Question: Which skeletal combination is characteristic of class Calcarea, also called Calcispongae?
1 Calcium carbonate spicules that may be needle-shaped or have three or four rays
2 Six-rayed silica spicules combined with a spongin protein skeleton
3 Non-six-rayed silica spicules combined exclusively with chitin
4 Calcium phosphate plates combined with a collagenous skeleton
1. The problem asks which skeletal combination is characteristic of class Calcarea (Calcispongae).
2. Class Calcarea sponges are known for their calcium carbonate spicules.
3. These spicules can be needle-shaped or have three or four rays.
4. Other options describe silica spicules or calcium phosphate, which are not characteristic of Calcarea.
5. Therefore, the correct answer is option 1: Calcium carbonate spicules that may be needle-shaped or have three or four rays.