Feeding on Food Masses
Unlike filter feeders which feed in water, animals that obtain and eat solid food are not restricted to the aquatic environment, and show a great variety of adaptations related to their feeding habits. Animals like earthworms ingest the medium in which they live and digest the organic material in it as the material passes through the digestive tract. Many animals use methods for chewing and scraping to obtain food. Their food is often of plant origin. Numerous insects and other invertebrates as well as herbivorous vertebrates use these methods of feeding. Rasp-like structures known is radula is used by gastropods to scrape algae from rocs of to rasp through vegetation.
Figure: Sagittal section through head of gastropod showing the radula which is used to rasp off vegetation b) protraction of radula c) retraction of radula