Why do we consider adult sponges animals even though they don't move?

Adult sponges are considered animals because they belong to the kingdom Animalia, characterized by multicellularity, heterotrophy (obtaining nutrients by consuming organic matter), and the lack of cell walls. Despite their sessile nature, sponges exhibit essential animal traits, such as specialized cells for feeding and defense, and they respond to environmental stimuli. Their evolutionary lineage shares a common ancestor with other animals, further justifying their classification as animals.