Question

Give a definition of a PREADAPTATION in the context of vertebrate evolution and explain examples in two different vertebrate classes in which this has occurred. 300 words worth of questions. 10 marks

Answer 1

PREADAPTATION

It is a character or the condition of possessing a character that takes on a function when none previously existed or that differs from its original function

• It refers to a large change in function accomplished with little or no change in structure .
• It refers to the possibility of a characteristic to adopt a new biological function without evolutionary modification. This phenomenon is usually known as “preadaptation.”

Preadaptation can refer both to anatomical or behavioral characteristics.

Anatomical

• Bird feathers.
• At first, birds' feathers were essentially for heat insulation rather than an adaptation for flight; this initial evolutionary purpose for warmth represents a preadaptation for flight.

Behavioural

• Subdominant wolves licking the mouths of lead wolves as a sign of submissiveness.
• This trait can be explained as wolf pups licking the faces of adults to encourage them to regurgitate food.

Another example is the lungs of many basal fish, which evolved into the lungs of terrestrial vertebrates but also underwent exaptation to become the gas bladder, a buoyancy control organ, in derived fish.

A third is the repurposing of two of the three bones in the reptilian jaw to become the malleus and incus of the mammalian ear, leaving the mammalian jaw with just one hinge.

The possession by a species or other group of characteristics that may favour survival in a changed environment, such as the limblike fins of crossopterygian fishes, which are preadaptation to terrestrial life