Q28.4-2CC - Campbell Biology

Question

Why is it accurate to say that Ulva is truly multicellular but Caulerpa is not?

Step-by-Step Solution

Answer

The multicellular body of Ulva is differentiated into two types of structures; a leaf-like blade and a root-like holdfast. In contrast, the multicellular body of Caulerpa is not differentiated into distinct body parts. The presence of differentiation makes Ulva truly multicellular.

Step 1: Diversity in algae

Algae are the protist organisms that have the potential to photosynthesize. These organisms mainly inhabit aquatic regions and are mainly classified into distinct groups based upon their pigment differences. 

As per the primary photosynthetic pigment, algae are grouped as brown algae, green algae, and red algae.

Step 2: Multicellularity in green algae

The green algae are members that contain chlorophyll as the primary photosynthetic pigment; the body color is also attributed to this pigment. These organisms produce flagellated gametic cells and can have a unicellular or multicellular body structure. The multicellular alga has more than one cell in the body.

Step 3: Multicellularity in Ulva and Caulerpa

Ulva and Caulerpa are both multicellular members of green algae, but Ulva is considered truly multicellular, while Caulerpa is not. The reason behind this is the difference in body structure. 

Ulva has a well-differentiated body with two distinct structures; a leaf-like blade and holdfast, which is root-like. In contrast, the body of Caulerpa lacks differentiation, and despite having multiple cells, its body structure resembles a single cell of large size.