The document discusses the characteristics of sponges. It notes that sponges are the simplest of animals, with no organs or senses. However, they are classified as animals because they are multicellular, their cells have specialized functions and lack cell walls, they are heterotrophic, and their larvae are motile. The document describes sponges' anatomy, noting they are filter feeders that draw water through pores using flagella. It also discusses sponge spicules, which form their skeleton, and their reproduction, which can occur asexually and sexually through budding.

1. Figure 33.2 Sponges

12. Figure 33.3 Anatomy of a sponge

14. Sponges are filter feeders:

21. http://www.pbs.org/kcet/shapeoflife/episodes/origins_explo1.html

22. Sponge Spicules

29. Sponge reproduction

30. Sponge reproduction asexual

31. Sponge reproduction asexual sexual

36. Sponges were likely the first true animal on planet Earth.

37. http://www.pbs.org/kcet/shapeoflife/episodes/origins_explo2.html