Echinodermata - Kingdom: Animalia - SS1 Biology Lesson Note
Echinodermata is a phylum of marine invertebrates that includes diverse organisms such as starfish, sea urchins, sea cucumbers, brittle stars, and sea lilies. Echinoderms are known for their unique radial symmetry and a spiny exoskeleton.
Image from newsweek.com
Image from byjus's.com
Here are some key features and characteristics of Echinodermata:
1. Radial Symmetry: Echinoderms exhibit a characteristic five-point radial symmetry, meaning their body parts radiate from a central point. This radial symmetry is typically organized around a central disk or body, with arms or appendages extending outward.
2. Spiny Exoskeleton: Echinoderms have a hard, calcareous exoskeleton composed of small plates or ossicles. These ossicles are often covered in spines or tubercles, providing protection and support for the organism. Some echinoderms, such as sea cucumbers, have a soft body with a reduced or absent exoskeleton.
3. Water Vascular System: Echinoderms possess a unique water vascular system, which is a network of fluid-filled canals and tubes that function in locomotion, feeding, and gas exchange. The system includes tube feet, which are small, suction cup-like structures that extend and contract to allow movement and attachment to surfaces.
4. Tube Feet: Tube feet are flexible, hollow structures that protrude from the body surface of echinoderms. They are operated by the water vascular system and are used for locomotion, feeding, and sensory perception. Tube feet play a significant role in the distinctive movement of echinoderms, such as the slow crawling of sea stars or the tube feet rows used by sea cucumbers for feeding.
5. Regeneration: Echinoderms have remarkable regenerative abilities, allowing them to regrow lost body parts. Some species can regenerate entire arms or even regenerate from a single fragment. This ability to regenerate is an important adaptation for their survival and recovery from injuries.
6. Pentaradial Symmetry: Although echinoderms exhibit a radial symmetry as adults, their larvae undergo bilateral symmetry during early development. As they mature, they undergo a transformation to pentaradial symmetry, with five or multiples of five arms or appendages radiating from a central body.
7. Feeding and Predation: Echinoderms exhibit a range of feeding strategies. Some species are herbivores, grazing on algae or detritus, while others are filter feeders, using their tube feet or specialized structures to capture plankton or suspended particles. Some echinoderms are predators, feeding on small invertebrates or carrion.
8. Ecological Importance: Echinoderms play important ecological roles in marine ecosystems. They contribute to nutrient cycling, serve as prey for various organisms, and influence community structure through predation and herbivory. They also have economic importance as a food source and are used in biomedical research.
Echinodermata is a diverse phylum with over 7,000 known species. The study of echinoderms helps us understand the evolution of different body forms, adaptations to different habitats, and the ecological relationships within marine ecosystems.