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

Hint: The word evolution is derived from the Latin word ‘evolvere. It means to ‘unroll’ or ‘unfold’. Charles Darwin gave the concept of evolution. It is defined as a gradual change in the forms of life from simple to complex that results in the present day diversity of life. Various evidences are available to support evolution.

Complete answer:
(a) Fossils provide us direct evidence of the types of organisms (Plants, animals and microbes) that existed at a particular geological time and help us to reconstruct the evolutionary process. The fossil Archaeopteryx is the connecting link between the reptiles and birds. It looks like birds but has many other features like reptiles. It was a flightless bird which shows the characters of both reptiles and birds.
Reptilian characters:
Presence of long tail with caudal vertebrae
Presence of homodont teeth in jaws
Eyes are provided with sclerotic ossicles
Scales are present.
Fore limbs are provided with free fingers tipped with claws.
Avian (Bird-like) characters:
Presence of feathers on the body.
Forelimbs are modified into wings.
Four toes in the foot adapted for perching.
Presence of beak
Bones in the skull are intimately fused and bones of limbs and girdles are bird-like.

(b) Based on the presence of eyes in insects, octopus, Planaria and vertebrates, they cannot be placed in one group and the eye feature cannot be considered for classification.
Eyes can only be used to study the evolutionary process as in Planaria, eyes are rudimentary consists of a few photosensitive cells which detect light. In insects, compound eyes with mosaic vision are present. In the eyes of Octopus, a member of Mollusca phylum, nerves are attached to the retina but there is no blind spot and in vertebrates eyes have well-developed eyes with iris, pupil, ciliary body and lens.

Note: The paleontological studies of the fossil Archaeopteryx is the link between reptiles and birds. This provides evidence that birds have originated from the reptiles.
The structure of the eyes in Insects, octopus, Planaria and vertebrates are different in structure and function. They have originated separately.