Question

Choose the organism that has jointed appendages:

• A. Spider
• B. Comb jellies
• C. Sponges
• D. Rotifers

Answer 1

The correct option is A

Spider

The correct option is A.

Explanation of the correct option:

1. The spider's appendages are joined.
2. The word "arthropod" means "a creature with jointed legs." Arthropoda, the name of the phylum, refers to invertebrates with jointed legs and an exoskeleton.
3. A spontaneous evolutionary turning point was the emergence of jointed appendages.
4. Animals with robust bodies and spines would not have been able to move without joints.

Explanation of the incorrect option:

Option B:

1. They move by means of eight longitudinal rows of cilia.
2. Light is dispersed when the cilia beat, creating a rainbow of hues.
3. The pounding combs break the light into its component colors in a prismatic manner.

Option C:

1. Sponge mobility typically depends on water currents.
2. Cnidaria can travel by employing floats or sails, as well as by taking on the medusae form.
3. Mesoderm, which serves as a hydrostatic skeleton for Platyhelminthes, or other specialized structures like proboscis, suckers, or hooks, are how they move.

Option D:

1. Some rotifers are truly planktonic and free-swimming, while others travel around a substrate by inchworming, and some are sessile and reside inside tubes or gelatinous holdfasts that are fastened to the ground.
2. About 25 species are colonial (e.g., Sinantherina semibullata), either sessile or planktonic.

Final answer: Spiders have jointed appendages.