Q47.2-1CC. - Campbell Biology

Question

In the frog embryo, convergent extension elongates the notochord. Explain how the words convergent and extension apply to this process.

Step-by-Step Solution

Answer

In the embryo of frogs, convergence and extension go hand in hand. The cells present in the notochord get inwards, that is, towards the embryo's center, and hence converge them. The cells then rearrange themselves in such a way that the notochord elongates of undergoes extension.

Step 1: Organogenesis

Organogenesis is a process through which the germ layers of the embryo produce rudimentary organs. In some organisms, the cells of the germ layers have designated roles, and hence their fate is predetermined. However, in some organisms, it is not predetermined.

Step 2: Morphogenic movement of the cell

The migration of certain cells from their place of origin to different places within the embryo is referred to as morphogenic movement. The type of movement is essential for the development of the embryo and also for the proper formation of organs.

Step 3: Convergent extension

A convergent extension is a form of morphogenic movement or rearrangement exhibited by the cells of the frog's embryo. This type of morphogenic movement causes the cells to redirect themselves to the midline and hence converge. 

The cells then rearrange themselves by narrowing and lengthening, causing extension of the notochord.