(i) ‘Planaria, insects, octopus and vertebrates all have eyes. Can we group eyes of these animals together to establish a common evolutionary origin? Justify your answer. (ii) “Birds have evolved from reptiles”. State evidence to prove the statement.

(i) Grouping of Eyes in Planaria, Insects, Octopus, and Vertebrates

No, we cannot group the eyes of these animals together to establish a single, common evolutionary origin.

Justification:

• Analogous Organs: The eyes of these diverse animal groups are classic examples of analogous organs. They perform the same basic function (vision) but have completely different structural designs, tissue origins, and evolutionary histories.
• Structural Differences:
• Planaria has extremely simple "eye-spots" which are merely light-detecting photoreceptor patches.
• Insects possess compound eyes made of thousands of tiny independent units called ommatidia.
• Octopus and Vertebrates have complex, single-lens camera-type eyes, but even their retinal structures and developmental pathways differ significantly.
• Conclusion: Since their structures are fundamentally different, they do not share a common ancestral eye design. Instead, they evolved independently in response to a common environmental need (the utility of detecting light/vision), which is a process known as convergent evolution.

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(ii) Evidence that "Birds have evolved from reptiles"

There is compelling fossil and anatomical evidence to prove that birds evolved from reptilian ancestors:

1. Fossil Evidence (Archaeopteryx):

The fossil of Archaeopteryx* serves as a "connecting link" between reptiles and birds.

• It exhibited avian (bird-like) features such as feathered wings and a wishbone.
• Simultaneously, it retained distinct reptilian features such as teeth in its jaws, claws on its free fingers, and a long bony tail.

1. Evolution of Feathers:

• Feathers first evolved in some reptiles (like theropod dinosaurs) not for flight, but to provide insulation and keep them warm in cold weather.
• Later, during the course of evolution, birds adapted these pre-existing feathers for the purpose of flight. This shows that birds are closely related to reptiles.