Please, please answer the question. And honestly, I would much prefer if you typ
ID: 218375 • Letter: P
Question
Please, please answer the question. And honestly, I would much prefer if you type the answer down. Thank you!
I guess for clarification, summarize the discussion section of the article in such a way that a person can understand what the author is trying to convey without having to read the entire paper.
7. In their Investigating the Origins of Triploblasty article, Martindale and colleague present evidence that corroborates the hypothesis that the mesoderm of triploblastic animals (like urchins and us) derives from the endoderm of diploblastic animals (like sea anemones). What is the evidence they present, and how do they use it to support the "mesoderm-from- endoderm" hypothesis?Explanation / Answer
The formation of the germ layers begins at the Gastrula stage of the embryo when the cells begin to move and arrange themselves to form the body layers.
As we know, diploblastic animals have two germ layers-- ectoderm and endoderm while triploblastic animals have three germ layers-- ectoderm, mesoderm and endoderm .
Mesoderm played an important role in the evolution of larger and more complex organisms. Most of the body organs arise from the mesoderm of the embryo.
To investigate the origin of triploblasty, the developmental expression of seven genes were studied from Nematostella. Of the seven genes, six were found to be largely resticted to the endodermal layer, the gastrodermis. Only the gene named mef2 was found to be restricted to the ectoderm.
The temporal and spatial expression of these genes led the scientists to believe that they must play a role in germ layer specification. Furthermore, the predominantly endodermal expression of these genes reinforces the hypothesis that the mesoderm and endoderm of triploblastic animals coulld be derived from the endoderm of a diploblastic ancestor.
However, the evolutionary transition from diploblasty to triploblasty remains unclear. So, to deduce the molecular basis for the origin of mesoderm, the scientists compared the triploblastic , bilateral animals with the diploblastic outgroup animals.
Comparison of larval stage confirms the homology of mesoderm across the bilateral animals. The genes which control the germ layer formation and their origin further gives support to the " mesoderm from endoderm hypothesis" .