what is the difference between the two phyla Platyhelmithes and Annelida?

Question

blues · Answer

There are quite a few differences but I'd say the most significant are:

1. Platyhelminthes are pseudocoelmate - they don't have a true body cavity - whereas Annelids do.

2. Sort of related to that, Annelids are segmented where as the organisms in Platyhelminthes are not.

roku · Answer

i dont understand the first point

roku · Answer

tape worms are segmented??

blues · Answer

Highly evolved animals have a coelem, or true body cavity. For it to be a true body cavity, the animal has to be triploblastic (all three types of body tissue) and the cavity has to be lined with mesodermal peritoneum. Usually the coelom is fluid filled.

Platyhelminthes are not that highly evolved. Don't have them. Annelids are.

blues · Answer

Do you know what phylum tape worms are in?

roku · Answer

those terms are sooo unfamiliar hopefully i will understand them soon enough

roku · Answer

they say that tape worms are flat worms hence they belong to the phyla platyhelminthes

roku · Answer

oke then i dont know how these worm things look like maybe that will help me to have a clearer understanding ccuz they also talk about leech, earthworm and roundworm belonging to the Annelida

blues · Answer

Actually, platyhelminthes is not psuedocoelomate. I think it is completely acoelomate. It makes no difference in the context of this discussion: it has no coelom and not even something which resembles a coelom, which distinguishes it from the Annelids which do.

And yes, the earthworm, round worm and leech do belong to Annelida. These animals all have a true coelom, so three tissue layers and a fully lined, fluid filled body cavity. And they are also segmented whereas the other classes and phyla you mentioned - platyhelminthes, cestoda, etc. - are not.

roku · Answer

sigh... my views:leech do not look segmented, neither did the  round worms however i thought that the tapeworm looked segmented

blues · Answer

It does not matter what it looks like on the outside. It does matter what it looks like on the inside.

But you are correct about the Cestodes, in as much as they do look segmented. In fact, they look so much like a segmented worm that the taxonomists incorrectly classified them as such for many years, until DNA sequencing showed Cestodes were not actually segmented.

roku · Answer

oke thnks Blu