Why are sponges classified as sponges and not plants?

Sponges are classified as animals, specifically within the phylum Porifera, due to their unique cellular organization and lack of true tissues and organs, which distinguishes them from plants. They are heterotrophic, meaning they obtain nutrients by filtering water for food particles, unlike plants that produce their own food through photosynthesis. Additionally, sponges have a simple body structure characterized by porous bodies and specialized cells, further emphasizing their animal characteristics. Their reproductive and developmental processes also align more closely with those of animals than with plants.