13. A multicellular organism that has an exoskeleton and jointed legs belongs to which of the following groups?
Answer: C
An organism with an exoskeleton and jointed legs belongs to Arthropods.
Organisms that possess an exoskeleton and jointed legs are classified as arthropods. This group includes insects, arachnids, and crustaceans, which are characterized by these distinguishing features.
A) Mollusks
Mollusks are a separate group of invertebrates that typically have soft bodies and may possess a shell, but they do not have jointed legs or an exoskeleton. Instead, they have a mantle and a muscular foot, distinguishing them from arthropods.
B) Sea stars
Sea stars, or starfish, belong to the echinoderms and are characterized by their radial symmetry and lack of an exoskeleton or jointed legs. Their unique water vascular system and tube feet are key features that set them apart from arthropods.
C) Arthropods
Arthropods are defined by their segmented bodies, exoskeletons made of chitin, and jointed appendages. This makes them the correct classification for organisms that exhibit these characteristics, as seen in insects, spiders, and crustaceans.
D) Mammals
Mammals are a group of vertebrates characterized by fur or hair and mammary glands. They do not have exoskeletons or jointed legs, which are defining features of arthropods, making this option incorrect.
Conclusion
The correct classification for multicellular organisms with an exoskeleton and jointed legs is arthropods, as they uniquely exhibit these features. All other options fail to meet the criteria established by the question, as they belong to different groups with distinct anatomical characteristics.