Answer:
Because no herbivores would want to eat it, and it could ward most predators away easier.
Explanation:
Larger lenses are heavier, and tend to sag under their own weight, ruining the image quality as the lenses distort. The long mounting tubes are hard to make mechanically stiff, and so they tend to flex under the weight of the lens, making it hard to keep the optics in alignment.
First of, they are in two different phylum. Flat worms are in the planarian phylum while, Porifera is the sponges phylum. Sponge has no organs, and can reproduce asexually. Many flat worms are parasites while no sponges are. Another thing is sponges have no symmetry while flat worms have bilateral symmetry. Hmmm what else... on yes flat worms have one body opening while, i not 100% sure sponges have two.
The answer is d b/c smaller cells will have greater surface area to volume ratio
