This lab worksheet guides students through the external anatomy of a starfish, featuring labeled diagrams for both the aboral and oral surfaces.

Let’s go step by step through the lab instructions to help you complete your starfish dissection worksheet.

---

Step 1: Count and record the number of arms or rays.

Look at Figure 1 (the aboral surface — top side) of the starfish. Starfish usually have 5 arms, but some can have more. In this drawing, count each arm extending from the center.

→ You’ll see 5 arms.

So, write:
Number or arms: _5_

---

Step 2: Label Figure 1 (Aboral Surface)

You need to label three things on Figure 1:

- Central disc: This is the round part in the middle where all the arms connect.
- Arms: The long pointy parts sticking out — there are 5 of them.
- Madreporite: A small, hard, round plate on the central disc (usually looks like a tiny dot or circle). It’s often near one of the arms’ bases.

Also, feel for spines on the real starfish (or imagine them on the drawing) — they’re the bumpy dots covering the surface. Label those too as “spines” if asked, but the instruction says to label central disc, arms, and madreporite on Figure 1.

---

Step 3: Turn to Oral Surface (Figure 2)

Now look at Figure 2 — this is the underside (oral surface).

Label these on Figure 2:

- Mouth: Right in the very center of the starfish.
- Ring of oral spines: Tiny spines around the mouth — draw a little ring around the mouth area.
- Ambulacral groove: A line running down the middle of each arm on the underside — it looks like a trench or channel.
- Tube feet: Small soft bumps inside each ambulacral groove — they look like little suckers or dots along the groove.

---

✔ All steps completed!

Final Answer:
Number or arms: 5