Difference Between Metazoa and Eumetazoa

Key Difference – Metazoa vs Eumetazoa
 

Metazoa and Eumetazoa are two groups in the kingdom Animalia. The tissues of metazoa demonstrate true multicellularity without a true gut while eumetazoa contains tissues that are differentiated into true tissue forms. This is the key difference between metazoa and eumetazoa.

The animal kingdom has been subjected to various classification systems throughout history. Different scientists were involved in these processes. It was found out that all animals are evolved from a common ancestor. Classification criteria were developed through considering different physiological, structural and genetical aspects. Metazoa and Eumetazoa are two such groups derived from these classification systems.

CONTENTS

1. Overview and Key Difference
2. What is Metazoa
3. What is Eumetazoa
4. Similarities Between Metazoa and Eumetazoa
5. Side by Side Comparison – Metazoa vs Eumetazoa in Tabular Form
6. Summary

What is Metazoa?

Metazoa can be defined as a major division in the animal kingdom that consists of all animals except protozoans and sponges. Metazoa consists of animals with prominent true multicellularity. They possess nerves and muscle tissue. But they lack a true gut. Metazoa are said to be evolved from protists roughly 700 million years ago.

The evolution of metazoans is described through two theories. But one theory is highly discredited due to invalid proof. The other theory proposed by Earnest Haeckel in 1874 is considered as valid. In this theory, he proposed that multicellular organisms contain a colonial ancestor.Most of the genomes of animals of metazoa are already sequenced in the NCBIs genome category.

Figure 01: Metazoa

Metazoa animals are heterotrophic since they are unable to fulfill their energy requirements by themselves. Therefore, they depend on other animals or products of other animals.In the context of their life cycle, they have a diploid (2n) life cycle primarily. Haploid (n) male gamete (sperm) and a haploid (n) female gamete (egg) are fused together and result in diploid (2n) zygote that develops into a multicellular embryo. The unique feature of metazoans is the cell containing an extracellular matrix that is made up of collagen adhesive glycoproteins, proteoglycans, and integrin.

What is Eumetazoa?

Eumetazoa is defined as a subkingdom of multicellular animals excluding Placozoa, Porifera (sponges) and extinct life forms such as Dickinsonia.  The characteristic features of eumetazoans include the presence of true differentiated tissues that are arranged into germ layers and the presence of an embryo that develops through a gastrula stage. Eumetazoans mainly consist of animal groups such as Ctenophora, Cnidaria, and Bilateria.

Different phylogenists speculated the fact that, the evolution of sponges and eumetazoa took place from separate unicellular organisms. It means that the whole animal kingdom is not composed of organisms that are evolved from a common ancestor. But recent genetical analysis proved the fact that the animal kingdom descends from a common ancestor.

Figure 02: Eumetazoa

In the context of a formal taxon, eumetazoans are considered as a sub-kingdom. It is within the kingdom Animalia. Most of the times, eumetazoa is not included in the classification schemes.

What are the Similarities Between Metazoa and Eumetazoa?

• Metazoa and Eumetazoa are two groups in the kingdom Animalia.
• Both exclude sponges.
• Both are subgroups.
• Multicellular organisms are present in both groups.
• Organisms of both Metazoa and Eumetazoa are heterotrophic.
• Both evolved from a common ancestor.
• Tissue differentiation is present in both.

What is the Difference Between Metazoa and Eumetazoa?

Summary – Metazoa vs Eumetazoa

Metazoa and Eumetazoa are two groups of the animal kingdom. Both groups contain animals that are heterotrophic and are derived from a common ancestor. Metazoans are a major group of the animal kingdom while eumetazoans are a subgroup. Metazoans lack a cell wall. They possess an extracellular matrix that is made up of collagen adhesive glycoproteins, proteoglycans and integrin. Eumetazoa possesses differentiated tissues that are arranged into germ layers and the presence of an embryo that develops through a gastrula stage. This is the difference between metazoan and eumetazoa.

Reference :

1.Peterson, K. J., and N. J. Butterfield. “From The Cover: Origin of the Eumetazoa: Testing Ecological Predictions of Molecular Clocks against the Proterozoic Fossil Record.” Proceedings of the National Academy of Sciences, vol. 102, no. 27, 2005, pp. 9547–9552., doi:10.1073/pnas.0503660102.
2.“Metazoa.” Metazoa – Microbewiki. Available here
3.“Metazoa.” Encyclopædia Britannica, Encyclopædia Britannica, Inc. Available here

Image Courtesy:

1.’Metazoan Phylogenetic Tree’By Schierwater B, Eitel M, Jakob W, Osigus H-J, Hadrys H, et al. – Figure 2 (CC BY 2.5) via Commons Wikimedia  
2.’14037454758′ by Phylogeny Figures (CC BY 2.0) via Flickr

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