Question

(a) Give the evidence that the birds have evolved from reptiles.

(b) Insects, Octopus, Planaria and vertebrates possess eyes. Can we group these animals together on the basis of eyes that they possess?

Justify your answer giving reason.

Answer 1

a) Birds have evolved from reptiles. The evidence for the same is provided from palaeontological studies.For example, Archaeopteryx a missing link between reptiles and birds. It was a flightless bird which shows the characters of both reptiles and birds.

Reptilian characters:

1. Long tail

2. Pelvis resembling that of reptiles

3. Cranium similar to reptilian skull

4. Two claws on the limbs.

Avian characters:

1. Presence of feathers

2. Reduced fingers

3. wings resembling birds

4. Flexible first toe

b) No, insects, octopus, Planaria and vertebrate cannot be grouped together on the basis of eyes as eyes cannot be used as a feature for classification. Eyes can be used to study the evolutionary process. The primitive eye like structure was just like a light-sensitive spot on the skin. It underwent changes that lead to the formation of complex eyes in vertebrates. In insects, it changed into ommatidia which formed the compound eyes in them to form a sharp image. Later on, lens formation occurred. In octopus, nerves are attached to retina but there is no blind spot. Human eyes are most complex showing the presence of iris, pupil, ciliary body and lens.