The key difference between Mollusca and Echinodermata relies on the habitat of the organisms belonging to these two classes. Molluscs live in both terrestrial and aquatic environments while echinoderms live strictly in marine environments.
Phylum Mollusca and Phylum Echinodermata belong to the Kingdom Animalia. There is a between Mollusca and Echinodermata in terms of morphological, physiological and behavioural characteristics. However, both molluscs and echinoderms are triploblastic, and they possess a complete digestive system. Biologists and taxonomists study characteristics of the organisms of each phylum in order to categorize organisms effectively.
CONTENTS
1. Overview and Key Difference
2. What is Mollusca
3. What is Echinodermata
4. Similarities Between Mollusca and Echinodermata
5. Side by Side Comparison – Mollusca vs Echinodermata in Tabular Form
6. Summary
What is Mollusca?
Phylum Mollusca belongs to the Kingdom Animalia and includes bilaterally symmetrical organisms that are triploblastic in nature. Molluscs live in both terrestrial and aquatic environments. The organisms belonging to phylum Mollusca show distinct segmentation. Their bodies have three distinct segments: head, visceral mass and ventral foot. Moreover, the ventral foot helps in locomotion.
A hard outer covering or a shell covers the internal cavity of molluscs. The shell is composed of calcareous material. Furthermore, the body cavity of molluscs is a hemocoel and blood circulates throughout the body via this hemocoel.
Figure 01: Mollusca
Molluscs show complete organization. They have a complete digestive tract which consists of a radula structure for feeding. The nervous system consists of a paired ganglia and connecting nerves. Moreover, molluscs have an open circulatory system with a heart and aorta. Molluscs respire through special structures in gills called ctenidia. They also have metanephridia for excretion. In addition, molluscs are bisexual animals, and their fertilization takes place either internally or externally.
Phylum Mollusca constitutes six classes: Bivalvia, Gastropoda, Cephalopoda, Monoplacophora, Amphineura and Scaphopoda. Therefore, phylum Mollusca includes organisms such as clams, octopus, squid and cuttlefish, etc.
What is Echinodermata?
Phylum Echinodermata, which belongs to the Kingdom Animalia, include triploblastic coelomates. They live exclusively in marine environments. Furthermore, they show radial symmetry, especially penta radial symmetry as seen in starfish. However, they do not show segmentation. They have flat, star-shaped or elongated bodies. Characteristic features of echinoderms include the presence of tube feet and a water vascular system, the presence of a mouth in the ventral side and anus in the dorsal side as well as papula for respiration.
Figure 02: Echinodermata
These organisms also show a correct organization with a complete digestive system. Even though they do not possess a complete nervous system, they respond to stimuli. Moreover, their circulatory system is reduced, and the blood has no pigment. Echinoderms are bisexual, and they show external fertilization.
Phylum Echinodermata constitutes five classes as Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea and Crinoidea. Starfish, sea urchin, sea cucumber are well-known echinoderms.
What are the Similarities Between Mollusca and Echinodermata?
- Mollusca and Echinodermata are two phyla of the Kingdom Animalia.
- They are triploblastic organisms.
- Also, both show complete levels of organization.
What is the Difference Between Mollusca and Echinodermata?
Mollusca and Echinodermata are two major phyla of the kingdom Animalia. Phylum Mollusca constitutes triploblastic hemocoelomates that live in both terrestrial and aquatic environments while phylum Echinodermata constitutes triploblastic coelomates that live exclusively in marine environments. So, we can consider this as the key difference between Mollusca and Echinodermata. Moreover, a further difference between Mollusca and Echinodermata is that the molluscs have a hemocoel while echinoderms have a coelom.
Furthermore, a significant difference between Mollusca and Echinodermata is that the molluscs have a segmented body while echinoderms do not show segmentation. Also, molluscs show bilateral symmetry while echinoderms show radial symmetry. This is a major difference between Mollusca and Echinodermata. Besides, an additional difference between Mollusca and Echinodermata is fertilization. While molluscs show both internal and external fertilization, echinoderms show only external fertilization.
The below infographic represents more information regarding the difference between Mollusca and Echinodermata.
Summary – Mollusca vs Echinodermata
Mollusca and Echinodermata are two phyla that belong to the Kingdom Animalia. They are triploblastic organisms. Molluscs have a hemocoel while echinoderms have a coelom. The key difference between Mollusca and Echinodermata is the habitat they live in. Molluscs live in both terrestrial and aquatic environments. In contrast, echinoderms only live in marine environments. They show a complex level of organization although their adaptations vary based on the environments they live in. Clams, oyster and squid, are some molluscs while sea cucumber, starfish and sea urchin are some echinoderms. Thus, this summarizes the difference between Mollusca and Echinodermata.
Reference:
1. “Phylum Echinodermata: General Characteristics and Classification.” Online Biology Notes, 18 Dec. 2018, Available here.
2. “Phylum Mollusca: Characteristics, Classification, Examples with Videos.” Toppr, 19 Sept. 2018, Available here.
Image Courtesy:
1. “Echinodermata” By E. M. Grosse – The echinoderm fauna of Torres Strait: its composition and its origin (1921) Clark, Hubert Lyman, 1870-1947 (Public Domain) via Commons Wikimedia
2. “Mollusca” By Veronidae – Own work (CC BY-SA 3.0) via Commons Wikimedia