Certain triploblastic animals such as acoelomates have mesoderm and mesenchyme in between ectoderm and endoderm. In addition, triploblastic animals with hemocoel have mesoderm and hemocoel in between ectoderm and endoderm. In contrast, triploblastic coelomates have mesoderm and coelom in between ectoderm and endoderm.
Diploblastic and triploblastic are two groups of organisms. As their names imply, diploblastic animals have only two germ layers while triploblastic animals have all three germ layers. So, this is the key difference between diploblastic and triploblastic. Generally, diploblastic animals are primitive metazoans, while triploblastic animals are advanced metazoans. Moreover, a notable difference between diploblastic and triploblastic is that the diploblastic animals do not have true organs and body cavities while triploblastic animals have true organs and body cavities.
Additionally, diploblastic animals show radial symmetry while triploblastic animals show bilateral symmetry. Therefore, this is also a major difference between diploblastic and triploblastic. The below infographic illustrates more information regarding the difference between diploblastic and triploblastic.
Generally, there are three germ layers in the blastula of vertebrates. They are ectoderm, mesoderm and endoderm. If an organism possesses all these three layers, we call it triploblastic. However, some organisms have only two layers: ectoderm and endoderm. They lack mesoderm. Jellyfish, comb jellies, corals and sea anemones are the examples of diploblastic animals.
Triploblastic organisms form all three primary germ layers — endoderm, ectoderm and mesoderm — during the gastrulation of the blastula. Mesoderm development is the characteristic feature in triploblastic animals. Mesodermal cells differentiate through the interactions of both ectodermal and endodermal cells.
Coelom is developed from the mesoderm. Inside the coelom, freely moving organs are formed, providing protection against shocks by fluid cushions.
These organs can grow and develop without the aid of the body wall. Mesoderm forms muscle, bone, connective tissues, circulatory system, notochord, etc. Other than that, endoderm develops into lungs, stomach, colon, liver, urinary bladder, etc.
Ectoderm develops into epidermis, hair, eye lens, brain, spinal cord, etc. All animals from flatworms to human are triploblastic. They belong to the clade : Bilateria and possess bilateral symmetry. Triploblastic animals are further divided into sections such as acoelomates, eucoelomates and pseudocoelomates. Acoelomates are lacking a coelom whereas eucoelomates consist of a true coelom.
Pseudocoelomates are composed of a false coelom. Eucoelomates can be again divided into two sections: protostomes and deuterostomes. Protostomes develop the mouth from the blastopore whereas the deuterostomes develop the anal opening from the blastopore. It is believed that diploblastic animals gave rise to triploblastic animals around to million years ago.
Figure 2: Differentiation of Three Germ Layers. Diploblastic: Diploblastic animals produce two primary germ layers, endoderm and ectoderm during gastrulation. Triploblastic: Triploblastic animals produce three primary germ layers, endoderm, ectoderm and the mesoderm. Diploblastic: Diploblastic animals are radially symmetric. Triploblastic: Triploblastic animals are bilaterally symmetric. Diploblastic: Diploblastic animals are lacking a mesoderm.
In between endoderm and the ectoderm, mesoglea can be identified. The body of these animals is made up of three layers, ectoderm, mesoderm, and endoderm. These layers do not remain separate distinct layers after development. They form different structures. They show a lesser degree of specialization.
They do not form specialized organs. The cells of these animals show a greater degree of specialization. They have specialized organs and organ systems. There is no special transport system for these animals.
Transport of material takes within the body by diffusion. They have a special transport system. It is the blood vascular system in most animals. There is no central nervous system in these animals. A neuron network is present.
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