Do members of the same phylum share more characteristics than members of the same class?​

No, they don't.

Explanation:

In the taxonomic rank (Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species-- in that order) because phylum comes before class, it means it covers a broader spectrum of organisms. So, the traits are less specific. As you narrow it down, the members of the rank will share more and more traits in common.

Here is an example:

Humans are a member of the phylum chordata. All members of phylum chordata share the same 5 traits at some point in their lifetime. (Some only show the traits when they are embryos/larvae). These 5 characteristics share a tail, a notochord, a single, hollow nerve cord, pharyngeal slits, and an endostyle (thyroid).

So, now that we've established that humans are from phylum chordata, we can narrow it down to what class they are in. Humans are in the class mammalia, meaning they are mammals. All mammals not only share those 5 characteristics of phylum chordata, but they also share characteristics that unite them with each other. They all have hair, mammary glands in females, and are endothermic.

So, while members of the phylum chordata share at least 5 traits, members of the class mammalia share at least 8.

I hope that makes sense!

b - the respond is innate and varies over time.

good luck!