<span>a. Acoelomates. Flatworm is a type of acoelomate animal; they have no body cavity or ceolom but they have </span>mesenchyme in their body cavity that surrounds the gut and organs in one solid body.
Hey! they are usually single celled!
hope this helped xoxo
<span>descriptions of the number, size, and arrangement of parts of the organism.</span>
This is true.
An easy way to remember this is that Cis-acting elements are physically linked to a set of structural genes. So promoters and operators are physically linked to the gene they express. They are cis acting because they are on the same strand as the structural gene they control.
On the other side, trans means that they can come from somewhere else and act. A good example of this would be regulatory proteins. These could be expressed somewhere else (or on a different strand) and then bind and affect transcription.
The process they would undergo is metamorphosis.
