formed in front of the eye.*Vertebrates and octopuses developed the eye resembling a pin-hole camera. Nerve fibres pass infront of the retina. Cephalopods have an eyes in which nerves are attached to the retina. They do not have a blind spot. Blind spot is present in the retina of the vertebrate eye whereas blind spot is absent in the octopus eye. *Human eye is a complex structure made up of different structures which individually are incapable of vision. Altogether, the lens, the pupil, the iris and the retina make the vision possible.

Common Evolutionary Origin of Eyes
The eyes of Planaria, Insects, Octopus, and Vertebrates showcase a fascinating case of evolutionary adaptation, but their origins differ significantly.
Types of Eyes
- Planaria possess simple eye spots that can detect light but do not form images.
- Insects have compound eyes made up of numerous ommatidia, allowing for a wide field of vision and motion detection.
- Octopuses feature camera-type eyes similar to those of vertebrates, which can focus and form clear images.
- Vertebrates, including humans, have a complex eye structure with a lens, retina, and iris, enabling detailed vision.
Divergent Evolution
- The eyes in these groups arose through different evolutionary pathways:
- Planaria: Eyes evolved for basic light perception, aiding in survival.
- Insects: Compound eyes evolved to enhance motion detection in their environments.
- Octopus: Camera-like eyes developed convergently, showing adaptation to predatory lifestyles.
- Vertebrates: Eyes evolved to improve image resolution and depth perception for navigation and hunting.
Convergent vs. Divergent Evolution
- While some eye structures appear similar (e.g., octopus and vertebrate eyes), this is a result of convergent evolution, where unrelated species develop similar traits due to similar environmental pressures.
- The underlying genetic and developmental mechanisms for eye formation vary widely across these groups.
Conclusion
- In summary, despite the functional similarities of eyes in Planaria, Insects, Octopus, and Vertebrates, they do not share a common evolutionary origin. Instead, they illustrate the principle of convergent evolution, demonstrating how different species adapt to their environments in unique ways.