(00:00-1:20= general information; 1:21 and beyond discusses Sponges)
Sponges
Sponges are one of the more basic marine animals, and don's even share many of the characteristics of what we would consider "normal" marine animal characteristics. Sponges usually don't move around in the water, they are typically anchored to a rock or coral reef. The only time they ever swim in their lives is when they are in the larval stage. Sponges are non- symmetrical and do not have tissue or a nervous system. They are "U" -shaped, typically having protective cells lining the outside and specialized cells lining the inside. Sponges are filter feeders, meaning they have pores that suck water in and their food (nitrogen) is filtered out by the flagella and eaten by the sponge. The sponge's osculum pushes the filtered water back out of the sponge. Sponges are responsible or lowering nitrogen levels in the water and keep the ecosystem clean.